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Except
that nobody makes a 70mm extension. So, for the moment, I'm using a
60mm extension with 10mm of the etalon spigot visible. Had I chopped
only 10mm from the main tube I'd be golden. Ah, the wisdom of perfect
hindsight! The only time there was any real sunshine, between the heavy clouds, it rained. So I'm waiting for this afternoon's promised sunny periods to see if using the correct etalon distance actually improves matters.
I can't be certain but I think I've been using too long an extension until now. Probably putting the etalon at 180mm from the focus instead of the desired 200mm. I was actually doing the right thing by chopping the main tube but overshot by 10mm. When I only needed to gain 10mm of inward focus. I can experiment with reducing the 10mm of spigot overhang to see if it helps the image quality.
I'm keen to see if the PST "sweet spot" has
changed with the correct geometry. It was a nuisance having to
constantly move the sun's image around the "O-ring" of increased
sharpness. The best eyepiece focus is longer than before. Because I'm
having to use a bit of extension on the 2" spigot of the short helical
focuser and a bit less on the eyepiece barrel. This could be improved by
adding a T2 extension. As I enjoy lunch the sun keeps coming out full strength for a few moments. It's going to be a long afternoon. As soon as I was back out to the observatory it started raining hard! Then hailed. It was lucky I took my laptop with me so I can waffle during heavy showers.
15.00pm and still no sun!
15.35 and still waiting for long streams of cloud to pass. Large patches of blue overhead. Even when the fast moving lower cloud clears there is often higher cloud. I did a manual flip and centered and synced briefly on the sun. So the drives can keep it within sight in case of a sudden clearing. It saves time not having to search for the disk. You need the patience of a saint with astronomy!
15.40pm 48/43F [Out/in] cooler in the wind through the slit. Sun at last! The large dark filament is now just above central in my view of the disk and nicely clear with lighter patches around the base. Quite a tall "C" shaped prom growing at my 10.30. Or about 10.00 on GONG H-a. Best seen at 60x. Still nothing visible in white light +SC. Sun now only 8.5° in altitude. Milky sky low down to SW.
16.10pm Filament still visible but local trees now obscuring the sun.
16.15pm Cold and giving up for today.
Click on any image for an enlargement.
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