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Messier 81, 82 and NGC3077


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About this observation
John Hughes
Time of observation
01/03/2020 - 20:20
Messier 81, 82 and Ngc3077
Observing location
North Essex, UK
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Here is my rendition of Messier 81 (Bodes Galaxy), Messier 82 (Cigar Galaxy) and NGC3077 captured across the nights of the 1st, 2nd and 12 March.
The image was taken using my William Optics Z103 refractor, ZWO ASI1600mmPro camera and is made up of 5 separate master images capturing the Luminance, Red, Green and Blue channels as well as emissions in Hydrogen Alpha. Overall this image represents 6.7 hours of exposure time.

William Optics Z103 APO Refractor
ZWO ASI1600mm Pro Cool camera
ZWO Filter Wheel
Sesto Senso Focuser
Pegasus Astro Ultimate Powerbox V2
Skywatcher HEQ6R Pro mount
William Optics 50mm Guidescope
ZWO ASI290mm mini Guide Camera
Filters used;
Chroma LRGB
Chroma Ha 3nm
Captured using Sequence Generator Pro
Processed using PixInsight

L 19 x 120s & 98 x 60s Bin 1x1
R 10 x 60s Bin 2x2
G 10 x 60s Bin 2x2
B 15 x 60s Bin 2x2
Ha 46 x 300s Bin 1x1
Gain/Offset 139/21
Camera Sensor Temperature set at -20 degrees centigrade.

Calibration Frames
50 Dark frames for each exposure/bin setting
50 Flat frames for each filter/night session
50 Dark flats for each filter/night session

I had some issues here with artefacts and also as this was my first attempt at combining LHaRGB the calibration of the lights with flats, darks and dark flats was a challenge. Warren A. Keller, author of Inside PixInsight was very helpful in an earlier question I put out to the PixInsight for Beginners Group on FaceBook and cleared up my confusion over calibration.

Ron Brecher presentation on The Astro Imaging Channel on YouTube helped with a dust mote that wasn’t entirely cleared by my master flat (Pixel Math section “if the pixels are this, do this, or do nothing”). Using this method helped me to slightly raise the brightness of pixels in the offending area leaving the rest of the image untouched.

The artefact? Well, as hard as I tried I couldn’t remove a lightish smudge to the left of Messier 81. I checked on the Astrobin website at other Messier 81 images and thought, “Hmmm, I’m gonna plate solve this before I go any further”. Turned out it was the galaxy PGC28757! So, no adjustment was necessary.

This was very much a challenging project using five filters and the additional complication of imaging across multiple nights though it was well worth the time put in.


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