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Contains:  M 81, Bode's nebulae, NGC 3031
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M81 - A Backyard Bode's Galaxy, 


M81 - A Backyard Bode's Galaxy

M81 - A Backyard Bode's Galaxy

Technical card

Resolution: 2877x2850

Dates:March 4, 2019

Frames: 207x180"

Integration: 10.3 hours

Avg. Moon age: 27.60 days

Avg. Moon phase: 4.17% job: 2575568

RA center: 148.896 degrees

DEC center: 69.065 degrees

Pixel scale: 0.520 arcsec/pixel

Orientation: 268.708 degrees

Field radius: 0.293 degrees

Locations: Home Observatory, Snohomish, WA, United States

Data source: Backyard


This is M81. Bode's Galaxy.

We had a stretch of clear nights in early March, 2019 that happened to coincide with very little moonlight, so I wanted to go for a redo of this object. I imaged it last spring from Pixieland Star Party, but the conditions were quite poor. You can find that image in my gallery to see the challenges I faced and the result.

This one was taken over 3 nights, from March 2 through March 4, 2019.

I experimented with a few new techniques in PixInsight, most notably the MureDenoise script. This script is intended to use your camera's measured noise characteristics to apply different kind of noise rejection as the very first processing step after integration. Other noise rejection algorithms are essentially specialized blurring algorithms that, if used in the linear state, can leave artifacts that are very difficult to address in later processing. With MureDenoise, I was able to pretty effectively tame the low level background noise in my camera. I am thoroughly delighted with it. It gave me a very good foundation upon which to do the rest of the processing.

The details for this image are as follows:

Telescope: Celestron EdgeHD 8 @ F/7
Camera: ASI1600MM-cool with 1.25" Astrodon GenII RGB filters
Mount: Astro-Physics AP1100GTO-CP4
Guiding: Starlight Xpress Ultrastar with Teleskop-Express Thin OAG
Capture Software: SGP with PHD2
Processing Software: PixInsight

Capture Details: 68x180r, 72x180g, 67x180b @ Gain 76 & Offset 40

As some additional notes, this is still an object that gives me some trouble with colors. Even though I use PhotometricColorCalibration and get great fit in the graphs, I always get a greenish tint to the galaxy core. Also, I find very few areas of clean, blue color. I've seen other images with substantial blue in the galaxy arms, but I just don't see it in this galaxy.

And finally, the two brightest stars in this image have some tragic halos that are partly a characteristic of the cover glass on the Panasonic sensor in the ASI1600. It does not have an anti-reflective coating and will present a grid of reflections around bright stars. If I push the luminance on this image, I can clearly see the effect. As it happens, I've not pushed the luminance anywhere near as far as it could go, so there's no problem there. But pushing for sufficient color saturation made the issue much more noticeable in the chrominance layer. I'm continuing to consider the best processing fix for it. If you have ideas, let me know.




License: None (All rights reserved)

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M81 - A Backyard Bode's Galaxy,