Revisiting M81/M82

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Pete
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Joined: Fri Jun 13, 2003 9:03 pm

Revisiting M81/M82

Unread post by Pete »

24 Apr 2024

While I’d planned to work on the scope/camera setup tonight the sky unexpectedly cleared and it became an observing night. Disconnected the guide camera to scope guide port cable. Removed the LP filter from the refractor optical train, and ran appropriate flats.

It’s 54°F and there’s a strong breeze – about 20 mph. With the moon down it’s delightfully dark. Slewed to M81/82. The full moon will be down for another hour or so and the galaxies are far removed.
M81 M82 s.jpg
M81 M82 s.jpg (1.24 MiB) Viewed 35371 times
Messier 81 / Messier 82
24 Apr 2024 20:35 – 23:32 EDT
54 X 3 min, unbinned, -15°C cooling, 200 gain, 1 Hz guide rate
Explore Scientific 102mm refractor with ASI2600MC-P camera LP filter not used

6 out of 60 frames were discarded, 5 from airplane/satellite passes and one where the scope appeared to have been bumped. With PHD2 set for N declination correction only guiding went beautifully. Guiding is through ASCOM and hence there was no need to recalibrate guiding.

Results aren’t quite as sharp as the 38 X 3 min 120 gain image taken with the same setup with the LP filter on back in March 2022. It was calm that night. And even with a bit shorter exposure and lower gain and the filter the older image has brightness and resolution. And stars are sharp in both.

Conclusions & lessons learned:

I think that the lower resolution was due to wind. Didn’t stop to verify seeing but it’s either that or poor focus. Strangely when focusing the multi-star FWHM was only 4.3 pixels, and that was with the wind. A puzzlement for sure.

The PHD2 problem seems to have been solved, and I’m relieved that it’s guiding through ASCOM rather than the direct camera to scope connection.
Pete P.
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menardre
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Re: Revisiting M81/M82

Unread post by menardre »

Pete

Looks like some light intrusion in upper left and right .... I know it was full Moon, but Ursa Major should be far enough away.

Your stars look really good so I am not sure why the galaxies are not as crisp as they could be. M81 actually looks pretty good so maybe it is the light intrusion that is impacting M82.

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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Pete
Astro Day Coordinator
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Re: Revisiting M81/M82

Unread post by Pete »

I agree with the light intrusion situation. Much worse last night when I didn't turn the brilliant monitor off.
Pete P.
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