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NGC 7635, Bubble Nebula, LRGB, 96% waning moon

Posted: Thu Sep 19, 2019 3:36 pm
by turfpit
A first serious attempt to get to grips with imaging using LRGB filters. The conditions were not ideal with NGC 7635 on one side of a tree and the moon on the other. LRGB colour balancing using ratios has been tested without wasting good conditions.

The RGB ratio used was 1.7 : 1 : 1.5. RGB was bin 2x2 with 60s exposures. L was bin 1x1 with 90s exposures. The ratios were derived based on the work done by Brian Morgan (@oopfan) at https://u235.herokuapp.com/#color-balance-instructions.

NGC7635-LRGB.jpg
NGC7635-LRGB.jpg (192.46 KiB) Viewed 476 times

Celestron AVX mount, Vixen 81sd refractor, Altair 1.0x flattener. Atik 314E CCD camera.
Sharpcap 3.2 with Atik ASCOM drivers.
Unguided, focus with Bahtinov Mask, Teleskop LRGB filters & Teleskop filter drawer.
Integration time 2.2h; L bin 1x1 50x90s; RGB bin 2x2, 60s; RGB 24:14:22; 100 bias, 100 flats @ bin 1x1 & bin 2x2; 30 darks @ bin 1x1 & bin 2x2.
Imaging order was R > G > B > L for capture east of the meridian (L > B > G > R for west of the meridian).
Total captured data = 1.1Gb.
Calibration, registration, stacking and RGB Composition were carried out with Siril. Final (minimal) processing used Gimp.

It will be interesting to revisit this target when there is no moon. While I wait for that I may try for an SII-Ha-OIII capture.

Dave

Re: NGC 7635, Bubble Nebula, LRGB, 96% waning moon

Posted: Thu Sep 19, 2019 3:45 pm
by turfpit
Some screens captured during the LRGB imaging session. Note the use of Display Histogram Stretch to be able to see what was being captured and the use of Zoom=200% plus Display Histogram Stretch to obtain a detailed view of the diffraction pattern for focus. Navi was the star used for focusing - medium brightness and close proximity to the Bubble Nebula.

focus-with-bahtinov-mask.JPG
focus-with-bahtinov-mask.JPG (60.32 KiB) Viewed 475 times

red-filter-capture.JPG
red-filter-capture.JPG (60.19 KiB) Viewed 475 times

red-filter-flats.JPG
red-filter-flats.JPG (46.75 KiB) Viewed 475 times

green-filter-capture.JPG
green-filter-capture.JPG (54.36 KiB) Viewed 475 times

blue-filter-capture.JPG
blue-filter-capture.JPG (62.47 KiB) Viewed 475 times

luminance-filter-capture.JPG
luminance-filter-capture.JPG (62.64 KiB) Viewed 475 times

Dave

Re: NGC 7635, Bubble Nebula, LRGB, 96% waning moon

Posted: Thu Sep 19, 2019 6:22 pm
by nexusjeep
Hi Dave,
Nice image in difficult conditions, hopefully going to get out tonight to capture something.

Cheers
Nick

Re: NGC 7635, Bubble Nebula, LRGB, 96% waning moon

Posted: Thu Sep 19, 2019 6:58 pm
by turfpit
Cheers Nick. I am giving narrow band filters a go tonight.

Dave