Dome building: Rest day, going Solar H-alpha.

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Tuesday: I had a rest from dome building and played at Solar H-alpha with my 6" refractor conversion. I was struggling with balancing the 6" even with only one 5kg counterweight. So added the home made, sliding brass balance weights from my home made 7" refractor. I bolted the sliding weight tube, with newly made aluminium brackets, to the side of the 30" long saddle. This helped to balance the relatively lightweight, 6" refractor without having to reduce the mounting's counterweight.

I had crystal clear solar images, with very even surface detail, when I started viewing at 11.30am but the seeing slowly softened throughout the warm and sunny day. It eventually reached 74F or 23C. I am still unable to use my binoviewer even with the 1.6x T-S GPC. It just will not reach focus with a star diagonal fitted. No problem viewing "straight through" except for the near impossibility of tilting my head 50° backwards to use the binoviewer.

I also discovered that the thread on the T-S star diagonal is the same as on the no name diagonal. So the PST filter stack will screw securely in place of the eyepiece holder. The optical path length on the T-S star diagonals is longer than the no name variety.

I can't use the PST eyepiece holder with the undersized T-S GPC when fitted to the binoviewer nose. So I shall have to add two more thumbscrews to get a proper grip. I wonder whether there is enough meat [wall thickness] to cut a groove for a compression band to fit in the PST eyepiece holder? The PST's BF5 [5mm blocking filter] is fitted in the base of its eyepiece holder. So it is probably impossible to add the BF to a star diagonal without making an internal disk to screw into the T-S eyepiece holder. That's the only way to get the compression band fitting I need for the T-S GPC.

Wednesday: Further experimentation proved that I could focus the 26mm Plossls in the binoviewer + 1.6x GPC + T-S 1.25" 90° star diagonal. It required that I push the 2" nose of the Etalon adapter directly into the tailpiece. This doesn't make any sense from a geometric point of view where the PST etalon ideally wants to be 200 mm inside focus. I may have to invest in the other 2.6x T-S GPC which claims zero added path length. Though at the expense of increased magnification.

Thursday: The images show the new, aluminium tailpiece disk I turned in the lathe. I put a step in it so it wouldn't vanish inside. It took ages to make from a roughly cut piece of 10mm plate. A ring is bored to 2" to provide solid support inside the new disk.  Three radial 4mm screws hold the 2" extender.

I could see the whole solar disk but it wasn't as clear as the single 18mm PST Cemax EP. I'm not keen on the Meade 4000 26mm Plossls for binoviewing because of the large eye clearance making it difficult to hold my head still enough at a distance.

Friday: I drilled two more holes in the PST eyepiece holder and tapped them for 4mm thumbscrews. I'm still trying to get the binoviewer focused but don't have enough back focus. Big clumps of Cumulus are making it a tediously slow trial and mostly, error.

Finally, I had focus with the star diagonal, binoviewer and GPC in place. Note how short  is the distance between the etalon and star diagonal. [Arrowed] Just room for a 15mm deep 2">1.25" adapter. The connection between the two components could be achieved by shortening an AOK Swiss PST rear etalon adapter. Instead of which I have ordered a 2.6x GPC and hope that will solve the lack of back focus. T-S claim a 105mm compensation for this GPC. Which should effectively neutralize the focus shortening effect of the binoviewer.

Sunday: I dragged the H-alpha telescope up to the big mounting on the platform. The AWR IH2 handset needed somewhere to rest. Somewhere it would be handy but out of the sunshine. So I hung it from the north side of the sloping plywood pier cladding. Two roofing screws, some washers, some 'pex' tubing for spacing and padding is a bit crude. Very good it was too. As it was within easy reach of the eyepiece of the 6" as I searched for sunspots and prominences. I swear I remember seeing a neat, aluminium hook for the IH2 on the AWR website but can't find it now. The AWR drives have been going all day keeping the Sun in the field of view. Only the power supply warmed up. The motors and electronics remained cool. 

Click on any image for an enlargement.

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