Staring at the Sun, 20

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8/30/2010: In the evening, I took the camera out to try some nocturnal imaging. Here's Epsilon Lyrae 1 & 2 through the 5-inch A-P with a 2x barlow (best 40 out of 200 frames, 130ms per frame, 7 frames per second, 8bit):

eps Lyrae

That's cropped but not resized. It looked very much the same on the screen while preparing to capture. I make it 487 pixels center to center of the wide pair which is 204 seconds of arc and that suggests an image scale of 0.42 seconds per pixel. The stars in the closer pairs are a whisker over 2 arc seconds apart (if those really were headlights, they'd be headlights as seen from about 110 miles away). I won't mind if you check my math. 0.42 seconds per 3.75 micron pixel implies an EFL of 1,850mm, so I'm working tonight at F14.6. That's a factor of two or more shy of where I should be for the highest resolution imaging (at least according to the best advice about webcam-style astrophotography). We'll see. Elsewhere in the deep sky: I couldn't even get a smell of M13.

I waited for Jupiter to rise and then to clear the pines in the east. I tried several settings, ranging from 1 ms with 23db of gain to 200ms in an effort to collect some field stars. Only the one prominent belt was plain to see on the screen. A processed series of 300, 1ms exposures reveals more belts, the Great Red Spot rotating off the disk at about the 2 o'clock position, and the shadow of Io just entering the disk on the left:


That may not look like much, but it's so much more than I could see that I still find it promising. Jupiter was only 25° up at the time.


8/31/2010: As the Sun rose, I set up the A-P again and took aim at the fading Moon. Ah, this is going to be fun. I see a new spin-off subsection to The Slow Blog looming (see "Howling at the Moon" for more lunar photography starting this morning). For right now, let's call this solar practice and include a lunar image here.


Look at those craterlets in Clavius! Look at those terraces in Tycho! Just look at that. Not bad for a shot in bright twilight, eh? I used the same set up as for Eps Lyr and Jupiter: A-P 5-inch with a TeleVue 2-inch Barlow. I tried several settings with the Chameleon; this one is 200 frames of 8-bit data, auto-everything, 15 fps, about 20ms per frame. I also tried higher gain and shorter exposures of other areas, but noise can be a problem. A 12-bit AVI of this area shows little or no advantage (at least given my undeveloped lunar processing skills). I used Registax to do a multi-point alignment on the best 30% of frames, wavelets, then in PhotoShop did unsharp masking followed by Focus Magic and curves adjustments.

Today I replaced the set screws on the Lunt that hold the Feathertouch focuser in place. The new screws are stainless steel knurled thumbscrews. To remove the focuser from the solar telescope and put it back in service as a fine focus supplement on the A-P requires only that I loosen those three thumbscrews. This is a suggestion that came from an observer on CloudyNights (complete with McMaster-Carr parts number) to make rotating the Feathertouch for storage easier. I took it one step further and modified the FT adapter to let me casually swap it among multiple scopes. Considering I have a lot of 'scopes and FT modules go for upward of $300 these days, making it easy to share mine among several instruments seems like a few bucks well spent. The FT may be as critical for the best lunar photography as it seems to be for the best solar photography. The difference is that the A-P has a very nice focuser already, albeit a one-speed model.


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                   © 2010, David Cortner