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NGC 3031 & 3034 Widefield


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AKA M81 & M82 (but made you look ?)

Also featuring NGC 3077 (top right), NGC 2076 (middle left), NGC 2959 & 2961 (Lower left) and numerous other galaxies. 

This is my first attempt at an LRGB image. lots to learn! A work in progress, but having spent all evening processing it I thought I'd share.

Most of the data was captured this week, although a few frames were captured in January. Around 5.5 hours of Lum, and a fairly measly 45mins for each of the colours. I left the scope running all night unattended for the Lum, which was a first and I was amazed it all worked and I woke up to find it nicely parked up with all the frames usable. Transparency on the night i took the colour frames was awful, but I plan to get some more colour when I get chance. All 5 minute subs @ Gain 0.

Not happy with my flats on the colour frames, I ended up with a very uneven background, especially on the red channel, so I've had to dial the red down a bit in the background, hence the colour balance is a bit off. I will have to have another go there.

Overall quite happy with the detail in the galaxies @ 100% zoom, considering my setup isn't a galaxy hunter and my skies are terrible (Bortle 8). The background is quite painfully noisy, I will see if I can improve on that on the next processing attempt. but looks like I'll be stuck shooting LRGB for the next few months until the nebula come back around.

Equipment: Star71, AZ-EQ5, ZWO 1600MC.

Any feedback welcome :)





Edited by SamAndrew
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I like the wide field of view. Very nice.

On my screen (MacBook Pro) the image appears quite green. I ran it through SCNR in PixInsight to reduce green throughout the image and then set the background to R:G:B - 23:23:23 in Photoshop and in my opinion it looks a whole lot better on my screen. Others may have a different view/advice.



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Very nice image. I agree with @Adreneline that the image appears a bit green. In PS there's a plugin called hlvg (hasta la vista green). Or you can bring the histogram for green down a bit. The noise is probably caused by your sky. Bortle 8 needs a lot of integration time.

There are some stacking edges left in your image, causing the uneven background. Maybe some frames were rotated relative to the reference frame. There's really only one way to deal with that if you want to keep all frames, afaIk: crop.

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Hi Sam

Even though I do see the green as well, to get something like that from Bortle 8 is stunning, in my view. Arp's Loop is peeking out faintly. Plus all these galaxies, it's an interesting widefield.

If there are no plugins in PS, one could make a synthetic flat, which would take down the green and vignetting, too.

For reference, here's how I do it:

1) Duplicate image (Image > duplicate), call it flat

2) Filter - noise - Dust and scratches (Radius 100, threshold 0)

3)Clone tool Clone out the brightest areas, and the edges

4) Filter - Gaussian Blur (between 130-250)

5) Curves to darken the flat just a bit (to preserve the brighter areas in your image)

6) Activate main image, then > Image > apply

7) In the box (menu dialog) that pops up, Source > Flat, Blending > Subtract

8)Then you play around with Opacity - lower the no. (for color and brightness), and Offset (bright and dark)

If you have the eyedropper tool engaged (4 sample points in the corners of the image), you can see the effect your corrections have, sky should be r:23, g:23, b:23 in dark areas of the sky.

Clear skies.


- Andy -


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Thanks for the feedback, I have run SCNR on the green again (I probably did this a bit early in the processing) and adjusted the balance and agree it looks better. I have also cropped it a bit further to remove those stacking artefacts without loosing any interesting detail. I will have a go later with your synthetic flat technique Andy, I had tried something similar but without the Gaussian Blur or adjusting the Offset on the opacity.

Wasn't aware of Arp's loop! so have learnt something else from the image; you do wonder what is a very faint feature and what is just a patch of noise when processing.

The stars could use some more attention, I can see I've introduced some ringing at some point, but think I will try and get some more colour data before going through the whole process again.


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Hi Sam,

:) if an image is well calibrated, just to see what you have (noise, actual features), this can be checked on by the "Equalize command under Image > Adjustments. But, as it isn't really part of (at least my) processing workflow, after checking, one should go back one step (in PS). A quick way to deal with stars would be http://www.astropix.com/html/j_digit/starcolr.html

On your image, it looks good as it is, I don't think a synthetic flat would be needed anymore. Awesome the details you could pull out of a Bortle 8 zone.

- Andy -

Edited by AstroAndy
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Original post edited to include latest revision -

Reprocessed the luminance as I rushed it the first time after spending ages on the RGB image first. Started with some Deconvolution which I completely forgot the first time and then payed much more attention to the noise levels in the background by improving the masks for each process. I then desaturated the background on the RGB image a bit to address the colour patchiness, so this time I didn't need to do a synthetic flat in Photoshop.

Night and day difference! much happier with that. 

Next step will be to see if I can drizzle the luminance data as I have about 70 subs and I'm quite under sampled.

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