Going solar. Simultaneous H-alpha and White Light!

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Good Friday was a clear and sunny day with few clouds until after lunch: 

My first real solar time with H-alpha and White Light, under a clear sky. 

My 150mm/ f/8 [working at 120mm f/10 equivalent] and 90mm f/11 side by side. 

The detail is mind blowing in H-alpha. With the fine texture of the prominences clearly visible.

There was even a bright surface feature showing altitude variation near the limb. Several, very small dark spots on the surface too.

In white light the sun was simply featureless.

I started off crunching about [very carefully] on an inch of snow inside the observatory as I mounted the telescopes. The ice and snow weren't melting. So I opened up the southern curtains to let the sunshine in. The eyelets are simply held by projecting, round head screws. So they are very easy to open when needed.

The mounting isn't quite balanced even with both OTAs on board. The 5 kilo weight inboard on the Dec shaft is still slightly too much. The stepper motors struggle to lift a load uphill. So I slacked off the clutches to try and balance everything. It really need an outboard sliding weight on a bar somewhere on the OTAs to manage longitudinal balance. This will aid the balance around both axes. 

All this will change when the 7" refractor is added. I just need to fix the other two OTAs onto the largest. Usually this is easily managed by stacking hinged tube rings. A bit of distance between the various eyepieces is useful to avoid collisions. The same goes for focusers.

It was fun having a chance to use the AWR drives. With four correction speeds, as well as the different drive rates it is very satisfying to be able to move slowly around the sun's disk looking at prominences. Rotating the IH2 [handset or paddle] in one's hands soon avoids confusion over direction of travel. This only occurs when the diagonal is at an odd angle for comfortable viewing.

Click on any image for an enlargement. 

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Going solar: An update.

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I was so pleased with the white light, bino-view of the Sun that I decided to improve the mechanics of the Vixen 90. It is the perfect telescope for solar viewing being so easy to handle while providing a decent sized objective. I just clamp the telescope into the rings of the old MkIII mounting, slip on the home made, solar film filter and I'm ready to go.

First real solar time with H-alpha and white light side by side. 120mm f/10 equivalent and 90mm /11. The detail is mind blowing in the H-alpha. With the texture of the prominences clearly visible. There was even a bright surface feature showing altitude variation near the limb.

The major problem with the Vixen is the inadequate drawtube connection to the heavy binoviewer load it must now carry. Intended only for a solitary eyepiece, the single little thumbscrew has already damaged the nose-piece of the heavy binoviewer plus its two LP eyepieces. No amount of tightening would hold the binoviewer against sag and general floppiness.

So I needed a serious upgrade in the mechanical support of the star diagonal which carries the binoviewer. I could have drilled two more holes for screws 120° apart but searching online suggested a much better alternative. A Baader compression ring, 1.25" adapter which should fit inside the larger screwed ring.

The original components are shown here. The long drawtube has a female threaded ring and another, 1.25"  ring  screws into that. The weakness, for my binoviewing purposes, lies in the single thumbscrew.

A compression ring adapter with three thumbscrews seems the perfect answer. Better images on arrival from Teleskop-Service. I just hope the 36.3mm thread fits the Vixen ring as claimed. It measures exactly 36.3mm with my calipers. Which is the stated size of the male thread of the Baader adapter. Now I need a 90° star diagonal with a compression ring fitting that doesn't cost the earth. My two, dirt cheap 1.25" diagonals were both no-name purchases. I can't honestly say that either of them noticeably spoilt the image. The star diagonal will become the weak link in supporting the heavy binoviewer.

No solar viewing today as snow falls steadily. I dismantled and reworked the rather stiff 1.25" Vixen focuser after noticing an eccentric focusing wheel. The rack pinion shaft was dismantled and put in the 3-jaw chuck of my lathe. I then, very carefully, used a ring spanner to very gently straighten the bent shaft. I realised the extreme danger of snapping the pinion shaft if it was hardened. So used repeated gentle pressure on the ring spanner until the shaft finally ran true when the lathe was spun up.

The grease in the focuser was incredibly thick and took some cleaning to remove it completely. I then added some thinner grease. Careful adjustment of the tiny grub screws followed. These set the pressure on the long pad, on the opposite side of the drawtube, from the rack. To produce smooth and even drag from end to end of drawtube movement. Final adjustment was via the pinion plate screws to achieve smooth rotation of the focusing wheels. The focuser movement now feels much smoother than I have ever known it.

Click on any image for an enlargement.

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Teleskop-Service binoviewer + T-S GPC/Barlow = A problem!

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With the arrival of the S-T GPC/Barlow I was absolutely dumbstruck, well almost, by the repeated and drooling idiocy of the [Taiwanese?] designers! 

I have already mentioned the drooling idiocy of not having a standard 1.25" filter thread in the binoviewer body. The manufacturers use a tiny, non-standard thread. Which completely trashes a great many potential advantages compared with using a standard 1.25" filter thread. Advantages like being able to screw in their very own, GPC/Barlow in place of the empty and completely superfluous nose-piece when a GPC/Barlow is required.

Now add the drooling idiocy of a GPC/Barlow with a standard 1.25" filter thread but UNDERSIZED body diameter for the 1.25" industry standard diameter common to so many astronomical instruments and their fittings.

The idiot designers have made the GPC/Barlow lens 31mm in diameter instead of 31.8mm. Just to be extraordinarily difficult, you ask? Heaven knows, but once again, T-S trashes its potential to be fit for [perfectly normal] purposes.

The Teleskop-Service, Glass Path Corrector/Barlow screws into the far end of the empty, 1.25" tubular nose-piece of the binoviewer. Thereby adding an extra 23mm of [unwanted] length in a completely non-standard and undersized diameter! Length matters because it effects the magnification factor. Less is less! Where less is highly desirable.  

So what happens when you use the binoviewer with its special Barlow/GPC/OCS? The GPC/Barlow/OCS pushes the binoviewer itself out of the intended fitting, by its unwanted, extra length. Now, this might not matter if the binoviewer still fitted into standard 1.25" standard fittings. But guess what? They don't!

You cannot use a Teleskop-Service binoviewer with its matching T-S GPC/Barlow with a 1.25" star diagonal. How crazy is that? The protruding 23mm x 31mm Ø "proboscis" of a GPC/Barlow stops all use of my 90° star diagonals and my Baader 45° erecting diagonal. Even if it entered to a greater depth it would probably crush the diagonal's precision mirror with its delicate, front surface coatings. Fortunately there is a stop ring built into most, if not all, 1.25" diagonals.

Once fitted with its Teleskop-Service GPC/Barlow/OCS, the Teleskop-Service binoviewer can only be used for "straight through" viewing. Let's remember that this is quite an expensive accessory. Mostly intended for use by amateur astronomers. Many of whom may well have noticed that most of the sky is well above eye level. Particularly if higher magnification is desired. The magnification provided by the GPC/Barlow can only be used at higher pointing angles demanding a star diagonal be used to avoid neck strain. Otherwise the poor "seeing" at lower pointing altitudes make high magnifications completely pointless.

So now we have the heavy Teleskop-Service binoviewer, already ridiculously cantilevered out of a flimsy 1.25" tubular fitting. Probably one sporting only a single, tiny thumbscrew for security. With its 23mm x 31mm Ø GPC/Barlow extension the T-S binoviewer cannot even reach its flimsy supporting tube with its single silly little locking screw.

The expensive binoviewer rises to "half mast" on its matching but now UNDERSIZED GPC/Barlow. Being UNDERSIZED it cannot possibly support the already tottering binoviewer. It was never designed to support the binoviewer so they deliberately made it UNDERSIZED so nobody [sensible] ever tried! Had they made it 31.8mm in diameter it could have supported the binoviewer. Even when it was lifted by the 23mm length of the GPC/Barlow.

One wonders whether the drooling designers, or far more likely, the factory managers [all obviously working well above their natural pay grade] have ever used the binoviewer, which they, themselves manufacture. Had they actually tried, they would probably have dived off the factory roof to end their shame.

Can you imagine a car manufacturer offering exclusive alloy wheels for their products? But made the wheels undersized so they wouldn't fit their own cars? Can you imagine them being made with ridiculous extra spacers so they rubbed on the bodywork and caused their cars to crash on the very fist drive? No, I can't see it happening either.

A Glass Path Correcter [GPC] or Optical Correcter [OC] is a form of modified Barlow. It uses a negative and positive lens, in addition to the normal negative "Barlow" lens. This helps to shorten the very long, glass path of the attached binoviewer. A normal Barlow is a simpler, purely negative lens designed to boost magnification alone. It cannot alter the glass path length. The distance from the Barlow to the eyepiece alters the magnification. Because the binoviewer often has 100mm, or more, in glass path length the GPC or OC makes good sense to keep magnification factors within reasonable limits. Despite the claim of 1.6x the GPC often provides 2.5-2.8x increase in magnification at the eyepiece[s].

The 1.6x refers to the glass path shortening effect. A 110mm glass path binoviewer would be shortened by 1.6x or about 65mm. This usually saves sawing lengths from expensive telescope tubes just to be able to fit a binoviewer. Without the optical correction [for glass path length] the telescope would fail to reach focus even when the focuser is fully racked in. A star diagonal adds its own glass path length. Making life even more difficult for the telescope user if they cannot reach [sharp] focus at infinity.

Teleskop-Express: TS Optics 1.6x Glass Path Corrector for binoviewers

Teleskop-Service have informed me that they are considering an update to the T-S GPC but with no date available. There is an obvious communications problem with some of their staff despite their English website service. I have now ordered a 1.25 dielectric, star diagonal with compression ring from a UK dealer. [Fingers crossed, but the long Easter weekend intervenes.]

The original binoviewer dealer has now responded to my safety concerns with an offer on a good quality, 1.25" compression ring diagonal. I hope it will solve the insecurity problem when the undersized GPC is required to support the entire binoviewer and its two eyepieces. More on this, on arrival.

Click on any image for an enlargement.

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Going H-alpha. Barlowing the binoviewer with the T-S GPC.

I had a T-S 1.6x glass path correcter with Barlow in the post. Due to the distance to the eyepiece the resulting power will lie between 2.6x and 2.8x. So a 32mm EP will effectively become a 12mm. Whether the PST filter stack adds further power, due to path length, is still an unknown. More on this later.

The S-T GPC+Barlow duly arrived in the post today. It screws into the internal filter thread of the binoviewer's empty nose piece. Another utterly wasted opportunity!

Firstly, the GPC is smaller in outside diameter than the 1.25" fitting. Had it been the same size it would have provided valuable support for times when the binoviewer cannot be pushed right into a fitting.

Secondly, the S-T binoviewer has an undersized body thread compared with a standard filter thread. Just imagine if they had the imagination and daring to have fitted a standard 1.25" sized filter thread in the binoviewer body. Now anything and everything would fit the body. But no!

The empty binoviewer nose piece could be simply unscrewed and the GPC or Barlow[s] with 1.25" OD fitted directly to the body. Assuming, of course, it was the correct 1.25" diameter. Instead of which the daft GPC will not even fit into a standard 1.25" star diagonal when attached to the binoviewer! How crazy is that! Nor will it fit into the blind end of the PST eyepiece holder without pushing the binoviewer too high to clamp with the thumbscrew! Now what?!!?

How utterly futile! They chose a non-standard, undersized thread for the body which cripples all the huge potential had it been a standard 1.25" filter thread. Argh!! Ooh, it does make you cross. Well it makes me angry, anyway.

I fitted the binoviewer, fitted with 26mm Meade 4000 Eps without GPC/Barlow in the Vixen 90mm with a Baader Solar film filter in place. The Sun was now nicely large, sharp and 3D but completely unblemished by any of the typical features. Unfortunately it was a day plagued by cloud. With only rare thinning and almost no blue patches at all. It was slightly amusing to see the clouds crossing the 3D sun but visibly behind it. 

When the GPC arrived mid-afternoon I added that to the mix and enjoyed much dimmer but larger views of a sun behind clouds. There was almost no free focusing movement left [at all] without the GPC and 65mm left with it fitted. I couldn't use the 1.25" star diagonal without the GPC. The 45° Baader diagonal used up far too much light path to work at all with the binoviewer regardless of fitting the GPC.

The major mechanical problem is the Vixen's single thumbscrew and very loose [oversized] eyepiece holder. It will not support the binoviewer without cosmetic damage and a general floppiness.

Click on any image for an enlargement.

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Going H-alpha: T-S binoviewer first review II.

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The next greater distance was much more difficult. I hung my inverted piece of printed paper from a tree along the drive at 80 yards. Now I was struggling to read the 3mm [1/8"] high bold text headings due to local thermal effects. The sun was bright but quite invisible behind the thick cloud but still warmed the intervening, overgrown lawn and the air above it. There was a ripple to the edges of everything including my printed piece of white paper.

The cantilevered binoviewer really needs a diagonal brace to support it on top of the PST filter stack and eyepiece holder. But where to fix such a brace?

I could easily see the text, but was unable to read it until I inserted a very odd pair of no-name 20mm eyepieces. One presumed Plossl and a plastic one one marked R-K. Possibly from a Bresser Skylux 70mm refractor.

Now the bold text was legible but I could not read the 2mm high text and figures in normal weight of type. Though, I repeat, all the text was easily visible. A fly became interested in the paper and was easily seen at this distance as it flew around.

I had to work much harder now to get the images focused for each individual eye. Clarity was very much better using both eyes. There was also a much wider apparent field of view with these 20mm compared to the Meade 4000s. Which were rather like looking through a tunnel in comparison. 20mm gives 50x magnification and would make a great birding telescope on a pond. Though the long and rather heavy Vixen hardly lends itself to portability and needs a really sturdy stand. I have used a video tripod with this telescope to take handheld snaps of eclipses with a 20mm eyepiece.

Attempts to use an Orion Shorty-Plus 2x Barlow were disappointing. Dim and fuzzy was the best description even with the 32mm Plossls. Bright sunlight might have helped but all my targets were north facing under a resolutely, overcast sky.

The Orion's optical nose-piece would have shortened the distance and resulting magnification. But the thread size was much greater than the T-S binoviewer body with its own 1.25" nose-piece removed.

My 45° Baader erect image diagonal used up too much light path, in combination with the binoviewer, to allow its use. Which is a shame because it has a nice compression band eyepiece holder. Which provided a much better grip on the binoviewer's nose piece. It would require the telescope's main tube was physically shortened. Or a Barlow lens used to gain some path length.

I have a T-S 1.6x glass path correcter with Barlow in the post. Due to the distance to the eyepiece the resulting power will lie between 2.6x and 2.8x. So a 32mm EP will effectively become a 12mm. Whether the PST filter stack adds further power, due to path length, is still an unknown. More on this later.

The S-T GPC+Barlow duly arrived in the post. Another utterly wasted opportunity! Firstly, it is smaller in outside diameter than the 1.25" fitting. Had it been the same size it would have provided valuable support for times when the binoviewer cannot be pushed right into a fitting.

Secondly, the S-T binoviewer has an undersized body thread for the nose piece. Imagine if they had the imagination and daring to have fitted a standard filter thread in the body. Now anything and everything will fit the body.

The empty nose piece can be simply unscrewed and the GPC or Barlow[s] with 1.25" OD fitted directly to the body. Instead of which the daft GPC will not fit into a standard 1.25 star diagonal! How crazy is that! Nor will it fit into the blind end of the PST eyepiece holder! Now what?!!?

How utterly futile! They chose a non-standard, undersized thread for the body which cripples all the huge potential had it been a standard 1.25" filter thread. Argh!! Ooh, it does make you cross. Well me, anyway.

Click on any image for an enlargement.

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Going H-alpha: T-S Binoviewer first review.

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Having been advised to get a binoviewer for solar observation I did my homework. I chose the Teleskop-Service model rather than the Revelation simply because it has clamping bands via knurled rings. I am always misplacing thumbscrews. Not to mention the cosmetic damage they do!

On arrival, in its neat, but undersized,  aluminium protective case, the T-S binoviewer seemed sturdy and well finished. Unfortunately, the binoviewer's nose-piece presses directly against the back of the metal case. Making the neat sponge insert rather pointless in protecting the prism placement and [hopefully] long term, optical alignment. So, don't ever drop the case! Not unless you modify the protective sponge liner to better protect the nose piece.

The eyepiece clamping rings were nicely weighted for friction but the "diopter" rings were much stiffer. Making adjustment a bit of a chore. I have considerable finger strength from constant lifting, so it's not that. The visible optical coatings were pale green.

Of course the sun promptly disappeared behind a thick overcast and remained that way for days. Not even the occasional clearing at night to try the new toy on the Moon or planets. 

So I turned my attention to terrestrial targets to judge the efficacy of using two eyes rather than one: I plugged the binoviewer into the 1.25" focuser of my Vixen 90m f/11 refractor. Not an ideal choice because the single screw really struggled to hold the binoviewer with two eyepieces to support. I could actually "lift" the load to see that it was still insecure and marking the brand new nose-piece. 

My first target was a multilingual strip of printed packaging with typically small text. Which I fixed upside down to the garden gate @ 25 yards from my viewing spot. A binoviewer does not produce an upright image unless a star diagonal is used.

The results were shockingly good with pairs of 26mm and 32mm Meade 4000 Plossls. Both pairs were secondhand but bought at widely spaced intervals, years apart. By sheer luck I had managed to match the 'Japan' marked 26mm but the 32mm came in two different lengths. One longer and the other the same length as all the 26mm models. Very odd.

Not that it seemed to matter much because the binoviewer offers adjustable [diopter] collars to match eyepieces by making them parfocal. Eyepieces can also be clamped at different depths if desired. Or even individually 'ringed' with plastic pipe off-cuts. To make then automatically rest at the correct depth in the binoviewer's eyepiece holders.

Staring at rusty, cross-head screws in the garden gate became an interesting new hobby at 31x & 38x. The detail was shockingly good in "stereo" despite the overcast sky. With an incredible sense of clarity. Reading small [2mm] print was really too easy using both eyes at this distance and power. More difficult using only one eye. I had no problem at all merging the L&R images. All very satisfying so far. With absolutely no sense of eye strain from misalignment. 

Then I moved onto looking across a diagonal of the garden to increase the range to my next target. It was impossible to use the full garden width due to intervening trees. But 40 yards was still better than only 25 to test visual acuity. Again I was able to easily read the fine text and could still see the punctuation marks without much effort at 38x with the 26mm Mead eyepieces in place.

Click on any image for an enlargement.

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Going H-alpha: Better but not enough.

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Monday: Constant sunshine with light winds. Back out there again with a much improved tail end thanks to the internal support ring. I can see several prominences including a nicely detailed arch. A single dark streak near the limb is very low contrast. I still don't think I have the H-alpha telescope optimized.

I am getting thermal effects on the limb from the roof and chimney which are directly to my south. I should take the telescope up onto the observatory platform to check if that helps. The problem is lifting the heavy Fullerscope's MkIV mounting let alone its massive, welded steel pier. Probably best to put the MkIV on the pyramid pier for isolation. I'll have to rig up my chain winch.

Instead of putting the MkIV mounting up there I decided to lift my massive DIY/ATM Goto [GEM] mounting. There followed the usual struggle to set up two ladders on the platform. I used a massive, square steel tube resting on the pier and dome base rail for the first lift. Once the mounting was safely onto the platform I had to lift the chain hoist up to the peak of the opposing ladders from yet another ladder. My habit of adding ratchet strap "safety guy lines" for the ladders was repeated.

Later I fitted the 6" f/8 [with the D-ERF in place and stopped down to 120mm] to the big mounting  and tried it on the distant woods. At 450 yard I could have seen a fly on a bud on a twig. At 1200 yards I could clearly see each individual twig on the tops of the distant trees. This is the first time I have had such distant views all thanks to the raised platform. This was with a 35mm Meade 4000 Plossl in the 2" star diagonal for 37.5x.

All in all, it takes a coupe of hours from starting to having the big mounting safely bolted onto the pier. I was aching and tired by the time I'd finished. Just lifting the builder's step ladders bodily up to the platform is very hard work. Then they have to be moved around, tied together and finally brought upright.

Now I need a proper weather proof cover for the big mounting. The huge, 275 liter garden waste bags I bought in a supermarket are wearing thin from constant exposure. Nothing else is remotely big enough to safely cover the mounting. I keep thinking about pond liner as a tough, long lasting cover. Welding one into a bag shape would be perfect.

I bought some cheap tarpaulins to temporarily cover the observatory walls. They just happened to be close to the correct size for two panels each. This gave me a better idea of the size of the structure and its likely appearance. Plus, it would give me some shelter from the cold winter winds if I want to observe.

It feels quite roomy inside the 3m, 10' octagon. Black inside and dull green outside are the ideal colours. I still need to add some 2"x 4" timber, horizontal  struts just below and just above observatory floor level to safely fix the plywood panels later on. The image shows the tarpaulins now in place. I went round after this stapling the edges to tidy things up.  It can still rain in from the top down through the observatory floor but it all helps to keep the timber structure fairly dry. I put the folding chair in the doorway to give some sense of scale.

Click on any image for an enlargement.

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Going H-alpha: Improvements.

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Sunday started at 23F, -5C with bright sunshine but more 40+mph gales. I have been out there for an hour now, just trying to improve the view as more and more cloud comes over. I connected the synchronous motor drive for RA to save searching for the sun between adjustments. There is a prominence at my 3 o'clock and a small black and white spot near the lower limb. It all went downhill from there.

After convincing myself that a PST's etalon Barlow lens cannot produce parallel light with any other than an f/10 objective I did a quick drawing. It is obvious that it can do so because it rejects all outlying [converging] beams from a "faster" lens than f/10.

Placing the -20cm focal length, negative lens 20cm inside focus produces parallel light for the etalon regardless of the "speed" [f/ratio] of an objective. It simply ignores all greater angles of convergence. Only those contained within an f/10 converging beam of the same diameter as its own aperture can pass. The negative lens will effectively "stop down" any objective lens until the f/10 condition is reached. So my own 150mm f/8 objective becomes a 120mm f/10. If I demand a 6" aperture H-alpha telescope then I must find a 6" f/10 objective.

I hope the image makes this clear. Sunlight shines upon the negative lens as it converges from the entire objective. But cannot pass through the small aperture of the etalon group unless it lies inside an f/10 cone. Parallel light passes through the etalon and emerges as H-alpha light in the deep red. It is then re-converged at the same f/10 angle as before, by the matching, 20cm focal length, positive lens which lies just behind the etalon. I have not show the re-convergence for simplicity. The actual apertures involved are only put there for clarity. A 4" f/10 is a popular telescope for H-alpha modification. An 8" f/5 would be an extreme example but the drawing shows how much of the extra aperture is simply wasted. All the extra light it focuses cannot reach beyond the etalon/lens group. 

Despite lots of sunshine, today, I never enjoyed such sharp images as I have had before. Surface texture was indistinct and the one, complex prominence a struggle to focus. Later I returned to the 1.25" star diagonal but things did not improve dramatically. Perhaps the sky [or seeing] was hiding all the missing detail? The day finished with snow flurries and 29F. Tomorrow promises to be quieter [but not remotely still] with yet more sunshine. I shall battle on making adjustments as they occur to me.

I discovered an easy way to adjust the angle of the D-ERF filter on its original baffle. I removed the entire tail assembly and gave the baffle a poke up the bum with a sharp stick! A precision sharp stick, of course.

My handheld snaps at the eyepiece were horribly overexposed! Too much contrast for the camera to cope. It's too cold to break out the laptop and Celestron camera. All the cables would freeze solid. 

Sunday steadily clearing to sunshine and 25mph gusts @ 0C. Carefully re-measured the focus point through the D-ERF. Made it nearer 27cm rather than the earlier 26cm. Brought the WO 60mm extension back into play before the etalon and was rewarded with much better images than yesterday.

I really need to fix  the first extension properly to stop it wobbling up and down with the weight of all the extra 'junk' dangling off it. An aluminium backplate would help but would have to be laminated from 10mm plate. I just don't have anything thick enough and wide enough in my dwindling scrap collection to do it one piece. Nor do I have a shallow enough focuser to hold it firmly in place. A brass flange and extension tube would make good sense to help to balance the nose heavy OTA. It would need a decent clamp for the 2" AOK etalon adapter spigot.

I chose instead to turn a hefty alloy ring in the lathe to go inside the temporary plywood adapter. This fully supports the 2" spigot of the WO extender so there is no more sag. I'll replace the plywood with aluminium soon.

Now I know I'm on the right track I can turn my attention to the D-ERF tilt. I seem to be getting some flooding of the image with an asymmetric red blush. Which meant I could tilt my own view through the eyepiece to darken the background behind a prominence. Previously the looseness of the optical system meant it was difficult to be sure what was happening. With the whole set up firmly held I can narrow down the optical alignment of the D-ERF. Just to see if it helps or hinders clarity. A small tilt is desirable to avoid rings forming but the optimum degree of tilt is still an unknown.

Monday: Constant sunshine with light winds. Back out there again with a much improved tail end thanks to the internal support ring. I can see several prominences including a nice, detailed arch. A single dark streak near the limb is very low contrast. I sill don't think I have the H-alpha telescope optimized.

I am getting thermal effects on the limb from the roof and chimney which are directly to my south. I should take the telescope up onto the observatory platform to check if that helps. The problem is lifting the heavy Fullerscope's MkIV mounting let alone its massive, welded steel pier. Probably best to put the MkIV on the pyramid pier for isolation. I'll have to rig up my winch.

Instead of putting the MkIV mounting up there I decided to lift my massive DIY/ATM Goto [GEM] mounting. There followed the usual struggle to set up two ladders on the platform. I used a massive, square steel tube resting on the pier and dome base rail for the first lift. Once the mounting was safely onto the platform I had to lift the chain hoist up to the peak of the opposing ladders from yet another ladder. My habit of adding ratchet strap "guy lines" for the ladders was repeated.

All in all, it takes a coupe of hours from starting to having the big mounting safely bolted onto the pier. I was aching and tired by the time I'd finished. Just lifting the builder's step ladders bodily up to the platform is very hard work. The they have to be moved around, tied together and finally brought upright. Now I need a proper weather proof cover for the big mounting. The huge, garden waste bags I bought in a supermarket are wearing thin from constant exposure. Nothing else is remotely big enough to safely cover the mounting. I keep thinking about pond liner as a tough, long lasting cover. Welding one into a bag shape would be perfect.

Click on any image for an enlargement.

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Going H-alpha: Back focus adjustment [again!]

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Fleeting sunshine during a 45mph gale found me outside again checking the solar image in H-alpha. I had bored the plywood adapter ring deeper to see how that affected things. It was marginally sharper once I had refocused by sliding the Cemax 12mm in the PST's push fit holder. The latest image of the H-alpha set up is shown alongside at focus. 205mm back focus seems rather short compared with the recommended 225mm from the tail edge of the etalon tuning band.

There were three nice prominences at my 8 o'clock in the field of view. Two perpendicular jets and an arch leaning towards them. Surface detail was slightly improved during brief moments of clarity between heavy clouds. There is a red wash to the background on one side of the solar image only.

The wind was so strong, despite there being two [bare] 10' hedges between myself and the easterly gales, that was I being pushed off my beer crate hop-up. It clouded over much more heavily after lunch and the blue gaps were now no more.

If only I could get some steady sunshine I could check the position of the etalon tuning band relative to the refractor's focus. It really needs a steel rule and a board to measure the distance of the sharpest red focus from the plywood backplate. This would be far more accurate than trying to measure from some arbitrary point on the thick, objective lens.

A black surface [emery paper?] on which to focus the sun's image is best IMO. Because the intense brightness of the sun's image even with the D-ERF in place completely blinds one to the sharpest image.

The briefest of clearing in the thick cloud allowed me to double check the precise focal distance from the backplate. 26cm exactly, with or without scudding cloud. So I need to aim for 6cm to bring the PST etalon 20cm inside focus. I had no choice but to swap out the WO extender to the 40mm x 2" extender. Drilling 120° apart and tapping the holes 5mm for extra thumbscrews should provide some extra stability. The actual focal point for the eyepiece remains completely unknown as I waited in vain for one of the tiny blue holes in the cloud to cross the sun. It even started snowing to add to the misery of standing in a gale at -1C, 30F. Talk about obsessive behaviour!The moment I returned indoors for lunch there were a few seconds of watery sunshine. Grr!

Two more freezing hours chasing gaps in clouds in a bitterly cold gale. With the etalon now fixed at the correct distance the EP is in focus just as it falls out of the PST eyepiece holder. Grr. A quick check and I found the 2" star diagonal would now work instead of the 1.25". Tomorrow is promised to be sunny yet again.

If I can get a few seconds of real sunshine I can confirm if any progress has been made in image quality. Not to mention where the EP will reach focus with the larger star diagonal in place.  The latest image shows the eyepiece at focus using the 2" star diagonal. I'm back to using the bored out [plain aluminium] adapter to hold the ITF/BF filter stack.

Click on any image for an enlargement.

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Going H-alpha. Back focus adjustment.

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The etalon position changes the back focus [beyond the etalon] much like a Barlow lens. So I need to get the etalon positioned 20cm inside focus. Only then will the post-etalon focus lie in the correct position of 225mm beyond the back of the knurled rubber band.

To that end I have obtained an extension of 18mm via T2 threaded parts: The image [left] show the assembled parts and [right] the components laid out.

The 2" adapter has a T2 male thread on top. This accepts the T2 to 1.25" adapter.

I removed a standard 2" to 1.25" adapter with its single clamping screw. But gained a high quality 1.25" compression band fitting with two seriously dimensioned, thumb screws. I also bought a locking ring to conceal the unwanted T2 male thread on the 1.25" fitting for better neatness.

The next image shows the assembled etalon with AOK etalon to 2" adapters. The 40mm x 2" extension tube is probably too long. The TS 2" adapter fits into the 40mm extension.

The new 1.25" compression band firmly holds the 1.25" spigot from the 1.25" star diagonal. The PST filter stack and EP holder is screwed directly into the top of the star diagonal.

The new parts provide a very firm and inflexible support for the heavily loaded star diagonal. Where the earlier 2" to 1.25" adapter, very clearly, did not. The whole star diagonal and filter stack would literally rock up and down.

Until I get some sunshine I have no idea how long the new back focus will be. I'm guessing that  I must discard the 40mm x 2" extension. The TS T2 parts [alone] offer only 20mm extension but T2 spacers are readily available in numerous widths once I am in the ballpark on back focus. There are even adjustable, male threaded components which can act like a simple helical focuser. Which can then be locked, at the desired length, with a female threaded  ring.

I started turning a 2" x 20mm long brass extender in the lathe. Then suddenly realised that it was physically impossible. The 2" OD spigot of the extender must always fit into another 2" bore fitting of matching length. While the 2" bore tubular section of the extender must be deep enough to hold the full length of the following spigot. It is thus impossible to make any 2" to 2" tubular extender shorter than the spigot length plus the minimum safe shoulder depth [X] of material to join the two sections of pipe.

A reducing adapter [from 2" to 1.25"] can certainly be made much shorter. But not a 2" to 2" extender. Attempting to shorten the spigot, or the tubular section, merely weakens the connection though lack of adequate support for the fittings which come before or after. Which is partly to blame for the poor support offered by most 2" to 1.25" adapters. Ideally they should be made to the full depth of the 2" Ø tube in which they are clamped. Though this would add considerably to the weight unless they were bored out to be much thinner. A compression band fitting is a huge advantage in this context. Rather than the single, miserable, little thumbscrew usually offered in cheaper fittings.

Click on any image for an enlargement.

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Going H-alpha: Against the odds.

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I wish I could report an update by now but the weather has been horribly cold, cloudy and very windy simultaneously. It was 23F, -5C in my workshop and I'd rather not let my breath condense all over everything. Just handling metals even in grippy, industrial gloves is unpleasant at these temperatures. Just putting the gloves on in the first place takes some stoicism if it quickly leads to fingers aching with cold. I do have a variety of industrial gloves but none is really meant for these low temperatures.

Friday and a balmy 28F, -2C in the shed meant I could brave the cold to re-position the D-ERF and other baffles. D-ERF is now better squared on at 27cm from the objective end of the tube. The largest baffle is now just inside the tube to stop down the 150mm f/8 objective to 120mm @ f/10. The sky promptly turned dark and cloudy to celebrate the moment after fleeting sunshine earlier in the day.

Sunday: It has risen to 26F, -3C with a roaring gale as I prepare the H-alpha solar telescope for fine adjustment. I quickly checked the focus with just the D-ERF in the system. The sharpest solar image seems to be at 27.5cm from the plywood backplate. Whoops! I thought it was much shorter than that. It's lucky I now have a good range of extenders!

In the end the WO 60mm extension was the perfect length to house the front AOK-etalon adapter. I took a handheld snap at the Cemax 12mm and "processed" it in PhotoFiltre7.

Viewing straight through I had seen a large prominence in the form of a mu and another looking like a pair of opposing brackets. The fuzzy mess on the limb [right] was the mu. I seem to have captured some surface detail despite my best efforts.

When I attached the 1.25" star diagonal I needed a rather shallow extension. A 2" to 1.25" adapter, 22mm long would probably do it. See image at the top of the page. Bright sunshine soon turned to dense overcast before I could explore best tuning and focus. Hours of poring over astro sales websites produced nothing useful. I shall have to make my own on the lathe.

Or not. T2 fittings are not exactly cheap but will solve my optical, path length problems. While leaving me with a whole range of potential options. Order placed. Pictures when they arrive.

Tuesday: Bright sunshine 43F but misty. Further experimentation shows the "straight through" distance is 216mm from the leading edge of the PST etalon sleeve. The 1.25" star diagonal needs 22mm withdrawl for best focus when the 80mm extension tube is removed. Suggesting the star diagonal has an optical path length of 58mm when the TF/BF filter stack is screwed into it directly. [80-22mm.]

I was able to see several prominences quite clearly using a variety of eyepieces. Surface texture was visible in a ring with a blank center. A red blush lay off to one side of the sun's mage. Possibly misalignment of the D-ERF? My attempts at handheld 'snaps' today were no more successful than last time.  

Further advice from an expert suggests my etalon is too far out. The straight-through, back focus REAR of the etalon adjustment band should be 200mm. I thought I was working from the front! So the rubber band width has to be added to the measured length. Unfortunately I cannot measure the true back focus without sunshine. None is forecast for the next week. The WO 60mm extender has serious clamping for the AOK etalon adapter. So I 'd like to retain this even if I really need a shorter fitting. Time to start counter-boring the plywood ring.

I could fix another plywood ring on the back to maintain hole depth and stability. The sloping, security cutaway on the telescope side of the WO extender doesn't help stability in a parallel hole. Nor, probably, when a compression band fitting is used to hold it in place. I hope to turn a solid aluminium backplate when I have finalized the dimensions. It is premature to start now. Hence the plywood ring. Five minutes was enough to counter-bore the 2" central hole for the WO extension to sink 1cm into the surface of the plywood ring. The etalon band is now exactly 100cm from the ridge between the objective cell and dewshield. I removed the cell and measured the depth to the back of the objective to be sure.

Click on any image for an enlargement. 

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