27th April 2019 Just don't mention inverted parking!!

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Saturday 64/61F The Altazimuth figures on the AWR IH2 screen were completely wrong again when I powered up the system. So I changed to Equatorial coordinates and Synced on the easterly horizon. Changing back to Altazimuth coordinates now found them to be correct despite being warned of yet another "Perimeter Exceeded." I pressed SETPK in the hope that the Home button would send it back to the correct parking position later on.

Much too cloudy today for any serious solar observation let alone imaging. So I played with a variety of GPCs [and without] in the binoviewer. 

For low power, white light views of the whole disk then the 44mm Meade 4000s are very pleasing without a GPC in the 2160mm focal length, 7" refractor. When two streams of cloud are crossing the field of view at 45° to each other, this is an almost magical set-up. Rather like a camera obscura. I had to remove the 80mm x 2" extension tube to reach inward focus without a GPC.

Changing to 32mm eyepieces increased the power to about 70x. This is far more impressive as a closer view. With a much larger disk to admire while still leaving a useful annulus of sky. Though now it requires that I roll my eyes to study the entire limb for sunspots. Or view half a disk at a time. So not so relaxing as the 44mms despite the much smaller field of view than the 32mms.

Adding the 2x WO Barlow nose to the binoviewers provides a huge solar disk but now needs the telescope to be driven around. To see the whole of the solar disk in small sections.

BTW: The 100mm/4" friction wheel and 7" bicycle crank continue to give excellent service in effortless dome rotation. A day's enjoyment of the sun requires quite regular cranking to cover 90 degrees of sky. The industrial PU trolley wheel works well against the bare underside of the birch plywood base ring. The secret ingredient being the 5kg counterweight on the far end of the compensating see-saw. The weight rises and falls to match variations in ring height. Though I am completely unaware of any slight vertical movements of the crank bearing during operation.

Finally it was time to pack up. So I hit "Home" on the IH2 paddle to park the telescope. Being an eternal optimist I was fully expecting facing east, weights down to the north, as requested. Then I watched bemused as the telescope decided it was much more fun to face east but with the weights right up to the south. I kid you not! I had to vacate my computer seat as the telescopes swung by in exceeeedingly slow motion.

Being of an experimental nature I decided to let it have its head. Just to see how many turns of declination motor cable it could manage to wrap around the mounting before something broke. [I'm joking of course.] The thin white lead is i the image for the overhead, LED work light but is quite slack so in no danger.

Quite unbelievably the telescopes finally stopped precisely at the Eastern pointing position but "upside down." I was told I had crossed the meridian several times on its journey with a loud bleep and curt message.

Not to mention several excursions into "Perimeter Exceeded" land. I still haven't a clue as to the whys or wherefores of this message. I hope you appreciate the lengths heights I had to get to just to capture the moment for posterity. It involved an empty beer crate and stretching upwards with the camera over the yawning gap in the floor just to get it all in!

I seem to have obtained a nice view of the free blacking of the birch plywood dome interior as the winter mould gains a nice suntan. If I wait long enough for the mould to take over I shouldn't ever need a paintbrush! The same can't be said for the rusty counterweights. I have a tin of smooth, white Hammerite just waiting but need the right conditions to proceed. Preferably with the weights down where I can actually reach them without needing a stepladder!

Eventually I was able to sit down to drive the telescopes all the way back again on the paddle. The AWR IH2 handset ignored all attempts at a "Flip." PERIMETER EXCEEDED!!!" Perhaps I should get an outboard motor just for speeding up the parking? Or I could fix a clamp on the paddle buttons to save pressing them for several minutes on end? I could easily get RSI at this rate and that would never do! 

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25th April 2019 Solar & Goto.

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An odd start with the telescope 'target' overlaid on the eastern horizon in C-Du-C. To match the supposed parking place in AWR. Hopefully a positive sign.

First attempt to slew to the sun resulted in a slew to the north east! The sun was high in the south east! Crap! So I had to abandon the slew and manually drive the telescope via the paddle after sending it almost Home to the parking position to save time.

I then went into the AWR Factory Menu [Info> Reboot+M] and changed Max-Dec to 88 degrees. This is supposed to stop the mounting trying to go the long way around over the pole.  

Once centred on the sun there was nothing visible on the disk in WL. In H-a I could see nothing either. Not even a prom when Gong Ha showed lots all along the eastern limb. Later examination via the ZWO showed them well and I captured a couple of videos.

Before a break for lunch I was trying to focus on fine surface detail in white light with the ZWO camera. The area of detail is highly dependent on how much of the solar disk appears in the field of view. A brightness or contrast effect.

The DC motor focusing works well enough but I have substituted the stiff O-ring with rubber bands. Ideally I need a much thinner and weaker O-ring of about the same diameter Which could [hopefully] slip on the motor pulley when I need to manually coarse focus by means of the adjustment knobs. The focuser needs only a little torque on the fine focus knob to turn reliably.

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23rd April 2019 Gales!

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Yet another clear, bright day but spoilt by easterly gales with gusts up to 21m/s [45mph]. With the early sun in the east there is a potential danger of blowing up the dome if the shutters are wide open to the wind. Yesterday the dome rotated on its own when a sudden gust caught the open shutters at 90°.  The dome cannot lift because of the hold down disks beside each, of eight, supporting rollers. Why take a chance with the wind when the sun is bereft of interest at the moment?

I shall work on the mounting and tracking instead. I don't need the dome open to slew between Polaris and the parking position. Further fine tuning of the balance won't do any harm and will keep me out of mischief.

In fact my visit to the dome was very short lived. I turned the firmly closed shutters into the wind and retreated from the racket the wind was making. Mostly caused by the rubber skirt flapping hard against the building and the plastic upstand.

24th  Now overcast and still windy but reduced from yesterday's gales. The promised overnight rain must have missed us as we head into another 9/10 drought warning. With brown dust clouds hanging over the fields.

Now it is more comfortable in the dome I can hopefully return to sorting out the Goto slew overshoots. Hours passed this morning without Goto progress until I discovered that C-Du_C had not updated the time since at least the Summer time change. Ticking "Use System Time" and restarting the laptop and AWR solved that problem. Later I reached the parking position from a paddle driven centring and Sync on the Sun. Is this the beginning of the end for my endless Goto problems? Who knows? 

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Balancing a GEM in all planes.

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Here the telescopes have overshot the parking position. The weights should be low and in line with the mounting. The telescope tubes should be horizontal.

While forcing a deliberate Meridian Flip the motors stalled with the OTAs near the vertical. So I loosened all 6 clutch screws and rebalanced the mounting and OTAs.

The considerable torque required to drive and resist unwanted movement of the OTAs demands stiff clutches. The telescopes must always be motor driven around the sky and never pushed independently of the motors. Otherwise the precise count of motor rotations would be lost. Along with the telescopes' precise pointing position on the sky.

The Beacon Hill wormwheel sets each had only one screw pushing a small plastic pad onto their respective axes shafts. This was found to be inadequate with such long and heavy telescopes. So I added two more screws and pads at 120° intervals around the wheel bosses. Loosening all the screws is enough to allow accurate balancing but is not perfectly free of friction. The bosses themselves add their own friction along with the large, flange mounted, self aligning, ball bearings supporting the shafts.

It took some time and effort to achieve balance in all positions. This was mainly due to the offset, 6" H-alpha telescope fixed to the side of the saddle via tube rings. I chose this position to avoid needing more counterweighting on the Declination shaft. As would have occured if I had mounted the 6" onto the 7" tube. The weight of the 6" would also have been added to the load on the 7" tube rings.

I have ringed the fixed, offset weights which counterbalance the 6" H-alpha telescope in the image above. The smaller, brass weights on the sliding rail fixed to the saddle are used to balance heavy items on the focuser end. The great distance from the focuser to the axes on larger telescopes can easily produce dramatic changes in balance. The solar prism and binoviewers add nearly a kilo each. A long and heavy telescope is not easy to control when it suddenly wants to swing nose down!

A single telescope would not suffer from major offset forces. [Except for a heavy finder, if any.] My own system needed considerable reduction in the moment [mass x distance from the pivot] of the offset counterweights. I hadn't been able to judge this when balancing with the telescope tubes horizontal. Fortunately I have a selection of small, barbell weights from an Aldi special offer in 1/2, 1.25 and 1.5kg. Or roughly 1, 2 and 3lbs.

This shift in offset balance had to be managed without the main counterweights becoming dominant. The critical position was with the OTAs vertical. Only in this position do the offset forces display themselves and allow adjustment.

It's no use just balancing the OTAs when they are horizontal. Such large and heavy OTAs have to be balanced in all possible positions. So that the OTA's have no bias in any direction. It is often possible to sense a desire for the OTAs to continue moving on in a particular direction even when they stop when released. It takes considerable patience to achieve full neutrality.

This exercise must, of course, include any heavy accessories. A slight eastern bias is considered desirable to take up any backlash in the drives. The wormwheel teeth can then remain in continuous contact instead of rocking between teeth. The usual expectation is that drives will push the telescopes gently but constantly uphill towards the west to "follow the sky." Any imbalance would inevitably throw such ideal drives completely awry!

Click on any image for an enlargement.

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ASCOM[AWR] Cartes-Du-Ciel GOTO woes.

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My GOTO slews within C-Du-C, IH2 Home and Park are all complete and utter nonsense. No matter how often I Sync on the Parking position, or on the Sun or Moon, the system cannot move reliably to another object. I thought the Local Sidereal Time might be off so I used online calculators to confirm. No problem there. Accurate to within a couple of seconds of the reading on the IH2.

I always park the telescopes horizontal and pointing east, weights down. Every single time I have to drive the telescopes there using either paddle on closing down. Using Home will never find the parking position. Perhaps once during my entire use of the system. 

Starting each observing session I  take LST from the handset then add 6 hours and enter the Sync coordinates on the parking position. Then add Dec as 0° 0' 0". I then repeat the same operation in C-Du-C. Syncing on an object on the eastern horizon before attempting any telescope slews. I check the bottom line in C-Du_C for the correct Altazimuth coordinates and RA Dec match.

Having checked the main tube of the 7" is truly horizontal with a builder's level I then press SETPK. [Set park] What could possibly go wrong? Remember that the telescope hasn't yet moved so you'd think I could press SETPK again just to confirm. But no! Not calibrated! It is supposed to have remembered the parking position from last time! So I calibrate again and then press SETPK. Completed.

Only then can I click on the Sun in C-Du-C and "Slew to." If it ever arrived on the Sun I would hold a neighbourhood party to celebrate! It always overshoots by miles and ends up at completely the wrong altitude. So I drive the telescope back to point at the sun using either paddle and then Sync on the sun in C-Du-C. Knowing the coordinates I can now Sync the Sun on the AWR IH2 handset. Just in case. Now try pressing Home to have it park? Always garbage/random positioning!

I have repeatedly checked the polar altitude of my big mounting. Most lately with a 0.1° digital clinometer on my 2" polar shaft. I checked my local north pointing angle at 3° E positive declination or magnetic variation. The pole Star is not always visible due to a large tree right behind the observatory. [Season and leaves permitting.]

So I lay a 2m long builders straight edge against each base fork tine in turn. With the free end resting on the dome's roller ring to confirm it is all north pointing. While being careful to avoid any iron in the vicinity I [gently] adjust the azimuth with a 4' long scaffolding pole. The mounting is massively heavy!

I just rechecked the easterly horizontal position, weights down, Synced on the IH2 and was greeted with "Perimeter Exceeded!"  So now I can't even Sync on the parking position! So I go through all the Syncing rigmarole again and it accepts it. I hit SETPK and it accepts that too. But for how long?

The madness goes on: Having just confirmed that both AWR and C-Du-C were showing parked on the numbers I sent the telescopes to Polaris. It seems Polaris is now 20° west of its last known position! Should I confirm this change with the astronomical authorities and claim my Nobel Prize for Physics? Or should that be a prize in astrology?

Having moved the telescopes to the traditional position over the polar axis and pointing at the Pole [via the paddle] I pressed Home for park. The polar axis started turning and resolutely headed east. The 7" objective is now staring down at the floor of the observatory towards the north east!

That is only two mounting movements and both slews were to completely the wrong target! The Polar Axis need not have turned AT ALL in both cases. So it was just a simple Declination slew. When I closed down the Altazimuth parking readings were shown on the IH2 screen. These too were complete and utter garbage! Now, where do I enter "Garbage" for the next target!

Overcoming these positioning problems is wide open to multiple false starts. ASCOM[AWR] or AWR or C-Du-C?  Where do I start? My fuzzy logic suggests I isolate the basic AWR system first to see how it copes. I don't have an onboard object list. So need to remind myself how to go about simple Gotos to manually entered coordinates.

The planetarium, computer control is an add-on feature via the USB/Serial cable. If it's not connected then it can't do any harm. An air gap will leave AWR's system to do its own thing. I can get suitable coordinates from the planetarium screen in splendid isolation.

I tried changing the time settings in C/Du/C.  This helped. I believe the main problem was disagreement between AWR and C-Du-C over the LST. Local Sidereal Time.

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21st April 2019 H-alpha experiments.

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I had a nasty moment when the binoviewers suddenly swung downwards along with the Lacerta prism. Fortunately they remained attached. Or they could easily both have fallen down through the ladder hatch! It was not the prism's fault [at all] but the cheap 2" x 80mm [Taiwanese] extension into which the big prism fits into.

There was a normal, brass compression band in the extension but only one, small thumbscrew. So I used the 3-jaw chuck in the lathe to mark the extension 120° apart. Then drilled and tapped two new 3.5mm holes, M4, for two more thumbscrews to compress the band. I borrowed large-headed thumbscrews from other compression fittings in my growing collection. It won't dare move now! Never [ever] trust a single thumbscrew!

The images show experiments with star diagonals to shorten the ridiculously long H-alpha, filter chain. A 2" and a 1.25" elbow were tried. Both set-ups achieved focus with the camera fitted as shown. Though various Barlows/GPCs were required.

Sharpness was lost compared with "straight through." Though the sky was showing thin cloud at the time so I should really reserve judgment. Increasing the magnification via Barlows also contributed to increased softness of the image. This also exaggerated any wind movement of course.

I am playing with ImPGG to see how it works. This is my first attempt at capturing and processing prominences. Overdone, so noisy and grainy.

The image on the right is using Registax and overdoing Wavelets to overemphasize surface features.

Click on any image for an enlargement.

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19th April 2019 Last rasher of AR 2738

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Friday 64-65F, bright but rather windy. AR2738 is now very close to the limb. Followed by the two small spots.

The first two are white light images after processing in Registax and PhotoFiltre. Capturing the video at 60fps and then pushing it through the software takes only a couple of minutes. So an astronomical event can be live on the internet within only a few minutes. I have to reduce my images in file size for the blog and smaller again for the forums. Otherwise it would be even quicker.



For some reason it is traditional to post images in marmalade orange. Not lemon yellow as here! I'm still trying to get PhotoFiltre to cooperate.

I took the opportunity to push the yellow image too hard in Registax Wavelets and FF contrast to bring out all possible detail. The effect is very artificial but still interesting. I am seeing exquisite surface detail on the 4K laptop screen but it is always lost in processing.

The next three images on the right are captured in H-alpha.

AR2738 exits [slowly] stage right on a burning funeral pyre of prominences. I should have respected correct orientation of these two H-a images but never thought about it at the time. It is only a matter of rotating the camera in the telescope fitting. Now too late because I have already labelled them.

It was not a great spot but it certainly earned its keep while on the stage.

There are rumours going around that the present/future Solar Minimum will be deep and spotless. I like to think that every prom on the arrival limb is a potential spot. While my while light images aren't too bad I'm still lacking definition in H-alpha.

All the detailed imagery on the forums seems to be coming from Daystar Quarks. I know I can capture much of the white light detail with my new ZWO120 but the H-a results are patchy and lack the surface swirls of better images. I do need a focuser for the H-alpha train but there's more to it than that. Now it has been suggested that I investigate ImPGG software.

Click on any image for an enlargement.

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April 18th 2019 Focuser motor & AR2738

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I turned a brass V-pulley for the "Skywatcher" DC focuser motor. The motor can easily cope with lifting the weight of the big solar prism and binoviewer but does so rather slowly even on fastest speed. It does just the same when lowering all that weight.

I don't like the curly "telephone" cable and will be looking for a much longer straight one. Just found a 2m long white one in my vast cable collection. Being able to fine focus without touching the telescope is a revelation in fine detail. Which you would [probably] never achieve without considerable luck.

Thursday: 57/55F, clear and sunny.

10.20: AR2738 is heading for the limb at 3.00. Two small spots inboard of AR2738.

The large spot is getting very close to the limb and will soon be invisible as it travels onwards out of sight.

We must hope another spot arrives on the opposite limb. To replace it and hold interest for all the solar observers and imagers around the globe. A spot a day keeps the Minimum at bay.

I am very pleased with the surface detail I am capturing at the moment. The solar cells of granulation are just on the verge of individual clarity in the small spots image. Though I have to be careful not to overdo Wavelets in Registax. I have watched lots of YT tutorials but struggle to remember a lot of the detailed advice. Nor do I have access to Photoshop which many imagers use for its sophisticated "powers" to enhance the final images.

In H-alpha a patch of plage is visible where the smaller spots show in WL.

The seeing conditions deteriorated badly in the afternoon as the sun heated the house roof to my south. There may have been some thermal effects from the dome surface as well. Heat rising out of the observation slit disturbs the view. Rather like the background wavers when seen over a garden bonfire. Telescopes magnify so much that they are far more sensitive to variations of refractive index with the changing temperature of the air.

The 2" Lacerta Herschel prism's heatsink became too hot to touch today after hours of tracking the sun. Instrumental, internal thermal effects should not be ignored in image quality. I withdrew an H-alpha fitting one day to see swirling heat effects in the bright red beam. Should I consider a vent or a small fan to draw warm air out of my telescope tubes? I do have the option of painting the dome white to reflect more heat. Today the plywood panel were radiating heat inside the dome like a domestic heater. That can't be good for seeing conditions! Do I want to draw more attention to the dome? White will certainly make it far more visible. Though it is a race against time with the neighbour's rapid tree growth. Distant views of the dome will shortly become impossible as the trees come into leaf.

Even a modified [secondhand] PST etalon/filter system is not the world leader in H-alpha image quality. There are larger filters in increasingly expensive, solar "elbows." Then there is the Quark device which is popular in bringing out amazing surface texture at considerable cost. Not to mention the increasing use of full aperture, external, rejection filters on SCTs. These can bring much larger apertures into play with amazing image resolution but at ever increasing cost. The external filter has the advantage of removing a lot of heat before it enters the instrument. While I am using a smaller, internal D-ERF inside my battered, old, secondhand, 6" f/8 refractor on the grounds of cost.

 Click on any image for an enlargement.

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17th April 2019 solar AR2738

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Another long, sunny day.

1050 AR2738 moving inexorably towards the limb.

WL Just a hint of the lighter bridge left on the umbra.

The images show the full size image in Baader SC green.

With a resized monochrome image below.

These early images with light winds has captured even more of the cellular surface structure.



 Reprocessed in Registax: Resized to 800:

I still had everything set up for some lunar video captures later but the seeing had gone soft.

Click on any image for an enlargement.

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15th and 16th April: Imaging the moon and sun.

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First attempt at capturing Plato with the ZWO120. SharpCap, Registax and PhotoFiltre. Still daylight with the wind blowing straight through the slit. The telescope is unbalanced and hasn't even been collimated. The wind kept making the images move on the laptop screen.

I rushed the results through Registax then resized the final image in PhotoFiltre before dinner.

Note the tiny craters in Plato!

Similar image but captured after dinner. Now after dark, with the slit facing further south. So the gyrations during gusts were not quite so violent. 

Needless to say I am delighted with these early results.

Using the binoviewers with the 2x WO Barlow produced about 175x visually but seeing the minor craters in Plato were more wishful thinking than reality. Interestingly, I could easily see at least three craterlets on the 4K laptop screen in SharpCap.

Just imagine the images of Plato I could produce with the 10" F/8! I had no problem seeing Plato's craterlets through that. All it takes is to come up with a working design which is stiff enough without massive weight. Though I doubt the mounting could cope with three telescopes without added reinforcement. The long moment arm of all three instruments is working against me. With such long OTAs the addition or removal of an eyepiece, camera, diagonal, solar prism or binoviewers alters the balance drastically. I suppose I could make the 7" into an H-alpha telescope and get rid of the 6".

I spent an hour improving the balance and then captured some more videos of AR2738 in WL and H-a. My 500GB SSD is now full and I have had to keep removing old videos so make room for new! The daft SSD has loaded every single image and video that was put on the laptop from new!

With Google and Microsoft both providing cloud storage I wonder how long I need to keep these hard drives full. I really only need the latest videos to process at my leisure.

My white light image of AR2738 still shows a faint, offset, cross-shaped bridge. I have converted the apple green image [from the Baader SC filter] to mono to bring out this detail. I seem to have captured a hint of the cellular, surface structure too.

16th evening: I was going to go out and capture more lunar videos but the wind has really picked up again. It is blowing from the east. Just as it did yesterday evening when it buffeted the telescopes.

Wednesday: Another long and sunny day promised but with the easterly wind still a feature. With the early sun in the south-east it will make it rather draughty in the dome. It's is lucky I haven't had the big dewshield fitted on the 7" to catch the wind.

Click on any image for an enlargement.

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14/15th April 2019

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Sunday: I brought down the 7" OTA and removed the objective, tailpiece, handles, weight rail and Vixen focuser. Then shortened the main tube by 150mm/ 6". The FTF is about 30mm longer than the Vixen both at minimum length. The turned base ring adds another 20mm. So I added 50mm to the difference. This should allow me to reach focus with the 2" Lacerta prism and binoviewer. It is very easy to add 2" extenders but far more difficult to reach inward focus.

A slight worry is the great difference in weight between the two focusers. Weight at the tail end means moving the OTA up through the rings. There isn't an an awful lot of clearance now. So I'll just have to move the offset weights for the 6" H-alpha 'scope to the top of the 30" long saddle. I already had weights up there but moved them down to the focuser end. This was to balance the added weight of the offset 6" mounted, via tube rings, on the saddle.

After spending so much time on the backplate I changed my mind. I have decided to sandwich the original [saucepan] tailpiece with the focuser collar and base ring. This required I turn a shoulder on the custom base ring. Meanwhile I shall be looking for another saucepan with much less taper.

I put the laminated plywood internal rings back in the lathe and turned the outer surface to better match the saucepan's curve. Then I was able to make use of the original collimation springs in the shorter gap. I reconsidered the sandwich when I realised that I was merely duplicating the FTF rotation system. The custom base ring needs to be firmly anchored to the saucepan base. Then the FTF collar can do its thing.

Springs are probably a bad idea with such a heavy focuser on an equatorial mount. It would tend to sag around the optical axis in all positions. So I need to add push screws for locking the collimation as well. All this would be far better done on a straight-sided pan base.

I now have the 7" refractor in pieces just as the sky clears.  The Moon is high in the south, the sun has an interesting spot and my new camera is sitting uselessly on my computer desk.

Monday: I refitted the tapered tail end with the springs and large washers keeping the custom base ring rigidly in place. Then I dragged the bare tube upstairs to the observatory and fitted the objective back on. Then the big focuser was attached to the updated tailpiece.

I fitted the 7" and re-balanced the telescopes while duplicating the offset weights. Still a little extra care in balancing is required. I have moved the 7" main tube higher in the rings for more floor clearance as the sun climbs higher.

Finally I was able to find the sun and try the new focuser. It is an absolute delight to use after my struggles with the floppy/tight Vixen. No more sag and the focusing action is superb. It seems I overdid the shortening of the main tube when the WO Barlow is on the binoviewer nose. So I added a short 2" extension to bring the draw tube to half way.  Without the Barlow I should finally have low power binoviewing.

The bridge on AR2738 has moved towards one end of the spot. My first clear, visual view of super-granulation at 140x and 170x thanks to the binoviewers. The sun spot is spectacular!

A quick glance in H-alpha also showed the bridge against a large dark spot. With two large prominences visible.

13.30: Stopped for lunch. I shall be back out there with the ZWO camera and laptop this afternoon. Though I could see fine surface detail in both WL and H-a I seeemed unable to capture it.

Click on any image for an enlargement.

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14th April 2019 Of piers and spots and focusers and things.

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Sunday: For hours I tried repeatedly to get Registax on my PC to open my solar videos from the SSD but it refused. I had to move a video from the SSD to the PC desktop before it finally opened. 

The results of my labours were strange indeed! AR2738 had the distinct appearance of having been burnt by a magnifying glass focusing the sun's image on paper. It was still glowing! Very odd! Judge for yourselves:

This the result of running an H-alpha colour video from the ZWO120 through Registax. It looked just like that on the live laptop screen as well. 

Today's promised sunshine is a dud. Heavy grey overcast instead of sunny periods. I shall have to get on with mounting the new focuser. I am being driven [all too slowly] by the desire to focus properly and remotely. So I don't have to touch the telescope. At these high magnifying powers the long and heavy telescopes exaggerate their own natural nodding frequency in the wind. Or when excited by a touch of the focuser knob.

I still have new ideas about stiffening up the 20mm thick base fork with another, sturdy, 16mm cross stud. I don't think the pyramidal pier is responsible for image movement. The laptop shelf is mounted directly onto the pier and the image doesn't move when I touch the shelf or the mouse or type on the keyboard.

I brought down the 7" OTA and removed the objective, tailpiece, handles, weight rail and Vixen focuser. Then shortened the main tube by 150mm/ 6". The FTF is about 30mm longer than the Vixen both at minimum length. The turned base ring adds another 20mm. So I added 50mm to the difference. This should allow me to reach focus with the 2" Lacerta prism and binoviewer. It is very easy to add 2" extenders but far more difficult to reach inward focus.

A slight worry is the great difference in weight between the two focusers. Weight at the tail end means moving the OTA up through the rings. There isn't an an awful lot of clearance now. So I'll just have to move the offset weights for the 6" H-alpha 'scope to the top of the 30" long saddle. I already had weights up there but moved them down to the focuser end. This was to balance the added weight of the offset 6" mounted, via tube rings, on the saddle.

After spending so much time on the backplate I changed my mind. I have decided to sandwich the original [saucepan] tailpiece with the focuser collar and base ring. This required I turn a shoulder on the custom base ring. Meanwhile I shall be looking for another saucepan with much less taper.

I put the laminated plywood internal rings back in the lathe and turned the outer surface to better match the saucepan's curve. Then I was able to make use of the original collimation springs in the shorter gap. I reconsidered the sandwich when I realised that I was merely duplicating the FTF rotation system. The custom base ring needs to be firmly anchored to the saucepan base. Then the FTF collar can do its thing. Springs are probably a bad idea with such a heavy focuser on an equatorial mount. It would tend to sag around the optical axis in all positions. So I need to add push screws for locking the collimation as well. All this would be far better done on a straight-sided pan base.

I now have the 7" refractor in pieces just as the sky clears.  The Moon is high in the south, the sun has an interesting spot and my new camera is sitting uselessly on my computer desk.

Click on any image for an enlargement.

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Saturday 13th April Solar with ZWOASI120MC-S + SharpCap

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Saturday 13th. Clear with light winds and a slight, overnight frost.

Sunshine is forecast for this morning at least. A chance to try out my new camera and SharpCap. Image right is a "Snapshot" taken with SharpCap.

09.30 39/37F easterly wind blowing through the open slit. Cloud increasing.

WL: The spot, AR2738, is absolutely superb. Just above centre and a little to the left. [east] It displays a clear umbra and large surrounding penumbra. The seeing is good enough to see fine surface texture at the limit of visibility at 110x.

In H-a the spot appears smaller but surrounded in a vast area of lighter plage. A couple of nondescript proms.

Fired up SharpCap 3.2 and the ZWOASIO120MC-S on the Lacerta prism, to see a superbly even surface texture but with racing cloud. This was not what I was promised! By which I mean the cloud.

The ZWO 120 absolutely destroys any pretensions my Neximage5 might have had as an astro camera. The ZWO hasn't decided it is tired of life [several times before it decides to work] and still needs to shut down [several more times] for another rest. No Newtons rings either!

I was called in for coffee and rolls which coincided with more cloud. Now back to the fray!

Lightning fast at capturing 1000 frames at 60fps. Opened in Registax to show the image superimposed on check cloth!I tried changing to RAW16 and RGB24 but it made no difference. Even PhotoFiltre 7 made checks out of captured stills! Resizing immediately got rid of the patterns.

Now I'm battling with wind and clouds! The cloud continues as I seek help with the patterning. It is debayering [or demosaicing] which I need to address. I managed to run one video through Registax and the resulting image can be seen above. I think I may have overdone the after-treatment in PhotoFiltre as I removed the apple green colour from the Baader Solar Continuum filter. Too much grain.

https://youtube live video AR2738

Click on any image for an enlargement.

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Oh dear?

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Plans for my new saucepan at the tail end of my 7" refractor have been put on hold. Measuring the inside diameter, across the base with a vernier caliper, proved I had been much too optimistic. There was difference of 20mm compared to the 202mm OD main tube. The plan now is to open out the existing, thick plywood ring at the tail end of the OTA before shortening the main tube. 

I shall add a flat aluminium ring cut from sheet metal and then fix the focuser base ring on top. Any worries about the focused beam from the objective causing charring of the plywood can be safely ignored. The sun's image should never fall outside the usual metal baffles in the main tube. With an even bigger hole, to clear the truly vast FTF3545 drawtube, the risk falls to zero.

The fine weather has broken with dark cloud and a short, but visually heavy snowfall this afternoon. Fortunately it was soon removed by 38-40F temperatures and short sunny periods. It was never worth opening the observatory to do any solar observation or imaging today.

My pretty, new, ZWO120MC-S camera and tilting adapter have arrived. With the USB3 cable and my laptop I'm hoping for much shorter guiding demands. The tilter adapter they sent is actually a T-S example and cannot even be used with the ZWO! The adjustment knobs/thumbscrews would remove the finish and even some metal from the camera body long before it was able to be screwed up tight. 

So I have had to reverse the tilting plate adapter and have the adjustment knobs/thumbscrews facing forwards towards the telescope. A much longer T2:T2 adapter would have solved the clearance problem but would have required much fiddling in a rather small gap. 

Careful examination of illustrations of the "real" ZWO tilter suggests larger thumbscrews placed further apart. Why would the camera makers offer a tilting adapter which would not fit their own cameras? I shall have to email T-S to see what they have to say. I did order a ZWO. The thumbscrew heads are rather long and could easily be changed for alternatives. Once the required tilt is added the adjustment thumbscrews become largely redundant.

The camera works fine in SharpCap. With a truly impressive window size compared with the measly iCap 2.4. I tried it with the ultra wide angle "whole sky" lens just to get a live picture. The Neximage5 has been an irritating time waster from day one! Leaving aside its very poor and long outdated, technical specs. The constant disconnections at the pitifully loose cable socket has made its continuing use a complete and utter farce! I'm amazed my laptop doesn't have the "ERROR CAMERA LOST" burnt permanently into its screen! Even with careful cable dressing and secure fixing the damned Neximage5 would lose contact!

There is one very odd detail about the ZWO: While scanning quickly through the ZWO instructions it suggested that the 120 camera can only manage 60FPS during Preview. During actual recording this drops to only 20FPS. As I use SSD internal and external hard drives on my laptop I shall have to check whether the much lower recording speeds were referring only to "normal" HDD recording.

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Collimatable focuser back plate.

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Having finished the base ring/adapter I could then proceed with turning the collimatable back plate. 

It started as a 20mm thick slice from a length of 180mm / 7" round aluminium stock. I removed a core disk from the centre of the disk [from both sides of the disk] using a parting tool. 

Not ideal, on a disk, because of the depth of the tool jamming in the curved cut. So I swapped tools midway for a dovetail shaped tool to allow more room for the deep, parting tool blade. 

A 10mm deep groove, from each side, was not too time consuming using manual feed. I had imagined myself chain drilling to remove the centre disk but it would have been far too slow on 20mm thick aluminium. Chain drilling is probably more sensible on steel which would resent a parting tool being abused this way.

Once the central disk had fallen out [image above] I could continue with a boring bar to smooth the hole and open it up to the correct diameter. I was careful to allow clearance for the focuser drawtube. 

Then I made a 10mm deep recess, or counterbore, to the diameter of the focuser base ring. This will ensure firm support aided by a few small, hidden screws from the telescope side.

The image left shows the [black anodized] base ring fully embedded in the collimation plate. The 5.125" x 24tpi thread for the focuser collar is projecting towards the camera.

There is still some tidying up to do on the raw edge of the disk. I may bevel or even curve the edge for decoration and a little extra weight loss. I have a home-made, ball turning tool which could be pressed into service here to achieve a concave radius.

The back side of the disk also needs facing off and perhaps some judicious thinning. Four collimation screws will be fitted in the plate to allow accurate collimation of the focuser with the optical axis of the 180mm/ 7" objective. [More to follow.]

Thursday: I tried to put a curve on the collimation plate but my home-made, ball turning toll wasn't up to turning such a large diameter. So I turned a series of steps and bevels just to see what it might look like. I realised afterwards that I could use one of my very long, wood turning chisels. To scrape a curve with a round nosed chisel on a tool rest. I have no idea if it will work until I try.

Don't you just wish that once in your life you has an original idea? As soon as I turned to today's master reference of all things practical there were hordes of aluminium turners on wood lathes wielding long series bowl gouges. No wonder. It is dead easy and provides fast material removal if you avoid chatter.

I went back out before dinner and used three of my Marples bowl turning tools. A rub with maroon Scotchbrite fibre with the lathe running smoothed any remaining tool marks. Very satisfying work too. If you don't mind the huge quantities of woolly swarf. I imagine the original brass tail plates on classical telescopes were either spun or cast.

Friday: I cut back the curve on the back plate slightly more.

Click on any image for an enlargement.

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FTF3545 custom base ring machining.

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DO NOT DISMANTLE YOUR FOCUSER OR ANY GUARANTEE WILL BE VOID! 

DO NOT BLAME ME FOR OUR OWN IDIOCY IF YOU COPY MY EXAMPLE!

 Please ignore any marks or dust on the Feather Touch focuser you see here. These are entirely my own fault from frequent handling for taking measurements, etc. The focuser was absolutely flawless on arrival and superbly [double] packed to survive the worst disasters.

Note that I have a very long lifetime's experience in a whole variety of mechanical work, clock making and restoring, cycle and vehicle mechanics, building and maintaining my own cars, motorcycles and cycles, machine workshop practice, making telescopes, optical instruments and mountings, machinery maintenance, scale modelling and building my own hi-fi turntables & pickup arms, etc.etc.

I'm not bragging. Merely pointing out that I have some experience at fixing things which were not broken. I was prepared to take the risk in dismantling the focuser even though Starlight Instruments, very sensibly, told me not to. I shan't show how I went about it in case it encourages the ham fisted. There may still be those who find interest in "exposed parts."

First I removed the pinion housing which allowed the focuser to break down to its major, constituent parts. This avoided using too much guesswork as to turning the base ring to fit the focuser. 

I started by boring 1cm into the top of the base ring in the lathe. Then I opened it out to the correct diameter to just fit over the 3435 housing. More boring followed to achieve a perfect, sliding fit.

Then I could cut a bevel on the inner edge of the ring to lower the ring enough to engage the collar thread. After that I had to reverse the ring and turn a shoulder into the other side of the ring for the drawtube stop screw.

I was aiming for a deep engagement of the collar on its thread while simultaneously, almost contacting the faces of the housing and the base ring.  A close up of the telescope end of the focuser main housing with collar withdrawn as far as it will normally go. Note the bevel.

 The focuser collar with the base ring newly fitted. The collar has a fine, embedded O-ring to achieve a subtly adjustable and non-damaging grip on the base ring. Which FT call an "adapter" since it usually adapts a focuser to a given OTA.

Still in the lathe, the collar and main housing are all fitted together before I dare to remove the base ring from the chuck. Which would lose perfect concentricity.

Another view of the main housing with collar and base ring fitted. Inside the housing, the small gap between the housing and base ring is almost closed.

The telescope side of the base ring showing the shoulder to clear the drawtube stop screw. I went on to deepen it further after taking the photograph. This side will fit into a counterbored housing in a 180mm diameter backplate.

The bored out base ring almost completed. I am smoothing and polishing the bored out surface where it rides on the housing. A nice fit is desirable to allow the entire focuser to be rotated smoothly once the collar is slightly loosened.

The stainless steel, helical pinion of the 3545 focuser. The brass component is the pinion brake.

The collar and housing with the complete pinion and knob assembly in the foreground.

Those who buy a Feather Touch focuser will usually be fitting it [or having it fitted for you by the dealer] to a commercial OTA. Starlight Instruments makes a whole range of adapters to fit their fine Feather Touch focusers to these telescopes. NO dismantling of the focuser is usually required. 

I wanted to fit my focuser to a heavy backplate so chose to follow a different route. My thanks go to Starlight Instruments for their expert advice and to Teleskop-Express for supplying the superb focuser. 

T-S also made me a custom base adapter ring to a very high standard within two weeks of accepting my order and rough drawing. I gave T-S no instructions to turn the inside of the custom ring because I had no idea what was required until I received the focuser. Having a lathe allowed me to modify the custom base ring myself to fit the FTF3545B-A to match my own needs.

Click on any image for an enlargement.

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