Are we having fun yet?

Astrophotography: share your photos & discuss techniques
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Pete
Astro Day Coordinator
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Joined: Fri Jun 13, 2003 9:03 pm

Are we having fun yet?

Unread post by Pete »

Sunday, 29 Nov 2020

Took 2 more flat fields this afternoon. The first a daylight T shirt flat and later a 20 frame series of 2s twilight T shirt flats. Although the forecast predicts clouds coming in they held off until around 19:00 allowing time to experiment.
IC 1805 annotated.jpg
IC 1805 annotated.jpg (936.3 KiB) Viewed 705 times

ASI2600 on 14” at f/8.6, 4X binning, 14 X 5 min, -15C, 200g, 2s guiding. Twilight flat used.

Still having major problems with vignetting and banding. Individual frames are heavily crosshatched – extreme banding. Stacking them in IP doesn’t help. The above is the live stacked image in FITs format that could be processed in IP.

The above is a cropped image. Darks and flats were applied during the live stack and the section of the image cropped looks OK. But the uncropped version has heavy vignetting on the corners. Strangely, the left hand corners are black and the right hand corners are white.

It’s 43°F. In at 18:42hrs. Shut down by cloud.

Conclusions and lessons learned.

The vignetting didn’t happen before the focal reducer was inserted into the optical path. And would probably be solved by removing it. Flats and darks are working in the central part of the image. But the focal reducer also functions as a field flattener and it has eliminated coma.

Consequently I’ll continue to work on this setup. Two possibilities come to mind. The first is to follow an online hint regarding longer exposure flats and the second an online hint regarding light leakage. Want to rule out all known possibilities before once again asking for help on the forums.
Who would have thought that OSC would be this complicated?
Pete P.
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menardre
Vice President
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Joined: Tue Jan 17, 2012 6:09 pm

Re: Are we having fun yet?

Unread post by menardre »

Pete

That is a really outstanding image of the Heart Nebula. Great color.

Your comment regarding about complicated OSC imaging - remember, you are starting with the absolute hardest set-up. A 14in scope and a camera with relatively small pixels really makes imaging difficult.... but the results can be fantastic (as seen in your image).

Roger
Roger M.
Celestron CPC1100 EDGE, Stellarvue 130T refractor dual mounted on iOptron CEM120 on permanent pier mounted in Observatory. Imaging camera ZWO ASI2600 OSC, guide camera Lodestar or ZWO ASI290MM.
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