M81 (Don Walters)

Celestial hemisphere: Northern · Constellation: Ursa Major (UMa) · Contains: Bode's nebulae · M 81 · NGC 3031

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M81

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M81

Shot over 4 nights in April, over 11 hours integration of LRGB.

For this target (and another before it) I was trying to shoot as close to the noise floor as I could. For each shot, I would make sure there was just a bit of clearance between the hump in the histogram and the left wall. Just really kind of testing to see what I could get away with. I calculated that 10xRN^2 would be about 320 in 16-bit. So I started shooting subs and getting medians of 360 (red) to 630 (blue). So I was just barely above the floor.

Also trying to get more use out of my ASI178. Its a neat little camera that is no longer available anymore, except on the used market.

As with all my RGB efforts, the background was pretty hard to tame, so it really limits how far I can stretch. Otherwise, I could have brought out the galaxy arms a bit more. I was using pretty aggressive dithering, but it didn't seem to buy me very much.

PI Processing:

Crop and DBE to each LRGB master

LinearFit (to Lum)

CanonBandingReduction on R and L because these were so close to the noise floor. (I probably needed to expose a bit longer).

LRGB Combination

BackgroundNeutalization

PhotometricColorCalibration

MLT (noise reduction)

HT x2

ACDNR x2

HT (clip the blacks)

Curves (desat the background)

Curves (saturate galaxy/stars)

Resample down 1/2

Original
Final
B

B

Description: Used PhotometricColorCalibration which seemed to give me a lot more red.

Uploaded: ...

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Status	Basic success
Started	...
Astrometry.net job	2679665
PixInsight job	n/a
PixInsight queue size	n/a
PixInsight stage	n/a

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M81

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Image Index:

Contribution Index (beta):

M81

M81

Equipment

Acquisition details

Description

Comments

Revisions

B

Sky plot

Histogram

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