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Monday 3rd 40F, overcast with rain. Back to turning the new, light alloy, backplate/tailpiece.
The finished disk weighs quite a lot but must balance the heavy D-ERF filter and holder. The 160mm D-ERF comes in the form of a really substantial blank. Fully 10mm thick compared to my original 90mm, internal D-ERF at only 5mm thick! [Left] A matter of scale. 7" f/12 and 6" f/10 at the same distance. One is almost too difficult to lift, even without its heavy objective. The other seems almost "dinky" and effortless to move about in comparison. Yet a 6" would be considered a large telescope by most. Many baulk at the difficulty of mounting a 6" f/8. The tube of the f/10 is a foot longer and over 3/4" greater in diameter than the f/8.
With my shortest 35mm extension the PST etalon is now 200 mm inside focus. I added the clamping ring from the previous solar telescope and screwed it on from the back/inside. The nuts shown are unnecessary but lift the extender just enough. To bring the etalon to the correct position minus a millimeter or two. I may use the slightly taller "Nyloc" nuts to act as a reference. Or, add a packing ring under the clamping ring.
I have to add another 2" IR filter to add in front of the etalon. A Beloptik KG3 UV/IR cut was recommended for thermal protection of the PST etalon. That will push the nosepiece out by the thickness of the filter ring. I can't put it anywhere else. There is no other 2" thread in front of the etalon. My 35mm extension doesn't have a filter thread. Perhaps I had better find one with a thread? The Baader Click-Lock series has a 37mm x 2" fit. Now I need to drill in from the side and tap the holes to fix the tailpiece securely in place in the main tube. [Job done with M4 screws.]
The PST filter stack stack now feels absolutely solid compared with the [longer] previous [GPC] version. So I shan't need a truss support for the tail end of the filter stack after all.
I have heard back from Telescopes Express. They hope to post the replacement, full aperture, filter holder today or in the next few days. The D-ERF and its holder are the last details for completion of my new, 6" f/10, H-alpha telescope. Apart from some internal baffles and a spot of matt black paint inside the main tube.
Tuesday 4th 37F and it is sunny and I don't have a telescope ready for use! The 7" is in pieces after dismantling the folded version. The old 6" is in pieces from working on the new 6". No D-ERF or baffles fitted yet. Grr? It was the same last night. After a heavily overcast day it cleared in the evening. A half moon, almost overhead and a brilliant Venus to the SW. No usable telescope!
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