31st December 2019 Waiting for the sun!

*

Tuesday 31st 41F. A rare cloud-free start to the day though breezy from the west. As I enjoy morning coffee I am watching the shadows of a neighbour's trees descend slowly down the dome. 10.00am and the shadows are still covering the lower half. The wind is supposed to turn north westwards. So I should be free of the telescopes shaking when I eventually get a clear view of the sun. The trees behind the dome are rocking and my large, but obsolete, Met Office anemometer has just started to twirl. Always a sign of a good breeze. The forecast is for 25mph gusts but falling slowly all day.

10.20. Still a sharp shadow of the top branches on the dome. 10.45 should provide a clear sun. So I had better get set up.

10.50 and still waiting for the sun to clear the top branches.

11.00 Still heavy shadows rocking across the sun's image.

Carried on capturing videos until 12.30 and early lunch. Sharpness is poor as can be seen from the image. Even after beating it to death with iMPPG and PhotoFiltre I couldn't bring out the smudge visible on Gong H-a. 

13.00 Already clouded over! Extended lunch.
14.00 Still clouded over. Doing a meridian flip. Chimney total eclipse of the sun!

14.15 cleared long enough for more captures. Local solar altitude only 7.5°! The roof beckons!
14.50 Sun below roof. 2x Barlow on changed prom on last dregs.

*

30.12.19 Year's End Future Plans?

 *

Tomorrow, 31st December 2019, is finally promised to be sunny all day. Starting windy from the NW but dying down over the course of the day.  That shouldn't bother me too much with the sun in the SE until lunch time. I am getting fed up with losing captures to wind movement. The 7"  f/12 is quite close to the slit and today the wind was straight on. Barely a second passed without some bodily movement of the sun on the monitor.

Initial thoughts are to resurrect the folded 7" OTA. Which has been in storage since I rebuilt the long, straight version. It's not as if I am using a dewshield on the 7". That would just catch even more wind. No dewshield means some dew. Dew heater bands can solve that problem. The open framework of the folded 7" would avoid wind problems but means a hot, unfiltered beam being folded back and forth within the open framework. I don't think the folding [coated Zerodur] mirrors will be much bothered by the heat. Nobody else has access to the observatory so the risk of personal injury is limited to my own idiocy.

I can also remove the 90mm Vixen f/11. Which is hardly ever used but helps to balance the asymmetrically mounted, 6" H-alpha OTA. The smaller refractor is handy for a quick look at the sun in white light and has a permanent solar foil filter over the objective. The 90mm adds some weight, moment and only a very little wind drag.

With the new, 6" f/10 lens coming over the horizon I really have to decide how best to proceed. I am now concentrating almost exclusively on H-a, solar imaging. No point investing so much time and expense unless I maximise my results. I have wasted decades without any serious goal for my astronomical activities. In fact most of my time has been spent building equipment rather than actually looking at the sky. The local trees and tall hedges made observation extremely limited. Which is my excuse and I'm sticking to it.

I could just mount the 6" H-a OTA alone on the big mounting. Or even use the Fullerscopes MkIV mounting? Though that doesn't have proper drives since I cooked the poor old, original, Fullerscopes VFO, drive controller with 7 hours of Mercury Transit. That was with the 7" aboard the MkIV! The old mounting is still functional, thanks to its replacement, stainless steel shafts. Though it could do with a new paint job after years of living under a leaky tarpaulin. The MkIV can easily handle a 6" f/10 and has a massive, welded steel pier to support it. But where would it be sited? No point in returning to the ground where the view and thermal effects from the shrubbery are concentrated.

Despite the endless problems with the AWR stepper motor, Goto drives I have become completely spoilt by the drive accuracy. Both adjustable speed control paddles are very user-friendly. That is when the drives keep going and it doesn't stop tracking apparently randomly. The ease of moving the sun around in the camera's small field of view is quite mind blowing and would be very painful to give up now. I probably shan't live long enough to fit a fully working AWR system to the MkIV. Not to mention the expense.  A new VFO controller might be doable though. 

*

30.12.19 Solar?

 *

Monday 30th 42F some intermittent sunshine appearing at 10.30 after a false start, earlier this morning. When more low cloud arrived. Sun very low and the sky is still full of fast moving, low cloud. Probably a waste of time trying to do any imaging. Gong Ha shows a white smudge in the southern hemisphere but little in the way of proms.

Pm. 14.00 45F. Sky cleared but a strong, gusty, southerly wind blowing straight into the dome and moving the telescopes around. The house chimney is totally eclipsing the sun! Sawed off the motor support bracket to clear the helical focuser. Needs still more metal to be removed but the motor tuning is still working. Quite a sharp image until the chimney intervened. 6" H-alpha objective is slightly steamed up inside.

14:20 Now the sun has cleared the chimney but the telescopes are shaking. Strong, thermal wave agitation of the disk and limb. Just when things could not get any worse, low cloud is scudding across. Fps dropped from 280 [800x600] to about 75fps. Captured a couple of 1000 frame videos but they were shortened by cloud crossing the sun.

4:25 Sky rapidly becoming completely obscured with low, racing cloud from the SW. Disk just visible through the cloud to the naked eye without discomfort. I might as well find something more constructive to do.

*

29-12-19 Minor dome repairs.

 *

Sunday 29th 33-36F, dark overcast again. I extended a ladder up past the mounting to reach the top of the observation slit. A little cycle oil on all four draw slides [top and bottom] eased the remaining friction. The shutters could be then safely closed again from the dome floor. My wife spotted me standing at the top of the dome and saw me as a tank commander in my trapper, lambswool hat.

The top of the dome is showing the same damage to the paintwork as lower down. If I'm lucky there will be warm, dry spring and I can put a couple of coats of paint on the dome to reseal it. There will have to be some rubbing down to get rid of the loose undercoat primer. I expect the wood treatment paint would have been fine without the crappy, white undercoat.

I went around tightening the screws clamping the rubber skirt to the dome flashing. I had used stainless steel nuts and bolts. So they never corroded enough to remain tight. Particularly when subjected to the continuous rocking action of the skirt in the almost continuous wind. Nevertheless only one screw had fallen out since I fitted the skirt. I found it lying on the veranda. The nut and load spreading washer were still inside on the dome base ring.

While I was busy on other things, I gave the red diode string battery an hour of recharging using the diode table lamp on the desk. With the little solar panel placed close against the table lamp diode, the performance quickly returned to normal.

 

*

28th December 2019 Winter and recalcitrant dome shutters!

*

Saturday 28th 30-33F, frosty overnight but now with a heavy overcast. The serial grey skies continue.

I spent some time clipping the string of red diodes to the inner edge of the dome's base ring. The string [green twin flex] used to be laid loosely on the top of the base ring but always looked untidy. The solar panel control box/battery unit had almost run out of juice through cold and lack of sunlight.
The diodes provide too little light to spoil my night vision. They only help to show the limit of the floor space. Or rather the inner edge of the dome's base ring. Which can approach the limit of seriously overhanging telescopes. Usually the binoviewers cause the problem. I can't get my head behind them at certain object heights.

After that I went round tightening every screw and nut on the mounting. It seemed to help the overall stiffness when the telescopes were manually pushed back and forth. Having opened the shutters to let some light in they wouldn't close again. They were dragging at the top for the very first time since I built the dome.

Standing on a crate didn't help. I still couldn't get high enough to use the shutter's own inertia. So I had to drag a stepladder up the steep ladder to the observatory floor. The heavy duty, drawer slides at top and bottom are fully covered  by the shutter "boxes." So it may just have been local icing. Pushing the shutters closed at half height solved the unusual friction problem.

The shutters have been remarkably easy to close until today. Usually I just gave them enough of a tug to get each whole shutter moving as one unit despite their inherent flexibility. Then they would close tightly together without the least gap between the inner ribs. There is, of course, an overlapping weather strip of ply to shed the rain from where the inner shutter ribs come together. Initially, I had planned to have cords over pulleys to pull the shutters closed together at the top. It was never worth the effort to fit them until now.

I made the shutters slightly too wide to ensure they would meet. So there is an air gap between their outer ribs and the fixed ribs on the edge of the dome's observation slit. This provides some air movement when the dome is closed in hot weather. Despite letting in some light the gaps have never leaked even in driving rain with a gale behind it.

The ability to open and close the dome in mere seconds is a major advantage of domes. It allows much greater freedom to use the telescopes in changeable weather. Many amateur astronomers have to carry everything outside and set up from scratch every time they want to observe or image. The mounting usually has to be re-aligned to ensure accurate tracking. With a permanent observatory none of this is necessary. When the choice is between going out in the cold, or watching TV, the observatory will win every time over the open lawn.

Being sheltered from the local breeze will depend on wind direction and where the dome [observation slit] is pointed in the sky. Fortunately my site enjoys SW winds while I am usually pointing the telescopes at the sun in the SE all morning. Much the same orientations exist after dark with the moon and planets. There is a wall of tees to the west. This helps to dull the wind but robs me of seeing objects in the western sky.

Only after lunch, with the meridian flip on the sun, will it sometimes become breezy in the dome. I even have a better way of coping with cold, breezy conditions. I add a tubular, fleece, "polo neck" to my usual, winter outfit. It makes a huge difference not to have the wind whistling around one's neck. Though I usually wear collared jumpers under my down jacket and wear a trapper hat, these do not offer the same protection as my simple, fleece neck "sleeve." Highly recommended if you can find one.

Skiing salopettes are very useful to avoid cold legs and feet if you are sitting for long periods in the observatory. These insulated over-trousers can usually be found for small change in many charity shops. My latest winter observatory wear is a pair of fake-fur lined, "snow" boots. Bought cheaply online and good for -50C! I haven't had cold feet since I've tried them. My feet slide effortlessly in and out of the boots thanks to the glossy fur lining. Far easier to don and remove than my usual walking boots.

*

25th December 2019 Season's Greetings.

*

My apologies to anyone who found a post here obviously aimed at another of my blogs.
Google has the nasty habit of changing any New Post to another blog without apparent logic.
I have now deleted the New Post on both blogs.

Have a good one. If you can.

Thursday 26th 41F: Tidying the observatory of accumulated materials, junk and tools from recent projects. I have also added more screw hooks to the dome wall framework for hanging cables and other occasionally used items. Like small mirrors and hair driers for examining the objectives and then drying them of dew. 

I'd like to organise the cables and USB "boxes" on the desk. Move them onto the pier if possible. Though the same cables still need to reach the laptop when it is lying on the desk. I don't leave the laptop in the observatory and don't think the Wifi would work with the laptop resting on the sloping side of the pier. I shall have to check this before making any assumptions. It would be quite handy to have the laptop out of the way once it has been switched on. The keyboard, mouse and monitor then take over imaging duties.

That was interesting. Lying flat on the desk, laptop hinge towards the house, the Wifi internet speed is 20-22Mbps download. On edge it drops to 5-7Mbps. Yet the router indoors is on a vertical surface with 3 antennas pointing vertically downwards. Which makes no sense that it won't work with the laptop also vertical.  Resting near vertically on the hinge the speed is 13Mbps. While lying flat, the laptop seems immune to telescope position at a steady 22Mbps. All other laptop orientations are inferior. The top flap seems more radio transparent than the bottom of the laptop.

*

Lower profile DC Motor driven etalon tuning.

*

A shorter 240mm timing belt turned up in the last post before Christmas. It had been out of stock at the Danish online dealer. I was unable to use the belt in same way as before without doing some metalwork. That would involve drilling and threading two new holes in the small motor bracket. Not major surgery, but I wanted to keep it simple if anyone wanted to copy my idea.

The heavier and larger motor bracket, supplied in the Skywatcher clone, focuser kit, had its screw holes lower down. Which meant the shorter belt would provide a lower profile motor siting. The downside was the necessity to file a curve on the ends of both the motor mounting bracket and the attached motor plate.[See arrow, image upper right.] 

Ideally, the heavier motor bracket should be chopped off at the X in the upper image. Otherwise the unwanted tail end of the bracket will foul the helical focuser. I haven't sawn the tail end off mine yet because I am still looking at different motor mounting options. If you don't have anything in the way you can save yourself the bother of sawing off the unwanted end.

To be on the safe side I removed the two tiny screws and filed the bare motor plate in the vice. I didn't want metal dust getting inside the motor/gearbox housing. Besides, it would be very difficult to hold the motor still while coarse filing.

The second image [lower right] shows the original layout with the longer 250mm belt and smaller motor bracket. The difference in motor height isn't huge but is probably worth the effort if you can obtain a 240mm belt. 

If you are willing to make a new motor support bracket, completely from scratch, you can lay the motor on its side using a shorter belt. This would require a much taller bracket, after the 90° bend, to match the needs of the motor slots.

*

21.12.19 Wifi problems cured?

Saturday 43F: After a long, grey start, the sun came out too late in the morning. So that it was already over the house roof.  Not ideal for good seeing conditions at this time of year with the sun so low in the sky. I rushed out and set up just before lunch. Synced and tracking but with the shutters blocking the sun. So now I'm ready for imaging as soon as lunch has gone down. Gong Ha shows a hedge-like prom at 10 o'clock but little more than small, bright smudges on the disk.

I want to try to get some temperature readings at focus without the PST etalon and following filters. No chance! The moment I was back in the dome, cloud covered the entire southerly horizon. At least it proved that the telescopes are blocking the Wifi. As soon as I sent them back to park [horizontal & facing east] the internet immediately came back on again. I'd previously tried all sort of heights, positions and angles for the laptop but nothing helped. The signal is just too weak.

The indoor router was always pressed up against the sloping, attic ceiling at waist height. There was nowhere else for it except on top of the rarely used printer. This meant no air around the antennae and the full thickness of the roof for the wireless signal to pass through. Before crossing the yard to the dome. About 15-17m away from memory. [40'-50'.] I had no desire to stretch a cable across the intervening gap. The indirect route over there, from the house, is more like 30 meters with lots of changes in level.

So, before investing in a Wifi repeater I have moved the indoor router. It is now vertically on the wall near the top of the projecting, dormer "box." Where it can "see" the dome through the window. Whether glass is more radio transparent to radio waves, than 12" of rock wool, the roof covering and thick lead flashing, is anybody's guess. I shall check tomorrow to see if it helped reception in the dome.

The wireless Internet was just far too variable over there in the observatory without obvious cause. Other than the three, large, metal telescopes literally hanging over the laptop on the desk below. ASCOM kept saying it had lost the server today! I had no idea it needed one. How on earth can you run an ASCOM driven eq. mounting at a dark site well away from the Internet? Or with a typical US, UK or Australian, rural bottleneck? Does not compute!

Moving the indoor router has worked wonders! 30+Mbps download and 50+Mbps upload on the laptop flat on the desk, out in the observatory. Normally I would have to put the laptop on top of a box to get any reception under poor conditions.

I deliberately slewed the telescopes over the laptop and nothing much changed in Wifi speeds. Slight improvement in upload speeds if anything. Playing 60fps 4K YT videos went smoothly. I just had to tidy the four, white, dangling cables, indoors with some tie-wraps. Only further tests in different conditions will prove if I have overcome the previous Wifi problems. Though the change in router position seems to be a huge improvement.

Monday. Another grey day. Went back over with the laptop to check Wifi reception in the dome. With the telescopes parked it was over 20Mbps down and 50 up. The latest download of Malwarebytes Free is broken. It refuses to let me online whatever I try. It has done this on both my computers now and I have had to uninstall it. Reinstall? Exactly the same problem on both. 4.01.49? I've been using it for years and it hasn't behaved like this before. Found a replacement.

A new [faster] version of iMPPG is available for download from github:

imppg-win64.zip

*

19.12.19 Poor sunshine?

*

Thursday: It brightened up later in the morning so I set up for imaging. No Wi-Fi internet in the dome and HitechAstro focuser motor controller won't play with ASCOM again. Locked up the laptop requiring several restarts. Dreadful seeing conditions today with strong thermal currents on the solar limb and image softness. It stayed bright and clear for most of the day but video captures were few. I tried to capture the visible proms but the contrast was just too poor. The forecast was for a long, grey day.

Even with well-tightened 2" fittings, with three thumbscrews per joint, there is still sag at the camera end on my long PST stack.

I have dug out my 160mm steel tube which I had been storing in reserve for an improved, 6", DIY, H-a, solar refractor. This will allow much more space behind the lens where the CR150 has grazing incidence in a very mean, 140mm Ø Celestron tube.

I'm still looking at a rigid means of support for the PST filter stack. Being equatorially mounted means the stack must be fully supported regardless of orientation.You can't just extend the telescope's main tube backwards because you need full access to all the fiddly "bits and pieces."

So an open skeleton is indicated. A single, tubular beam would provide best access but may flex too much. There are no small enough, hinged tube rings for 2" fittings. Though there are "finder" rings. With extended thumbscrews for centring the image with the main telescope. These might offer what I need. I shall investigate what is on offer. £100-200 for a couple of Chinese cast alloy rings and a dovetail? You can't be serious? Definitely another DIY project in my stars.  

*

18.12.19 Motor etalon tuning in practice.

*

Wednesday 18th December 2019, 11.30am, 42F, highly variable, fast moving cloud. With only occasional clear periods. Breezy from SW and blowing the telescopes around. Small proms at 2 & 8 o'clock on the limb. Nothing much visible on the disk. Gong Ha agrees. Sun at ~12° altitude at 12.00.

The PST etalon is moving as expected under motor power. Though I'm getting so few clearances that its effects are difficult to judge. Trying some 2000 frame captures of the disk at 320fps 800x600 on the ASI174 in SharpCap. The hope was that I could capture the 2 o'clock prom as well as the disk. Plates of low cloud becoming established! Clear blue overhead much of the time. Or higher, fluffy cloud.

My wife has bought me some huge, Kamik winter/snow boots for Christmas at a ridiculously low price online. So I'm trying them out. I have been really struggling for foot warmth in the observatory before now. These still feel comfortable after an hour in the breezy dome. They should do too with a -50C / -58F rating on the [still] attached label. They slip on and off effortlessly. I could never be bothered with my walking boots. Too difficult to get on and off and then there were the fiddly laces.

I'm wearing my new, fake lambswool, "trapper" hat too. This covers my ears and neck where the wind usually whistles. I really ought to dig out my old duvet jacket with a hood for even more protection. These breezy condition really makes it feel much colder thanks to wind chill. That's the advantage of a rural observatory. Nobody can see how silly you look! Comfort is far more important than appearance. As long as you aren't daft enough to share images of your get-up.

12.30 and that's over an half hour without a clear view of the sun. Following the sun with the dome slit is effortless with the drive crank being so near my computer chair.

It was nearly 1300 before I could finally capture more of the disk. The cloud to the south does seem to be sinking slowly towards the horizon. Just in time for lunch! Well past the meridian now so I should do a manual flip before I'm called in. It's best to wait as long as possible before making the flip. Then the telescope tails don't try to hit the pier or overhanging monitor. Nor try to brush the laptop off the desk!

Luckily I can add a lot of westerly travel on the Simple Handset [paddle.] Then the mounting slowly corrects any changes I made at the end of its initial slew. Though you can't do anything manually. Start pushing or pulling on the telescopes and the mounting will be completely lost. It must always be driven by the stepper motors.

Lunch over and the sunshine is looking very watery. By 3pm the house was casting a shadow half way up the dome and I'm in the bottom half. I told you the sun was low at 55N! Stellarium says only about 11-12° high at maximum.

For my next trick I'm going to beat Windows 10 around the head if it doesn't start saving my videos onto my external SSD! I've told it countless times but it never, ever listens! Why bother to ask me what I want it to do with the external HD if it then completely ignores my choice? #"X¤%X&*! It's a good job Big Brother isn't listening! Isn't it? 😏

I had to snigger. The big American & global IT monopolies are getting together to agree SMART standards. Supposedly to get smart objects to talk to each other. Don't they really mean agreeing advertising standards to show on very smart object screen regardless of the maker?

YouTube is rapidly becoming completely unwatchable. With an advert aimed squarely at the mentally handicapped showing before every damned video! This is what the Sci-fi authors really meant by dystopia. Zombies with mashed potato brains. Raging against intolerable levels of advertising in every waking moment.

*

16.12.19 Shorter timing belts finally arrive!

*

Monday 16th. Three weeks and three days after posting, my shorter timing belts from the UK have finally arrived. Avoid Standard International Letter Post if you can. £2.80 worth of postage for nothing at all. Let's call it Substandard and be done with it.

My DC, focuser motor driven, PST etalon tuning has been on hold all of this time. I couldn't get enough tension with the 280mm without adding a foolishly long, extension bracket for the motor. I'll leave the clumsy motor arrangements to the ridiculously expensive, commercial, motor units. I much prefer the most compact motor siting with nothing sticking out. Like I did for my big, Feather Touch FT3545 focuser.

Hopefully, I will now be able to complete the project in a short time. The new belts are 250mm 2GT with another of 240 mm still waiting for stock to arrive at a Danish dealer. I shall have spares for other projects.

The belt drive with 16T pulley and 250mm 2GT belt. The angle of the motor bracket needs to be reduced slightly. It is more than 90° as supplied. The bracket is only soft mild steel. So a vice, adjustable spanner or pliers will bend it to 90°. I don't recommend trying to bend the bracket by pressing down on the motor!

I want to drive the helical focuser as well on the H-a telescope. Though that presents even more problems because both ends of the focuser move in opposite directions. The belt will fall off either end of the focusing ring during full travel. At least the ring rotates smoothly and easily. I shall just have to support the motor with sky hooks. Or off a separate bracket not directly attached to the H-alpha OTA.

I have also been stalled on finding a suitable replacement for the original and far too tight, PST etalon band packing O-rings. Several sizes of O-rings were tried but all were too small in diameter. Leaving a lot of play in the outer ring of the etalon tuning band. I tried various strimmer or [US bushwhacker ?] monofilament cord. That was either too tight 1.6mm or too loose in 1.3mm. Most electrical flex had 1.3mm cores and was therefore much too loose. 1.5mm Ø would do but nothing in everyday materials presents itself.

The new 250mm 2GT belt fitted nicely with a 16T pulley on the motor shaft. The 20T needed a curve filed in the original motor bracket to allow the motor body to sink into the bracket. Without the filed curve the 20T made the belt far too tight. I am still trying to lower the motor even more by rotating it by 90° to the bracket. It might then be possible to use the 240mm belt I have been waiting for. We shall have to see if/when it ever turns up.

I swapped original PST O-rings for 1.3mm monofilament strimmer line. When motor driven a bit of play in the tuning band is irrelevant. The motor and belt tension will always hold the etalon in the chosen position Allowing fine tuning without touching the telescope.

Pictures and quite possibly, a YT action video of my motor driven, remote etalon tuning in daylight tomorrow. If it ever gets light! Heavy overcast and fine drizzle. You'll have to make do with a flash image, or two.

The motor happily drove the etalon form end to end of its travel in both directions. See the very dark video at the top of the page. Despite being taken at lunch time it never became fully light today.

I had another thought after carefully centring the belt on the tuning band. The PST O-rings are heavily offset to one side. So the drive belt really ought to be centred over the O-rings. Even if it will look all wrong.

*

Sunday 15th Storm in [an inverted] teacup!

*

Sunday 15th. A storm passed over in the afternoon with rain in the morning. I noticed the south facing dome trying to turn out of the wind during one, fierce gust around 1 o'clock. So I went over to turn the shutters into the SW wind. It was a bit noisy up in the dome. Mostly from the rubber skirt flapping. I added three long F-clamps to the upwind side of the base ring. Though the eight hold down disks have been good enough until now.

Being round, they allow the base ring to slide effortless beneath them. Without having to worry about the truth of the base ring causing digging in. Each disk sits on a strong, SS shelf bracket bolted to each, of eight,  7" industrial roller metalwork stands. With the steering rollers, just below on the same axle, it makes for an efficient and tidy system.

The wind was supposed to peak mid-afternoon with gusts to 50mph+. It seemed like a good idea to park the telescopes horizontally for a change. Low down on the north side of the pier seemed more sensible today. Than sitting up high, parked horizontally, on the south side. If the dome were to move sideways [however unlikely] it won't scrape the telescopes along with it.

The huge, old, plum trees behind the dome are swaying wildly. I hope they don't drop any branches on the dome or workshop! The balance of the massive branches is all wrong for amateur felling. It would need a big tractor in the field behind. With a long chain, or very strong rope, to pull the tree, or individual branches away from the garden during each cut. With the perfect hindsight [of a woman] the tree should have been removed twenty years ago. Now it hangs right over my buildings but I'm too afraid to climb up there to try to shorten each 40' branch in turn. My tallest, 20' ladder hardly reaches up a third of the way! 

*

Saturday 14th Dec.2019. Thermal issues in H-alpha modded telescopes.

 *

The forum discussion on the thermal stresses [if any] in an H-alpha telescope is ongoing. As soon as I see any sunshine I shall measure actual temperatures hitting thin, blackened, metal targets using the thermometer gun at close range. This would seem the best way to confirm real world temperatures, after the D-ERF, where the etalon sits in the beam. I just need to remove the long, filter stack from the focuser. Take a reading of my target. Then replace only the etalon and take readings behind it and at focus.

What should have been a simple procedure of a few moments is being endlessly delayed by the grey weather. We have a storm coming this afternoon with 55mph winds forecast. I am still waiting for drive belts for the etalon ordered a month ago on eBay[UK.] Plus some more O-rings. Which are still untraceable in the post. The local stockist is still sitting on my order for 240mm belts which were "temporarily" out of stock with a promised delivery in 1-2 weeks.

*

Dec 13th: More H-a-musings.

*

Here's a token live video from my heavily modified, 6" f/8, H-alpha telescope. The seeing wasn't particularly good and the thermal agitation, caused by the intervening atmosphere, is self-evident. ZWO ASI174MM [mono] camera. It is views like this which drive me on to continuously improve my solar instrumentation. Solar imagers use videos like this to produce high resolution "stills." Usually adding false colour.

It has been grey for a few days so the discussion on H-a instrumentation goes on. My plan was to add a full aperture D-ERF to my 150/8 OTA to reduce internal heating..

Quote from Baader sales website:  "Our 43-layer dielectric DWDM-coating delivers a COOL-beam of pure red light, with a HBW of 80 nm!"

I had a very interesting response on Solar Chat! forum to my worries about heating effects inside the D-ERF filtered telescope. BobY analysed the heat passing through the "cool" full aperture, Baader D-ERF with startling results. He went so far as to suggest adding [potentially sacrificial] protective blocking filters before the etalon. I can vouch for the warmth of the red focused beam after it passes through my sub-aperture D-ERF and the PST etalon. The Etalon sits in that hot beam for countless hours quite close to focus!

My habit of tracking the sun all day long, on sunny summer days, may well have been stressing my PST etalon. It was a danger I never really considered seriously. Replacement of the PST etalon is a ~£500 bet on getting a good, secondhand one from any random, PST, donor telescope purchase. With rather doubtful odds according to some experienced PST users and H-a telescope modifiers. Some PST etalons are excellent but do seem to be very few and far between. There are even reported to be PST etalons, which are so poor, they should never have left the Mexican factory.

Without a suitable comparison I cannot be sure where my etalon lies in the quality spectrum. It has given me a lot of H-a fun. So I'd hate to think I have damaged it by naively believing Baader's sales propaganda at face value.

*

10.12.19 Sun? What sun?

*

Tuesday 10th 32F, overnight frost. Early clear sky so it's back to the observatory to capture some solar H-alpha.

10:50: Objectives still steamed up on all surfaces. Sun still behind neighbour's tree. Used gentle warmth from the hair drier on the 6". The Lacerta prism is well dewed up too.

Grr! The tree doesn't respond to the hair drier! Variable cloud moving across from the NW but still hope.

Gong Ha shows proms at 2, 4 and 8 o'clock. The 8 o'clock looks big enough to be well worth capturing. I'm missing the correct nomenclature for solar disk positioning. 8 o-clock is presumably SE provided the camera and image are correctly oriented to match the naked eye view.

Got no proms, Dad! Has the etalon gone off band? It is quite possible after all the adjustments to O-rings and moving the inner etalon arc. I might as well remove the rubber band and outer shell and turn the etalon directly with a screwdriver.

11:20 34F Found the 2 o'clock proms. Then the 4 o'clock. Poor contrast against H-a background sky. The objective is still steamed up inside! Now I really have to think about fitting heating bands!

Still trying to find the 8 o'clock proms as a thick plate of cloud moves over the sun from the west. Blue behind, so I'm persevering. A breeze is picking up now. The forecast was for later cloud. Presumably the swing to the south west is bringing the cloud. I've suddenly lost the wireless internet again after earlier success. And now back again after opening Settings > Networks. Curious. Still less than 4 Mbps.


11:40 37F Solid cloud low down now. Only partially blue overhead.

12:30 Back indoors and the sun comes out!  Grr?

*

8.12.19 The future of my solar H-a instruments?

*

For high resolution, solar imagery, aperture wins. Though always within the limitations of local seeing conditions. The larger the aperture the more the atmosphere can interfere. This is the result of the physical size of thermal convection cells. Also because of the inevitably higher magnifications involved. Unless optical means is used to reduce the focal length, the camera sensor is fixed in power or image scale.

The larger solar telescope will provide unprecedented detail but only when seeing conditions favour it. Which suggests a fall-back, smaller instrument for all those occasions when the seeing does not cooperate. Which makes the considerable investment in the larger instrument even more doubtful.

The present "quiet sun" offers reduced opportunity for any instrument to capture noticeable surface detail. [Active Regions or Sunspots] Though the larger aperture can capture what passes unnoticed in a smaller telescope. 

When only prominences are available for solar interest then the larger instrument can really get into its longer stride. Surface detail might also be lifted to the point where it becomes far more interesting in itself. Where a small instrument cannot possibly reach the level of detail required. All of this is largely determined by the skill of the imager with his choice of processing software.

Larger instruments concentrate a lot more heat. Which must be managed by safe filtration. Inevitably that raises the argument for full aperture D-ERFs to protect the instrument from excessive heat. With some reservations about the internal thermal conditions within the instrument. In theory the air itself shouldn't be warmed by the hot beam from an unfiltered objective. 

In practice there are "things" in the way which will almost certainly absorb some heat from a hot, focused beam. The nearer the optical element is to the focal plane the greater concentration of heat. 

I can safely [?] vouch for the fact that my 6" lens focuses a lot of heat. Some of which passes right through the internally placed 90mm D-ERF. [Rejection filter.] I can still burn my hand if I place it in the focused beam without the PST etalon and following filters fitted. 

Is this entirely the fault of the sub-aperture D-ERF? For all I know the D-ERF, with its multiplicity of deposited layers, is designed to work properly, only on parallel light. The light emerging from the f/8 objective is far from parallel. Which might suggest that the filter cannot perform optimally. Baader clearly recommends placement of their D-ERFs in front of the objective. NOT somewhere behind it. 

Well, they would say that wouldn't they? The cost of D-ERFs rises rapidly with increasing diameter. You can buy an achromatic objective [even a complete ED OTA] for less than the price of a larger, Baader [or Airies] D-ERF. That doesn't mean the filter manufacturer's safety advice is wrong, of course. It is eminently sensible and provides a level of safety for all users. Perhaps one not enjoyed by the cost-cutting sub-aperture, filter users, like myself.

There is a move towards Schmidt Cassegrain telescopes for solar H-alpha imaging. The problem is obtaining a full aperture D-ERF within one's budget. There is only one manufacturer [Aries] and the costs are frightening for mere mortals wanting to try these larger apertures. These instruments can't be used with internal, sub aperture filters because of their design. The secondary would be cooked by the concentrated beam from the large mirror even if the filter could be placed anywhere useful. 

Where does that leave me with my desire for more surface detail and increased scale for prominences? I have my 7" f/12 R35 iStar objective. Presently only used for white light imaging with a Lacerta 2" prism. The iStar has a focal length 1.44 x that of the Celestron CR150HD f/8 which I presently use for H-alpha. 2160:1500 [with GPC.]  Given my experience of a hot beam from the 6" the extra heating from the 7" could be considered a serious problem. 

I would like to use the 7" in its folded form to reduce the far greater moment of the long tube version. While the beam folding, optical flats of the 7" are of Zerodur, I really don't want them being baked for literally hours every day it is sunny by the 7" objective. Which means selling several kidneys for a 180mm D-ERF. Ouch!

The much more compact, folded 7" framework would give me a more solid base to support the extended stack of the PST etalon and following filtration. Provided with motor focusing and etalon tuning, there would be no need to handle the telescope during imaging sessions.  A 2" star diagonal could turn the final leg of the beam upwards for a really solid attachment to the OTA. 

*

 

3rd December: Grey weather and new software revelations.

*

Tuesday: 43F, grey, wet and miserable. Literally everything is covered in heavy condensation!

Wednesday: Mid 40sF and grey. I refitted the inner, upstanding skirt of recycled plastic, lawn edging with about 100 screws. Most of the time the inner skirt is not necessary. However the rubber, outer skirt flaps noisily in windy conditions.

I am tempted to see if warming the plastic with the new [recycled] hair drier would allow it to be straightened. The plastic is very stiff and more wavy than I would have liked. Causing occasional, outward waves which rub against the rubber skirt and increase dome, turning friction. The dome is sixteen sided and rotates over an eight sided building. Leading to occasional conflict between flats and points.

Thursday: 45F and grey again. Just as well I replaced the inner skirt yesterday because a storm is forecast for overnight tonight. It is twenty years since the last really big storm. When we lost a quarter of our roof. I went ahead and replaced the whole thing after that. Working alone, as usual. I built two dormers and installed thick insulation at the same time.

I have discovered a [long] YouTube [streaming] video by Steven Tang. A master of solar image processing with decades of experience and frequent accolades. There is lots of padding but some vital detail on bringing out out the hidden detail in the final image. His relaxed and natural approach using the same, free software is quite startling to one who has tried and failed miserably to obtain similar results.

I'm afraid I found the other software help videos too demanding of my limited memory.  It's a shame I can't just install more RAM and a nice big SSD. So I shall just have to note the times on the video when he achieved his magical results. Throughout the video he as doing simple things I had never known existed in the software.

Interestingly, he stated that the Celestron, C6R 150mm, f/8, achromatic refractor was an ideal solar instrument. Particularly when used with a Daystar Quark for H-alpha. I am using an older CR150HD which lacks a collimatable objective cell but is quite similar. His recommendation of larger apertures for high resolution H-a imaging was good to hear form an expert.

Daystar's reputation for quality control of the Quark has taken a battering on the forums. With some very experienced solar imagers returning up to five before they received a properly working example. This is completely unacceptable at the very considerable purchase price.

As an occasional distant, online customer what chance would I have of receiving a satisfactory example? One which actually performs to claimed specification? The considerable delay in tuning is a considerable downer for one used to instant, live tuning with my PST etalon.

On the same subject, I have no idea if I have a good, average or poor PST etalon. Bought secondhand, with a dead ITF, it was never really used as a PST. So I can only judge the results with my 6" refractor. The "live" visual view is usually very pleasing. Particularly with the binoviewers. While the image on the monitor screen from both ZWO cameras has been excellent despite the unbelievable scale. Only my lack of skill with the processing software denies me the final images I desire and know already exist in the frames of the video. If only I could bring it out!

Friday 6th Nov: 46F. The dome is still attached after last night's wind. I shall have to check the rainwater, collection containers. I usually park the shutters facing south but rotated them into the promised wind. I can't make drainage gutters because the bottom of the base ring runs on the big support and rotation rollers. I am still looking at optimum waterproofing options for the entire dome.

Saturday 7th: 43F. Early sun, then cloudy and then clear for a while. Captured some videos of the area of the disk with dark filaments showing on Gong H-a. The nearby proms on the limb were too small and dim to be worth the effort. The AVIs could not be found by Registax or AS!3 [Autostakkert.] So I returned to AS!2. I could clearly see them on the screen under Desktop>SharpCap Captures but couldn't Select, Open or drag and drop!  Then PhotoFiltre7 and iMPPG couldn't find the resulting stills! The sky went very dark at 1pm so I retired for lunch.

*

2.12.19 Hair drier wins!

*

Monday 11.15, 37F, sun after early cloud cleared. Still being teased by long strips of cloud.
Once uncovered the objectives dewed over. So out came the new [secondhand] hair drier. On low warmth it quickly cleared the problem.Then they steamed over again. So further gentle warmth was applied with lots of hand waving of the hair drier. The inner surfaces look misty as well.

First image of knotted prom at 4 o'clock.

I am using a small makeup mirror to see into the objectives well above my head. So much easier than climbing on a beer crate or dragging the telescopes down to my level and then having to re-sync on the sun.

Have I mentioned how C-Du-C/ Skychart keeps talking to me? To which my wife would reply: "What are the voices telling you to do?" 😊  Usually followed by "Is she a blonde?" 😨


There is a rather small, looped prom at about 4 o'clock on the solar limb. Thin cloud is making it difficult to tune and adjust the brightness. When enlarged [zoomed] in SharpCap the prom appears almost knot-like. Small humps and proms at 1 o'clock and ten o'clock. Nothing obvious on the disk.

This second image was processed and inverted in in imppg from the same, still image above.

 
The tiny image was cropped from 640x480 and then false coloured and enlarged to 500pixels in PhotoFiltre7.

12:00, 41F in the dome. Much heavier cloud arriving from the NW. Hopeless conditions for capturing anything except a cold!

13.00. Paused for lunch. The sun has now come out again. I had better return to the fray! Only captured a few images of the same prom as seeing conditions worsened with the proximity of the roof. Sun sank below the house ridge around 15.00.

Having given up on the sun I did some odd jobs until the Moon rose high enough. The seeing was awful! With violent thermal shaking and simultaneous streaming. I captured a lot of videos to have something to play with later.

I have almost given up on Registax and gone over to Autostakkert. Though I have been following on from AS!3 with Registax6 for Wavelets. Imppg is getting some exercise too. As I claw myself up the overhanging learning curve of image processing. Came back in at 18.00 as cloud became a serious nuisance.

*