Flange bearing, plywood equatorial Part 2.

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An update: I just found a 40cm, 16" length of 50mm, 2" stainless steel shafting hidden in my metal stock which appears to be more than adequately robust. Certainly of ample girth when compared with the relatively "flimsy" 31.75mm or 1.25" of the Fullerscopes MkIV when lying alongside. Or the even skinnier 1" shafts of the MkIII. So I have the potential for quite a decent PA axis. Unfortunately it isn't long enough for a Declination axis or I could have used 2" for the Dec and 60mm for the more heavily loaded PA axis.

The best commercial, equatorial mountings use hollow shafts and pre-loaded, opposed, taper [conical] roller bearings. Often with at least some degree of circular "plate" bearing to add extra stiffness. Home made plate bearings are possible but need considerable care to avoid too much friction.

A bit of searching online suggests that steel weighs three times as much as aluminium but aluminium is 1.5x less stiff than steel. So a 2" aluminium shaft would be as stiff as the present 1.25" shafts in steel. While stainless steel is no more stiff than ordinary steel. If I wanted to change 2" steel shafts over to aluminium [for lightness] I'd need to use 75mm or 3" Ø. Unfortunately, there's a bad case of 'swings and roundabouts' going on here. The aluminium shafts would be slightly lighter than steel but the bigger flange bearing housing would be much heavier than the smaller size needed for 2" steel shafts!


An old industrial sized, grinding wheel base offers potential as a sturdy, cast iron, PA axis when mounted on a suitable polar altitude 'wedge.' The 60mm pipe is slightly too large to leave much room for bearing shells. While the original, self aligning, journal ball bearings considerably reduce the potential diameter of the shaft. I thought I might manage to fix slips of Teflon/PTFE between a shaft and casting but it wasn't meant to be. Sadly the dimensions of the casting to not readily lend themselves to a large central wormwheel. By the time I have added bearings I might just as well have used two, modern, pillar block bearings on a hefty support plate.

 A shame because it has the looks [if you have a vivid imagination] of something from the classical, Victorian, telescope making era. More "thinking furiously" is obviously required before I commit to doing anything with it. Turning brass plugs to house journal bearings for the 50mm shaft is doable. My lathe isn't large enough to turn a flange once it is permanently mounted on the shaft. So I'd have to consider practical options for clamping or grub screw fixing of a tight fit. Or go back to the flange bearings and plywood housings idea.

Metals [including stainless steel shafting] are readily available from dealers on eBay[UK] but the international postage inevitably makes a bit of a dent. The nearest scrap yard has lost interest in selling to private customers and is rarely open these days anyway. I had some nice brass stumps in all sorts of sizes from them over the years. Danish metal stockists sell stainless steel, round bars for about the same prices as eBay[UK]. Though not remotely as cheaply as scrap yards. Paying well over £100 [equiv] for a length of 50mm, 2" shafting for a mounting axis just goes completely against the grain. Especially for a hardened scrap yard and flea market re-cycler like myself.

I have discovered a new way of holding the axes of a mounting together. A superb home-made mounting with 2" shafts on Cloudy Nights ATM forum shows the use of multiple taper locking bushes to good effect. These split, taper locking bushes are available in metric or imperial sizes which grip onto a shaft using opposing tapers and grub screws. The tapered bush can hold a sprocket, pulley or drive flange/coupling firmly onto a plain shaft. The bush with flange can be bolted onto a plate to provide a declination axis base for the bearings. The taper can be unlocked by removing the two locking grubscrews and then screwing one of them back into a third hole intended for the purpose. This pushes the taper apart. Finding these bushes are readily available, in many shaft sizes, greatly simplifies the construction of an accurate GEM. Finding the matching flanges seems to be slightly more difficult.

In passing, I noted from the DR NEWS website that Denmark is enjoying 17hours of sunshine at this time of year. It's no wonder it never gets really dark! I usually go to bed around 11pm and look out of the window at a blue sky with Jupiter and Mars hardly making an impression. Not quite Land of the Midnight Sun but close enough, at least for a while, at 55N.

I am presently struggling with my vintage, equatorial mountings and the drives in particular. The worms are constantly rusted and their housing support woeful. I could replace them with a pair of larger Beacon Hill wormwheel sets and matching motors. Though this still leaves me with the limitations of the Fullerscopes mountings. The 7" f/12 is really pushing it beyond its useful capacity. If I ordered wormwheels to fit the MkIV then I could not increase the core diameter later to match a heavier mounting. Concentricity is vitally important in accurate wormwheels. So one can't just turn up a packing bush to match a smaller shaft. Besides which, the clutch is usually a nylon plug in the wormwheel boss. Which would no longer function as intended without an extended adjustment screw passing through the bush.

A Beacon Hill MkII uses 1.5" shafts. An improvement on the Fullerscopes 1.25" but not by much. D&G optical suggest 2" shafts for refractors in the 8" size range. A complete Beacon Hill GEM with 2" shafts and pillar block bearings would weigh a ton and the freight charges to Denmark would have to be considered. Too many options to consider even without the consideration of the likely expense. 

Building a 2" shaft, plywood GEM using Beacon Hill wormwheels would be much cheaper. Even with having to buy the flange bearings, taper bushes and stainless shafts at Danish retail prices. The question is whether it would be as "stiff" as a Beacon Hill mounting in actual use. I have to make a decision because using the MkIV [and MKIII]  is proving extremely frustrating now that I am trying to image the Solar system.

A greater margin of strength would allow me to add finders and subsidiary telescopes and to stop worrying about the weight of it all. I could even balance the telescope properly at half way instead of the usual nose heavy look. If I could have the 7" permanently mounted I could concentrate on imaging the Sun. It requires much less stringent open skies compared to the planets and the Moon. These could be imaged when they present themselves in suitable directions and altitudes. Moreover the neighbours' security lights could be completely ignored for solar imaging purposes. Now I just need to remove the house from the Solar light path without making ourselves homeless. 

Click on any image for an enlargement.

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A flange bearing and plywood equatorial mounting.

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 23rd May 2016. The Fullerscopes MkIV mounting had found its limits with the 7" f/12 refractor and 10" f//8 Newtonian. Having the Skytracker VFO pack up on me merely confirmed what I already knew. I needed a much bigger equatorial mounting to cope with the considerable moment arms of such long and rather heavy, OTAs. Friction and flexure were becoming a bore when trying to point the telescope. Or worse, when trying to center an object in the field of view. For imaging the MkIV's only advantage was having a variable drive. Which was now gone. Everywhere else it fell down on the job. 

I was quite tempted by the well proven pillar block bearing mountings. Beacon Hill has a successful mounting which uses pillar block bearings. What put me off was the need for considerable [and very very heavy] metal sections to keep the bearings aligned without twisting. Very large pillar block bearings are also very heavy due to their cast iron housings. 10kg [20lbs] each if I was to realise my ideal mounting with a considerable margin of stiffness without shaft flexure. Then I realised that going that large was unnecessary and shafts somewhere about 60mm were ample.

While searching for affordable pillar block bearings in the small ads website I discovered that flange [or pillow block] bearings were about the same price for the same bore when new. Moreover they [flange bearings] had some rather desirable features in comparison with the more popular pillar blocks. They could be easily attached to plywood without offset, cantilever or torque issues raising their ugly heads. The pillar block is offset from its support plate and the plate then tilted all over the place. The offset or cantilevered forces have to be countered with little more than a thick steel [or aluminium] support plate. The 60mm flange bearings weigh about 5kg or roughly 10lbs each. Though plastic flange housings are available too they are probably more expensive than cast iron.

While solidly made, birch plywood boxes with a flange bearing at either end has no great desire to twist. The boxes are as stiff, for the same weight, as solid aluminium if properly made.

The boxes could be laminated as thick as I desired to fill all the empty air spaces inside. Provided of course there was room for the axis shafts to turn. And all without adding much extra weight but adding considerable extra stiffness. Since the "packing" plywood would be within the visible outer shell it would consist of smaller pieces with lower weight.

Only waterproof wood glue would be necessary to hold it all together without any need for bolts, screws or nails. Or worse, welded, heavy steel plates and/or girders! I might actually be able to lift the major components of a plywood mounting without needing a crane or block and tackle! Nor a week's bed rest afterwards!

Furthermore, the flange bearings could be physically connected to each other and the surrounding box housing via lengths of sturdy studding. [Threaded rods] The bolt holes in the flanges are always generous in diameter and can easily be enlarged with a drill if needed. All this reinforcement would further increase the strength of the solid plywood boxes by compression and by virtue of the well spaced studs themselves while under tension. No loose sections or panels could ever detach from the axes boxes by accidental overloading.

Four, brand new, flange bearings can be had for about £60 in the 60mm bore size. [2 3/8" Ø] Easily enough to support either of my long OTAs with plenty of stiffness to spare. I seemed to be onto a winner!

Of course I still needed to source suitable shafts and  large wormwheels. I'd have an incredibly strong mounting for much the same cost as the lowliest, budget equatorial only suitable for a small refractor. I would prefer thick-walled tube for the axes to save a little weight without reducing stiffness. I shall have to ask around the local smithies to see what they have. 

The Polar Axis housing box would be supported and pivoted in a thick, reinforced, plywood fork to allow adjustment of polar altitude. A turnbuckle would provide fine adjustment to achieve polar altitude accuracy. Through bolts, or studs, using large, load-spreading washers, would then clamp the whole mass together as a solid unit to the thick base of the fork. All this requires is for the clamping bolts or studs to be raised or lowered to clear the axle.

The polar housing and fork will be bolted to the thick, welded steel, pier flange. Thereby safely avoiding all the usual bottlenecks seen in many commercial mountings. The center of gravity of the mounting [and counterbalanced telescope] lies directly over the pier pipe and thus avoid the usual cantilevered forces.  

The Fullerscope MkIV's flimsy, cast fork and tiny altitude locking screws are by far its weakest features. Making the polar tilt pivot in direct line with the polar axis made it impossible to have a through bolt. So it relies on short threads cut in very soft, cast alloy. The fork is thin and hollow section and readily crushed by over-tightening the existing and undersized, pivot screws. As I discovered when I re-cut the threads for much larger, stainless steel pivot bolts.

The plywood axis housings and fork could be painted for protection against the weather or clad in thin aluminium. Exposed, wooden windows can last for years with just a coat or two of good quality protective paint. So a waterproof, birch plywood mounting kept under a cover should last for as long as I will ever need it. 

Large and thick metal flanges would join the shafts directly to the plywood boxes to avoid flexure in these most highly loaded areas. I have some 180mm, 7" diameter aluminium round stock just looking for such a useful purpose. The shafts could be slightly beveled and hydraulically pressed into the pre-drilled and turned flanges. Though consideration for bearing removal will have to be considered.

The saddle can be made to any desired length from some heavy, aluminium U-form girder hanging around in my metal stock collection. Inverted over the preformed flange and with standard hinged rings fitted on the flat side it will be as strong as any cast saddle.It will also reduce overhang beyond the upper bearing which is a disaster in some mounting designs. Every millimeter of overhang requires extra counter-weighting and introduces unsupported shaft to potential flexure.

I could probably source an 8" diameter flanged and galvanized pier pipe, as long as desired, from an architectural ironwork manufacturer's heap of discarded projects.

Click on any image for an enlargement.

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18th May 2016 iCap/Neximage 5 completely flakey!

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I went out at 11 pm [CET] to have a look at the Moon and Jupiter with the 7" stopped down to 6". With the Skytracker control box still unwell I had the RA motor running straight off the mains. A quick check with a neon test screwdriver proved that there was nothing live about the mounting. The insulation of the wooden telescope rings would have helped to protect the OTA anyway. Interestingly, the computer case produced a nice warm glow!

Both my targets were rather low and there was considerable thermal turbulence. I decided to take a chance and see if I could capture some more videos with the Neximage 5. The thermal agiation and image softness was unbelievable! Expecting anything to come from stacking and processing the videos was probably an exercise in delusion! 

That was when the trouble started. Every time I managed to capture a file the camera would lose interest in living. It would change its settings from Y800 to RGB32 and go offline! I had to keep pulling the USB plug to get it to register the lack of images in "Live" mode. This would put a message on the screen and "Refresh" would then allow the camera to be recognized via "New." Though often this trick would not work and no image appeared on the computer screen. I was using a short [2m] USB extension and tried several others to see if it helped. One would not work at all! Perhaps I need a powered cable? 

Even when I had an image on the screen the usual problem cropped up: It was very difficult to focus with the very high "magnification" provided by the camera in 640x480. Using 4x binning the image scale is still very large and focusing is anything but easy. After I captured each video the camera would promptly turn itself off. So the whole "wake up" palaver had to be gone through yet again. I eve tried setting both boxes to RGB32 but it did not help. Again and again there would be a flash on the screen and a message would come up that despite being "live" no images seemed to be available.

I kept this up for an hour, or more, on the Moon but did not capture a single video of Jupiter. The camera also behaved erratically when I was capturing files of the Mercury transit and sunspots. I was always careful to dress the first cable from the camera along the OTA to avoid any load on the tiny plug in the Neximage 5 camera socket. There does seem to be a signal problem in the present chain. The camera is usually offered [by dealers] with a long, powered USB cable but I dd not bother since I already had so many old USB cables to play with. There is also the matter of being near enough to a computer screen to actually focus manually. If the screen is any more distant there would need to be a powered focuser!

Despite everything this is my very first Lunar image from the Neximage 5 via Registax. The image just above is a single frame from the video and one of the better ones at that. On the computer screen the image was boiling continuously and furiously with frequent totally fuzzy blanks where any focused image was lost completely. Most of the time the limb was completely invisible or an inch wide, multilayered arc. How Registax managed to drag anything from that grey mush is utterly amazing! 

Perhaps the problem is one of not using USB2 [or even USB3] rather than "standard" USB 1.1? That would mean I'd need to add a new USB2 board to my Vista computer. Oh, but I had! But that was around the back and would involve completely reorganizing everything in the pitch dark with a torch held in my teeth.

My main, W10 PC indoors has a couple of USB2 and two USB3 sockets so I could do a camera test indoors without having to move either computer. There remains a question over iCap updates without a continuous Internet connection on the old Vista computer. A laptop would be very useful indoors to allow dual simultaneous browsing while I am using the indoor PC for blogging and image preparation. The problem is the considerable added expense of a laptop to the already considerable astro imaging budget. I'm really not sure a tablet has any relevance to my kind of imaging.

Testing with the newly purchased USB 2 cables proved that the difficulties lay with the supplied USB cable. The plug seems to be quite loose on the Neximage 5's own mini-USB socket. I tried a 2 meter USB 2 to mini USB 2 and then added a 3 meter USB2 adapter/extension cable. [Male to female.] Both systems worked flawlessly with the Neximage 5 using iCap2.3 on both computers. I can only presume that the supplied cable was interrupting the signal from the camera via the 1.1 sockets on the old front panel. Though it never occurred to me at the time. I certainly shan't make that mistake again!

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May 12th 2016 Drive disaster!

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Disaster has struck! The 8 hours of driving the heavy 7" refractor on the MkIV mounting, for the Mercury transit, has damaged the synchronous Crouzet motor on the polar axis worm/wheel drive. It now vibrates instead of running normally. I presume there is some small spring which sends the motor turning the correct way. I dismantled the motor from the worm housing and finally its clip -on gearbox. Turning the shaft in either direction with the power connected does not help. Melted grease seems to have been forced through the worm housing bearing nearest the motor. The worm spins freely without end shake. Though the same probably cant be said for the engagement of the worm with its original bronze wormwheel. There was a lot backlash so I tightened it up. This may have been too much for the Crouzet motor and it may have overheated. 

The motor is still listed for an incredibly high price [£130+p&p] from specialist UK motor dealers. For about the same money I could buy a new worm wheel set from Beacon Hill. Then add their synchronous drive motor for use with the Fullerscopes Skytracker VFO adjustable speed drive system.

The 180mm, 7" 359-toothed Fullerscopes wormwheel is about 50 years old and made of bronze. It is still in usable condition but the worms are of plain steel and rust readily in normal [outdoor] use. I have had to wire brush the rust off repeatedly over the years I have owned both Fullerscopes mountings. [MkIV & MKIII] While Beacon Hill's worms are of stainless steel. A larger wormwheel could be added to the MkIV to reduce the torque required to drive the Polar Axis. This would force the use of a Beacon Hill motor because their tooth count is lower requiring a higher RPM on the drive motor to compensate. A slight doubt remains whether the Fullerscopes VFO could easily cope with the Beacon Hill motor. 

The difficulty with the Fullerscopes MkIV is the that both wormwheels are recessed to use up less axis/shaft space. This aids stability by reducing overhang beyond the bearings and also reduces the need for extra counter-weighting. The MkIVs use an internal rim clutch with Nylon pad forced into contact with a threaded rod and radio knob. Beacon Hill use a similar "clutch" pad but does not give any information on whether is is manually adjustable or having a "fixed" degree of friction. Beacon Hill's wormwheels seem to use a standard boss like a pulley. Which looks to be removable on some wheels. No doubt Barry could be persuaded to turn an internal rim on a larger boss to allow the MkIV's clutch to continue in the original form. Perhaps a shaft gripping pad is superior?

Another worry is that Fullerscopes uses [I think] a double-transformer, fully isolated mains system while Beacon Hill uses 24Volts. [Or so I believe.] It would not be too difficult to add a 250/24V AC reduction transformer but it adds unwanted complexity in a damp environment. Perhaps a 240V AC mains motors could be supplied instead? Is the old MkIV really still worth its considerable weight in gold? The Beacon Hill MkII mounting is not hugely expensive for a 1.5" pulley block ball bearing shaft to the Fullerscopes MkIVs 1.25" plain shaft bearings. Though two pairs of worms and wheels must be added to the asking price. No other, remotely affordable, modern mounting could possibly cope with such a huge and heavy, classical refractor.

I'm not sure I really want to get involved in making another mounting even if I could obtain the pillow block bearings cheaply secondhand. It would want at least 2" shafts and needs solid bosses to connect the axles and saddle. Then add the two pairs of large wormwheel sets and drive motors...

So many questions raised from the failure of one, rather old, Crouzet synchronous motor!

An update: It is worse than I thought! The motor spins happily when connected directly to the mains. But the shaft and pinion oscillate rapidly when fed by the Skytracker VFO. Checking the connector block in the motor leads, with everything connected as normal, shows only 70V AC on my DMI.

I opened up the control paddle and the PS box but there are no burnt or broken wires.  Nor any sign of anything unusual to my eyes. I claim absolutely no expertise at electronics beyond the simplest testing. I'm more of a mechanical type. I even dismantled the motor DIN plug from the main PS box and this showed nothing awry. The motor showed the same symptoms upon reconnecting again. Presumably it lacks enough power to turn reliably.

At least this gives me the option of a single speed polar drive if I connect the motor to an extension lead. Perhaps with a switch in-line.

I am most grateful to a fellow amateur astronomer with advanced electronics skills for offering guidance to repairing the damage to the electronics. The power transistor at top center of the PCB has clearly overheated. Possibly due to poor heat sinking. It seems I have been drawing too much current from the control box to overcome high levels of friction in the bearings and wormwheels of my MkIV mounting. Fortunately the TIP31A transistors are readily available at low cost. I just hope my skills at soldering are up to the task. Or I may do more damage than I manage to repair!

Update: In the absence of the worm the MkIV's RA  axis can turn freely. The axis brake only works via the worm's resistance to the wormwheel turning against its nylon pad brake. This makes the MkIV's use unnecessarily difficult. So I have replaced the RA worm, housing and motor. A simple mains extension lead will drive the motor until I have [hopefully] made repairs to the VFO drive control system. I have left the motor to run and checked the backlash and freedom repeatedly and all seems well. It is just that I no longer have any capability to adjust the speed of the RA drive nor that of the the Dec axis via the paddle.

Update 2: I removed the burnt transistor on the Skytracker PCB and replaced it with a new one. I have yet to test it or apply mains electricity.

Update3. The new transistor overheated too! 

Click on any image for an enlargement.

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10th May 2016 Some first imaging results.

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Having shared my afocal 'snaps' in the last post I tried my luck with Registax 6 on some of the Neximage 5 videos I took yesterday. It was quite fun working on my old, Vista computer in the shed. Apart from the wasps looking for nesting sites!

I started with Jupiter because the clear contrast should have been easier to work with for a complete beginner.  I have to admit to being rather pleased with this very first successful outcome of using Registax. This image came from my 90mm f/11 Vixen 90M, on the vintage Fullerscopes MkIII mounting, using the Neximage 5 camera. None of the original frames showed anything but two fuzzy stripes on a soft and fluffy ball. None of this detail was seen visually. Merely fleeting moments of two darker belts. Colour versions should follow when I attain greater mastery of the processing software.

My first image of Mercury is a bit overblown in the Registax processing. There are signs of CA surrounding the planet thanks to the enormous image scale. See my last blog post for full sun images showing the tiny size of Mercury relative to the sun's disk. Some surface structure of the Sun also appear in the background.

Remember that this image was taken with an achromatic refractor. 180mm, 7" f/12 stopped down to 150mm, 6" working at a nominal f14.4. iStar's claim of 35% improvement in CA for their R35 optics must surely be proven by the quality of these early images?

The sun was dominated by a large, almost central, sunspot group during the entire transit. I captured several videos of this group using my iStar refractor using a Baader AstroSolar foil filter. The Neximage 5 camera was mounted on extension tubes rather than using the star diagonal to avoid unnecessary optical components. 

Now I am wondering how I managed to capture two different sized sunspots.  It is just possible that one was taken using a different resolution in the iCap camera settings. I was experimenting some of the time to see how it affected image quality. The normal 640x480 setting was changed to 1024 x 768 to get a wider view and hopefully, to reduce the incredible thermal turbulence visible on the screen. Both images are saved from Registax without any further 'adjustment.'

 These first imaging results are certainly encouraging. Had I failed dismally at the first fence I might have lost my early enthusiasm. It just goes to show how a home-made telescope on a half-century old, vintage mounting, wielded by a complete beginner at imaging and using Registax can achieve reasonably acceptable results.

I am most grateful to my fellow amateur astronomer in the UK who's selfless guidance has helped me to clear many potential hurdles.

Hopefully, with much more practice and experience I can achieve better results.

This image has been stacked and processed in Registax as before but then [mis]treated in PhotoFiltre. Dust Reduction and changes in gamma and contrast and cropping have helped bring out more detail. Critics might argue that it has been over-baked but I am only a complete beginner at this and am quite prepared to publish my mistakes. 

I have now been given some notes by my imaging adviser in the UK and can fill in some of the missing gaps. Progress is not helped by using two computers. One of which has the AVI files but no connection to the internet and is in the shed. I am ferrying processed images back to the indoor computer on a USB stick for publication on my blog.

This last image has been through PIPP before processing in Registax in colour. Early days yet and I am still finding my way around the software.

Click on any image for an enlargement.

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10th May 2016 Mercury transit impressions.

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One could not have asked for clearer skies than yesterday for the Mercury transit. There were a few clouds after lunch but they never blocked the sun. After that the day remained cloudless until well after 9pm. It was also very warm at 72F which required a careful choice of clothing to avoid being cooked alive with sunburn over an 8 hour session out of doors. A dark, long sleeved, cotton shirt provided protection without too much warmth. A pair of shorts helped me to stay reasonably cool while still exposed to wind and sun. Later on the deliberate choice of situation provided vital shelter thanks to our high garden hedge.

 

I had to drag the massive pier along the drive past the house to place it outside the garden to have any hope of an unobstructed view. Otherwise thermal currents rising from our own roof would have dominated the proceedings from beginning to end. Then I had to carry the 8' long, 45 lb refractor out to the mounting and lift it up into place. The transit started at about 13.10 CET with the sun at about 53 degrees altitude but I had already set everything up well over half an hour earlier to be ready. 

The computer for capturing AVI files from the Neximage camera rested on the footplate of a folding workbench. This was placed just inside the gates to provide some shelter from the sun while remaining close enough to the telescope. Focusing and centering an object on the screen required a clear view but still teased at intervals. The small monitor sat on a heavy piece of kitchen working surface to provide greater area for the mouse and keyboard without any risk of it lifting in the gusty wind. In fact the easterly wind proved to be a nuisance at times while capturing videos. Though one cannot complain if the sky is clear when many others had cloud. 

Plans to use multiple instruments were shelved so that I could concentrate only on the 7" on the MkIV mounting. Though this meant removing and refitting the Neximage 5 camera at intervals. I wanted to practice taking afocal 'snaps' in between capturing AVI files. The refractor was stopped own to 6" @ f14.4 nominal and fitted with a Baader AstroSolar film filter.

iStar claim a 35% extension of effective focal length with their R35 lenses to bring a 6" to f/19. False colour was indeed very low with hardly a fringe at focus when used visually. I worked my way up through my secondhand eyepiece collection and reached 175x without Mercury losing sharpness! There was no sign of increased CA due to magnification. Turbulence was another matter altogether despite the large lawns and miles of fields surrounding my observation site. The nearest building was a hundred yards way in the direction of the sun.

The image scale through the Neximage 5 Camera was far more than was strictly necessary or even desirable for solar work. When used in the 5MP mode with 4x binning for centering it all looked well. When binning was disabled the camera stared at only a tiny area of the Sun. The central sunspot group or Mercury each filled the field of view. Capturing both together was completely impossible in the Y800 640 x 480 capture mode. The sunspots and Mercury seemed to be floating on a complex, seething jelly. Even when I had temporarily lost Mercury outside the Neximage 5's field of view the surface detail was easily enough to be seen passing across the computer screen.

As previously discovered, the Canon Ixus 117 camera has a mind of its own when taking afocal images of the sun. It seems quite unable to relax and take an image regardless of settings. The sun's image was often completely out of focus or heavily shadowed with dirt and dust shadows. I cleaned the eyepieces but that wasn't the problem. I removed the star diagonal and fitted extension tubes but the star diagonal wasn't the problem either. Still the debris shadows persisted projected onto the sun's image. I cleaned the camera lens repeatedly but still the shadows spoilt the images. From previous experience with the TZ7 I now believe the debris is on the sensor or in the Canon lenses. I have dismantled the TZ7 several times to clean debris from its sensor. The camera's zoom action seems to suck dirt into the optics where it lodges permanently in the field of view. I really ought to do a close examination of the unwanted shadows when rotating the camera and the eyepiece separately. Hindsight is always so perfect!

In retrospect I could have used the 5MP still image capture option for recording Mercury's progress on the Neximage 5 but the scale would still have been very large. My first Sony compact digital camera always took fine solar images without any effort at all. I had deliberately chosen the Ixus for afocal astro snaps because of its small clear aperture and short zoom better matches ordinary eyepieces.

Initial images show the absolutely tiny size of Mercury relative to the Sun. Trying to learn how to use a brand new camera during a rare transit may not be wise but it provided plenty of forced practice. The MkIV showed it age and lack of regular maintenance in lagging badly between reaction to its control paddle button pressings. A quick adjustment with a hex key solved some slack in the worm drive housings. Interestingly, the view through the Neximage 5 camera was extremely rapid to the slightest touch of a control button when in capture mode setting. Which only goes to emphasize the high magnifications involved.

The bottom line is: Do not expect to become a world famous astronomical imager on day one! Particularly if you are relaxed [slapdash?] about any aspect of your instrumental set-up. It take precise adjustments to focus, collimation and mounting alignment. Now add an intimate familiarity with the camera, its capture software and image processing software like Registax.

Mercury, the Sun's limb and its spot groups provided plenty of hands-on, eyeball practice yesterday. I gained a little more useful experience with the camera and iCap but climbed perhaps only one rung on the steep learning curve in Registax.

Not least, solar imaging needs a reasonable, non-reflective computer monitor. One within easy reach of the telescope focusing knobs. Or preferably a motorized focuser to allow one to peer closely at the screen from the shelter of a decent solar screen. Mercury was a tiny black dot when seen visually through the eyepiece. But became a bouncing, gigantic, gyrating ball of fluff above a blazing bonfire seen across a shimmering desert through the Neximage 5! I kid you not. Perhaps I should have hoped for cloudier conditions to keep thermal issues at bay?

Perhaps it is easier with shorter telescopes? But then you'd only have to add a Barlow to make the image huge enough to actually see anything! It was a fun, interesting and rewarding experience despite all the apparent negativity mentioned above. I only write it all down to remind myself what I will probably have forgotten by next time I go out there and try and capture what is happening up in the sky. Familiarity will come with practice. It just takes longer at my age. I have taken my first faltering steps on what is often claimed to be the long road to financial ruin that is astro imaging. Those who have already proved their imaging competence have gained a lot of respect from me.

Click on any image for an enlargement.

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Imaging? At my age?

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After many years of taking afocal 'snaps' at the eyepiece the Mercury transit tempted me to get involved in imaging at the basic 'entry level.' Of course I left it far too late to become truly familiar with the camera or the vital software involved. The dinky little Neximage 5 camera arrived at lunchtime on Saturday and the transit is on Monday. Another roundtoit! I had always hoped to use my Philips webcam cameras but can't get the drivers to work with W10! The price step up to the "proper" imaging cameras even for the Celestron has put me off getting involved until now.

Needing something to practice on indoors and preferably near the PC I set up the 70mm Bresser refractor on its mounting and tripod. Then pointed the little telescope out of the window at a distant target after loading the supplied iCap and Registax 6.1 software from the disk. Focusing was an issue due to the tiny field of view even at maximum resolution and picture size. This narrowness in visible area really has to be experienced to be believed!

My target was a modestly sized, car trailer at exactly 300 yards [according to Google Earth] At full 5M image size and 20% I could just get the trailer body in view. When reduced to 640x480 @ 100% I could only get perhaps 2 wheel widths into the view box on the iCap screen. Bear this small field of view in mind when you are trying to find a tiny object in the very big sky!

I spent a couple of hours familiarizing myself with the iCap 3.1 software and capturing a few videos. Repeatedly watching an excellent series of instruction videos by wwgeb on YouTube helped the routing settings to eventually sink in. His multiple videos are highly recommended for their excellent production qualities and avoidance of irrelevant distractions.

The plan is to practice on the Sun today to see what can be done by a complete beginner before tomorrow's big day. I plan to capture a number of videos even if the Registax becomes more familiar over time. One the avi files are safely on my hard drive I can steadily increase my skill levels at stacking and "improving" them in Registax. Or not, if I mess up the avi files.

One could not ask for a more stable run of clear, sunny weather for the transit. The last Mercury transit was clouded over and the brand new "discount" re-chargeable batteries would not hold a charge! To this day I am uncertain whether I actually captured Mercury or merely a tiny sunspot. I had much more luck with the Venus transit.

Now I need to set up my old twin core AMD PC with iCap on board to capture some videos for some hands-on experience under the open sky. I can't reach my indoor PC with a USB cable and don't own a laptop. I just hope that older computer, and I, are up to the task!

Click on any image for an enlargement.

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7" f/12 R35 iStar refractor: Alignment, stepladders and Sun spotting.

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Once I had removed the slop from the focuser backplate it was easy to align the Cheshire on the center of the objective. The objective itself proved to be well aligned with the focuser.

Having mounted the OTA on the MkIV and fitted the full aperture solar filter I could see a single, large sunspot near the limb and suggestion of faculae in the area surrounding it. The umbra and penumbra were well seen on the sunspot.  I then stopped down the aperture to 6" and was rewarded with a sharper view. A 4" stop proved too small and actually seemed to soften the sunspot.

Trying to capture any of this with afocal 'snaps' is, again, proving frustratingly difficult. The image is so bright and uniform that the camera seeks out dust and dirt on the eyepiece in the absence of anything else on which to focus. I shall persevere in the hope of finding a setting which captures the visible details in time for the Mercury transit. My very first, Sony, compact digital camera took flawless astro images with auto settings. When that stopped working I bought this little Canon Ixus117 precisely for its short zoom and modest aperture as being most suitable for afocal, astro photography.

As can be seen in the image my new, folding, builder's stepladders have arrived. They were heavily discounted via an online dealer here in Denmark which finally swayed me to invest. I have been promising myself a pair of these steps for literally years after seeing a pair in a builder's merchants. These steps make perfect sense in providing incredible stability and modest height without having to teeter on narrow and uncomfortable, ladder rungs. Nor does the usual stepladder frame get in the way when loading telescopes.

I noticed instantly that I was standing on proper treads with decent width and depth which helps greatly with hands-free balance. The step's relatively gentle slopes are ideal for climbing with a large and heavy OTA in one's arms. The sheer size of these steps provides a large and steady footprint with a generous top platform about a 94cm or 29" high. This height provides me with the ability to look down on top of the horizontal OTA and MkIV mounting to make adjustments, tighten the clamping rings and fit a solar filter or aperture stop. 

My first half decent image of the Sun by afocal photography with the 7" stopped down to 6".[f14.4 =f/19.4 R35 equivalent.] Slight zooming seemed to help the camera find the correct focus. Remember that this image was obtained simply by holding the compact camera up to the eyepiece with a plastic, detergent bottle top, collar/adapter to center the Ixus 117 camera lens [nose] on the eyepiece without its rubber eye-shield fitted. [26mm Meade 4000.] I quite pleased with this image after struggling to capture anything at all! The camera registered 1/250 @ f/5.6. Image downsized from 3000x3000 pixels to 1000x1000 in PhotoFiltre with slightly increased contrast, reduced gamma but no sharpening. The Sun was at 48 degrees altitude above the roof of the house.

Indoor stepladders have proved lethal out of doors and I have toppled several times over the years! Finally, I have access, stability and safety to reach my telescopes on their tall pier without compromise. The steps will also be ideal for reaching the eyepiece of my 10" f/8 should I ever finish it. Now I have a further incentive to do so without worrying about ladder safety in the dark.

This type of low stepladder is used by the owners of some very expensive APO telescopes on an astro forum I frequent. If they are good enough for mounting telescopes costing many tens of thousands then they are probably good enough for little old me and my more modest, optical creations.The stepladder may even prove useful as variable height seat for refractor observation with a simple cushion for extra comfort.

I left the telescope drive running all day and was amused to see it pointing down at the ground in the west after dinner as it followed the sun well below the horizon. I went out again at 10pm to have a look at Jupiter. Seeing was softer than  ever in the arm and windy conditions. I tried various powers but only the lowest I tried 110x showed much detail in the belts. It wasn't a case of occasional sharpness but of regular loss of all detail. Yet again a tiny moon exited the limb and put distance between itself and the planet.

Towards the end I had a look around with the 32mm and 26mm eyepieces. The sky is never really dark at 55N at this time of year until well after 11pm. Even as I finished tidying up at nearly 11.30pm the dimmer stars were only beginning to show themselves. I am becoming quite at ease with the large instrument now. Even bringing the 'nose' down to remove the solar filter and refit the plywood storage plug. Having the instrument raised and leveled on the trailer jockey wheels gives it the extra height I need for sitting comfortable at the eyepiece when observing Jupiter at around 40 degrees. The new steps were handy for loosening the upper ring's clamping screw and tightening the clutches on the wormwheels before bringing down the OTA. Tipping it up slightly and allowing it to slide through the open rings is a comfortable way of handling the long and heavy tube.

Click on any image for an enlargement. 

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7" f/12 R35 iStar refractor: Jupiter 4/5/2016

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I spent some time on the refractor today. Starting with the refitting of the trailer wheels to get back the necessary height for the straight tubed OTA.  I also worked on the Vixen focuser to remove the last bit of shake when the focuser was rotated in the back plate. This required a thicker, plastic packing ring to take up the former slack. I wanted to line the inside of the focuser compression ring with felt to reduce friction but had none. Then it occurred to me that non-woven, disposable cleaning cloths have a very similar consistency. I now have the focuser firmly mounted and collimatable via stiff compression springs and the long retaining bolts inside the backplate.

The problem with my Orion Cheshire eyepiece is that its body is considerably undersized. So it rattles in all of the 2-1.25" adapters I own.[3] Unfortunately the rattle is too much for accuracy even with a compression ring type adapter. Yet the gap is too small for tape to be used as packing. The whole point of a Cheshire eyepiece is accurate optical alignment. Yet it feels as if I am using a length of string to measure alignment precisely. A collet style compression adapter would help but it has occurred to me that I could add further radial screws to the single one usually provided. A single screw will push the Cheshire off-axis but tilt remains an unknown. 

In fact I have yet to properly collimate the iStar to a high standard thanks to a number of factors. Not least having two OTAs to work on as I developed the folded form alongside the classical straight tube model. The former focuser slop has been one long hurdle but the sheer size of the OTA makes adjustment to the push-pull objective cell a time consuming business. Until now, I have been relying on the f/12 character of the lens to relax my demands on its perfect alignment. If I were to collimate the lens and focuser on the workbench I am still unsure if it would retain alignment after being lifted bodily onto the mount. Its great size and weight preclude gentle handling! Then it has to be taken down again at the end of the observing session and stored on its nose. [Again and again, over time.] One of the reasons for the desirability of an observatory is not having to remove the telescope from its mounting. Which should leave the optics free of mechanical shock. The answer, for the moment, is to repeatedly check the alignment once I feel the Cheshire can be trusted.

Once again I left the refractor out for several hours before I started observing Jupiter just after 10pm. At the lowest power of 68x, with the 32mm while searching for Jupiter without a finder, I could see promising detail in the belts. Increasing power through the usual steps ended with a rotation through the powers available. 220x with the 9.7mm was slightly too much tonight so I settled on 178x with the 12mm. Detail was absent due to thermally agitated seeing but I wanted to practice just staring at the planet in the hope of a brief clarity. There was none to be had tonight. I stopped the aperture down to 150mm and this seemed to help. I also tried the 'Fringe Killer' and noticed fleeting detail in the blank areas of the planet. This filter brought no greater detail in the belts and produced strong yellow cast and considerable dimming. Though the eye eventually forgets about the yellowing. Just as it does when wearing yellow safety glasses.

There was no sign of the GRS or any moon shadows this evening. Though I sensed texture in the belts it always evaded resolution. The limb seemed to be boiling gently but lowering the power to 144x did not help in seeing any greater detail. It just made the planet smaller which required more concentration. It's odd how low were the powers I used with my 6" f/8 Celestron refractor. I rarely pushed that over 120x even with the Baader 'Fringe Killer.' I used to amuse myself by seeing how low a power I could use and still see the Cassini Division on Saturn. It was still possible below 50x but such was the strain that it felt as if my eyeball was being sucked out by the eyepiece! The higher powers of the iStar have me spoilt. Or perhaps they are making me lazy?

The roof of my home had been basking in bright sunshine all day as the air temperature reached 60F. The roof lay directly below Jupiter but moving the pier would not have helped. Jupiter has moved too far west and I would need to drag the entire instrument down the drive past the house. This would have exposed me to the wash of poorly designed headlights of passing traffic. It's amazing what car manufacturers can get away with for the sake of styling, isn't it? Remember when headlights were round and cast a 'proper' beam without lighting up everything else in the entire area?

Out of focus views on a bright star was the usual vivid "bonfire" of rapidly moving colours. The Ronchi eyepiece merely confirmed the bad seeing conditions. After an hour and a quarter of struggling with the poor 'seeing' I packed up.

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7" f/12 R35 iStar refractor: Jupiter. 3/5/2016

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I made no effort to bring out the telescope as I had no idea how the forecast would turn out. It had been a pleasant and sunny afternoon as I worked on the folded OTA. At 10pm the sky was completely clear and it was calm at 42F. The long tube refractor was still assembled in the shed so I heaved it up onto the mounting. I had already fixed a slim Orion[UK] ring to the OTA to mark the balance point. This proved very handy as it gave me something solid to hook over the open, lower ring on the MkIV mounting. Then all I had to do was close both the hinged rings and screw them up tight.

There is an absolute magic about swinging a big, long refractor onto a target. The moment arm of the heavy tube and its ponderous length give a great sense of purpose in the classical sense. I have made no effort to smarten up the galvanized steel tube and bare alloy components. They have a ring of truth about them from an earlier age. No glossy white paintwork or vividly coloured anodizing are desired nor required. They would require I worried about cosmetic issues instead of getting on with the job of observing. Dragging a long and heavy instrument out of "busy" storage and onto a high mounting is not a delicate task at my age. The rings aren't even lined with the traditional felt but are bare laminated birch plywood. This instrument deserves and ought to be in an observatory but must be used out of doors with all its limitations of weight and lifting and carrying.
 
Centering Jupiter at 42 degrees high in the 32mm showed a small but sharp image with three moons. It looked quite promising so I brought out the heavy power supply and connected the drive cables to the box. The extension cable on its drum was unwound and brought out to the mounting. A 50-year old indicator lamp lit up and began to slowly pulse in time with the frequency of the VFO. 

Tightening the clutch on the polar axis wormwheel set it to follow Jupiter for the next hour and a half. The eyepiece in the 2" start diagonal was quite low as I had previously removed the trailer jockey wheels to better suit the [much shorter] folded OTA. So I brought out a folding wooden chair, settled down and rested an elbow on the trailer in perfect comfort.

I started working my way up through my mixed collection of secondhand Meade 4000s. Each shorter lens produced a larger but softer image with obvious thermal agitation on the planet's limb. I stopped at 10mm [actually 9.7mm] for a nominal 216x but an actual 222x. [If it matters] The image was now too soft and I stepped back to the 15mm and 12.4mm. Alternating between the two as my eye sought detail showed yet another tiny moon emerging from the right limb. As usual, I swapped to the 2x Barlow to obtain different powers with longer eps but this brought no obvious improvement.

Star diagonals make images the right way up but left to right reversed. My fuzzy memory can never remember which belt the GRS should appear in depending on various optical conveniences on its way to my eye. Just rotating the focuser with a star diagonal fitted will cheerfully rotate the planet to suit personal taste. I prefer my Jovian belts horizontal. A reflector will show a different view to a refractor. In this case the GRS was in the upper belt according to my rotated view.

I could not tell whether the tiny, emerging moon had been in front of behind Jupiter's stripey jumper. Then a small, black dot appeared projected in front of the planet but on the opposite limb. Both were directly in line with the lower, dark belt. The tan coloured GRS popped in and out of view with occasional glimpses of a whiteness nearby. The belts looked 'rough' at times but such views were only briefly seen.

Despite the relatively poor seeing it was better luck than I had been having. So I persevered as Jupiter slowly began to sag towards the chimney and then the ridge of our roof. Had I the wheels fitted I could have dragged the entire instrument on its massive pier to a better spot, but it wasn't to be tonight. 

Jupiter surprised me by its rapid movements. The GRS moved quite a way from the planet's meridian towards the limb in only one hour. The tiny, bright moon quickly broke free of the limb and was soon putting considerable distance between itself and the planet. The shadow followed suit and was heading toward the center line of the planet.

Every view of the planets should be treated as practice in seeing the impossible against impossible odds. The seeing can clear in brief moments but cannot be predicted. So the eye has to learn to cope with these difficulties and train itself to capture the sharp moments. As it builds up an image distinct from the 'noise' of thermal agitation and variable softness.

I added a 6" and then the 4" stop to the dewshield and found some benefit with the 6". The four inch was just too small. Again the violet haze was more noticeable coming back up from the smaller apertures. It was a difficult choice but I actually preferred the 6" in tonight's seeing. This choice would probably change if the seeing was better or worse.

I removed the 2" dielectric star diagonal and fitted the little, no-name 1.25". No discernible difference that I could see. Just before I gave up for the night I brought out the straight focus extensions. The odd thing was that these seemed to make things worse rather than better. I had already given the interiors a good coat of matt black paint since they were delivered black anodized but all shiny inside!

I rather liked the long tubed refractor for aesthetic reasons. It is far more impressive in scale compared with the rather "techy" folded form. At over 2.2 meters tall when standing on its shorter dewshield it is impossible to reach the focuser to plug it without something to stand on. Once mounted it soars high into the air like a "proper" telescope. It's just a shame it is such a struggle to get it up there! Then having to move it around the garden to find some sky clear of trees, hot roofs and tall hedges! If I built a raised platform 8' high I'd have most of the sky to look at but then I worry about vibration and shelter. It's not easy being an amateur astronomer in the real world! ;-)

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7" f/12 R35 folded iStar refractor. Quick-fit OTA.

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I needed something more substantial to support the folded OTA on the 60cm, 24" saddle of the MkIV Fullerscopes mounting. The present 18mm, 3/4" birch, plywood battens flexed too much. Which tended to amplify any vibrations from focusing or holding a camera to the eyepiece for afocal photography. 

Amongst my collection of "scrap" metals "likely to prove useful one day" I found a plate of 10mm aluminium alloy. There was just enough material to make two new crossbars about 75mm, 3" wide. Providing a far stiffer arrangement than the rather narrow 3/4" plywood battens. The 10mm thickness also saves an extra 8mm, 3/8"" of overhang beyond the saddle compared with the plywood battens. Every little helps where OTA overhang is concerned as it requires less counter-weighting ensuring less moment. Remember that Moment = Mass x Distance from the fulcrum. Many mountings are already, completely inadequate to the task of supporting a large refractor!

 Next I needed a new way to fit and lock the OTA onto these crossbars without the use of tools. The rotating, slotted, plywood crossbars had proved awkward when fitting the OTA onto the saddle. Moreover the wing nuts were too small and hurt my hands when I tightened enough to stop the OTA slipping irrevocably downwards on the crossbars when pointing upwards. Adding through bolts and wingnuts through drilled holes when mounting a heavy OTA is a disaster waiting to happen!

The answer lay in some larger coach screws, some coil springs and much larger wing nuts. The rusty spacer is just something I found handy to illustrate the depth of spacer required. The screw holes will not be offset as they appear in the image.

Imagine there are short slots cut in the 10mm aluminium, crossbars wide enough to clear the springs and square shanks under the coach screw heads. The telescope framework will have four holes drilled to match the rest position of the OTA when the coach screws are safely housed in the bottoms of the slots. 

The underside holes in the framework tubing will be drilled to clear the springs and square screw shanks. The upper holes will just clear the round shanks of the screws. The springs will butt against the insides of the tubes. So that the pressure of the coil springs will push the large screw heads downwards. Thus the screw heads will always safely clear the alloy crossbars to allow the screws to effortlessly enter the location slots provided.

The image shows the 12" x 1/2" x 1.5" alloy crossbars in place on the saddle.[300 x 12.5 x 38mm] The crossbars have to be marked, drilled and slotted for the OTA's projecting [quick release] fixing screws.

A [suitable] spacer above the tubes will allow the wingnuts to clear the Porsa tubing flange. The wing nuts will tension the screws when desired so that, once safely located in the slots in the crossbars, the coach screws can be tightened. Which will pull the underside of the large heads of the coach screws upwards against the underside of  the sturdy alloy crossbar. The coach screws thus act as locating pins in the slots but also lock the OTA firmly into place onto the thick, alloy crossbars by the friction of compression. I have now found some 1/2" x 1.5" alloy bar and will use that for the crossbars.

Without the springs the coach screws have no longitudinal locatory force. So that the screws might rise enough for the heads to jam against the crossbar at an inopportune moment. The springs ensure there will always be clearance under the screw heads until the wing nuts are finally tightened. An equatorial mounting needs the OTA to be safely located and locked into position. Or it may slip out of the location slots under certain pointing angles.

The springs and coach screws in place on the bottom rails of the Porsa tubing, folded OTA are extended by just over 1/2 inch to the undersides of the screw heads.. I have yet to make, or find some spacers, to allow wing nuts to clear the tubing flanges. Next job is to slot the crossbars to clear the springs.

It has been raining all morning but has now brightened up. So I can saw the new crossbars and file everything smooth. Followed by the cutting of the location slots and drilling the crossbars to saddle fixing holes. Once the exact balance point is certain I can mark and drill the framework for the four coach screws to match the bottoms of the locating slots in the crossbars. Adding the crossbars to the saddle avoids having to carry them while attached to the OTA.

When I want to swap the folded OTA for the long tube, perhaps for solar work, I just undo the bolts holding the crossbars to the saddle. Then fix the hinged rings to hold the tubular OTA in place.

Click on any image for an enlargement.    

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7" f/12 R35 iStar straight tubed refractor: Testing-testing.

10pm[CET] 1st May 2016.

Having been disappointed, yet again by Jupiter's lack of clarity, I then checked the collimation with the Cheshire e.p. This confirmed it was really quite good with the bright, reflected spots overlapping closely.

The presence of two bright stars, one to the east and the other to the west, suggested I conduct some star tests. A very colourful experience that proved to be with violent thermal agitation! Almost as if a vivid stream of colour was rushing past the multiple fine rings and badly frayed edges each side of focus. It was difficult to be certain that the brightly coloured mess actually had a focal point where the star contracted to an intense, spangled, constantly moving, intense yellowish dot. The green and magenta were certainly pretty but it was no surprise that Jupiter was another disappointment.

I brought out the Neumann Ronchi test eyepiece for the very first time and was delighted [at first] to see dead straight lines outside focus. The problems started as I neared focus and the lines rapidly spread out [as expected]. The outer lines began to bend sharply around the edges of the lens as if testing a steep parabola at the center of curvature. Again the vivid colours showed that it was an achromat and not a mirror. Inside focus the curvature was absent and the lines remained straight but greatly expanded as expected. Nearer focus there was a single black line across the center and two, multi-hued outer lines.

Not ideal conditions for testing due to the strong thermal currents. The sun had shone brightly all day from a clear blue sky. Though thin cloud had passed over in the early evening it had gone by 10pm. Could the OTA have retained some heat despite falling into shadow by 5pm?Five hours to cool 10F? I doubt it. Should I install a fan and ventilation port to help cool the thin, steel tube? Metal is a very good conductor so the tube had probably cooled well enough in the 10F drop over several hours.  The lens elements are quite massive but surely four to five hours of exposure to the cooling air is enough to follow those few degrees?

I think I have proved to my own satisfaction that the folded design does not detract from whatever the lens can show in good seeing conditions. Each OTA needs a different height of pier and very different fixing methods to the same mounting saddle. Though I had no great difficulty lifting the long and heavy OTA back down at 11.30pm, the lift back up next time is not something to which I look forwards. So I shall rebuild the folded OTA and seriously reinforce the [temporary] fixing crossbars to reduce flexure. I could even use a keyhole bayonet fitting to the saddle crossbars to reduce the present balancing act on the beer crates and stepladders.

The folded OTA is rather bulky and certainly no lightweight, but promises easier handling. Particularly as the objective lens can be fitted via its bayonet rather than being part of the overall weight of the OTA. Overcoming the psychological hurdle to going out to observe always requires the least potential effort ahead. At least I [think I] have proved that the straight tube is not a night and day improvement over a folded optical path.  Further star testing and the Ronchi test EP will follow when conditions improve. Meanwhile I shall continue to practice my solar photography.       

Click on any image for an enlargement.

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7" f/12 R35 iStar folded and straight refractor on the Sun.

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Sunday 1st May and bright sunshine in a cloudless sky as it reached 55F, 13C after an overnight frost. Time to test the new Baader full aperture filter using Astro-Solar foil.

 The Sun's disk with a 640x480  frame size camera setting through 32mm Meade 4000 ep full aperture 180mm Baader Astro-Solar foil filter.

The Sun resized from 3000x3000 on the Ixus 117 compact camera to 1000x1000 in PhotoFiltre. [32mm Meade 4000 S. Plossl ep. This image was taken with the refractor returned to a long straight tube to see if it helped to improve contrast over the folded form. Not visibly thanks goodness! Is that even a good thing? Any slight improvement in sharpness was probably due to the increased altitude of the Sun in the sky by the time I had finished the conversion. There is a very narrow deep violet rim if you enlarge the image by clicking on it. This fringe is completely invisible visually.

The short zoom, compact camera doesn't seem to be behaving as reliably it does on the Moon. There is no sense of a bright uniform disk against a black background in the viewfinder screen. Even the brightness varies across the disk. Giving it almost a pearl-like effect. I keep getting images of dirt and dust instead of the camera focusing on the Sun. This has never occurred before today. I have tried Auto and a whole range of program settings without much success.

There are quite a number of sunspots but they are all rather small. Stopping down the 7" lens to 6" and then 4" aperture seem not to have much effect other than loss of light and easier focusing requirement.

At focus there was no visible limb fringing at any aperture. Though the limb was 'boiling' for most of the morning, in the folded refractor form, it seems to have settled down now. This is despite the roof of the house being below the Sun in the sky from early afternoon. A gentle, easterly wind may be helping to carry the thermal currents away. I have just had to reverse the OTA to the other side of the pier as the sun reached further west. The 7" worm drives on the old mounting seem to be able to cope provided the OTA is well balanced. The OTA balance weight is very helpful to save trying to push the heavy OTA through the loosened rings.

The image shows the straight-tubed 7" f/12 iStar refractor following the sun on the MkIV Fullerscopes mounting on its massive, welded steel pier. The instrument's sheer size is difficult to judge even knowing the main tube is 8" 20cm in diameter and 2m, or over 6 feet long, without the dewshield. The pier flange is 5' [150cm] from the ground without the wheels fitted. The center of the saddle is 2m or 6' 6" above the ground. Even so it it requires a low chair to use the star diagonal as the telescope points higher. I have no great desire to add more mass to the focuser just to lift the telescope higher. So use the trailer jockey wheels when the OTA is in the long, straight tube form.

Lifting the OTA into place ideally requires a short set of builder's steps. Wide rungs are necessary for stability but only three, or possibly four, steps needed in all. The tall folding ladders shown with the telescope are quite stable laterally. But far too steep to provide the stability needed to climb effortlessly to the correct height when carrying a heavy OTA. I have had to rapidly step backwards onto the ground when the ladders have tipped towards me while I was holding the OTA in my arms! These ladders really need several extra pairs of hands to hold on at the same time! They also get in the way during fitting the OTA to the mounting. Only the permanently fitted, short dewshield is in place here. There being absolutely no need for the full dewshield on a warm and sunny day like today.

The telescope was left outside to cool until 10pm when Jupiter was close to the meridian. [South] As the sun had never fallen directly on the tube I imagined it had never really warmed up beyond the 13C, 53F maximum air temperature. The full aperture, solar foil filter should have protected the glass from any heat build up. The OTA certainly felt cool to the touch when I went out to find the temperature had dropped to 42F. Brilliant Jupiter had reached about 42 degrees local altitude. Unfortunately there was little to be seen beyond two dark belts and a hint of a third. No power I tried up to and over 250x made the planet any clearer. As usual, I tried the Yellow No8 and then the Fringe Killer filters but they made no visible difference to clarity. There was no finer detail, at all, to be seen.

Click on any image for an enlargement.

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