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Why is this so....messy?

Russell Croman Astrophotography BlurXTerminator Russell Croman Astrophotography StarXTerminator Pleiades Astrophoto PixInsight Request for feedback
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Piers Palmer avatar
Piers Palmer avatar
I shot the Crescent Nebula last night and managed to get 107x180" frames, using my ASI2600MC Pro on an Askar FMA230 at gain 100 and cooled to -10º. 

https://astrob.in/9nnnu7/0/

I've stacked in Pixinsight and processed using a combination of Starxterminator, Blurxterminator, Generalised Hyperbolic Stretch and some other little curve tweaks. 

Compared to similar shots taken by fellow members with the same equipment (but far less integration time), my image is very....noisy?

Can anyone advise? Is there something wrong with my individual frames perhaps?

Here's anindividual frame and the masterlight is here if anyone was really bored. 

Any advice, gratefully received.
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Thomas avatar
Thomas avatar
You massively overstretched your data. Depending on your sky background, you'll have to invest more imaging time to get better SNR or/and use an LP Filter.
In addition to that, there is quite some walking noise, this can be mitigated by dithering.

all the best
Thomas
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Piers Palmer avatar
Piers Palmer avatar
Ah, ok. I do dither every third frame (maybe I’ll check that) and I have an sqm reading of 21.2. I know the moon is out but I was hoping my NBZ filter would have made up for it. 

The reference shot I’ve compared mine to was using the same camera, settings and far less integration time but is much nicer than mine. 

Maybe I’ll try again.
Quinn Groessl avatar
Quinn Groessl avatar
I was able to get quite a bit more detail out of the main nebula bit when I worked your data, but as Thomas said, the walking noise is tough to deal with. I did to try and hide it, by darkening up the image quite a bit more than I would like.

Piers Palmer avatar
Piers Palmer avatar
Thank you! I shall definitely check the dithering is on. If it is then maybe I need to dither by more and more often?
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Thomas avatar
Thomas avatar
Piers Palmer:
I know the moon is out but I was hoping my NBZ filter would have made up for it.

The reference shot I’ve compared mine to was using the same camera, settings and far less integration time but is much nicer than mine.

Maybe I’ll try again.


You are working with a quiet small focal length, make sure your dithering distance is big enough /increase it just in case.
SemiPro avatar
SemiPro avatar
The walking noise is pretty bad. If you are not dithering you need to do so, and if you are then you need to either increase how many pixels you are dithering or decrease the amount of sub-frames shot before dithering.

Also, I am not sure what your light pollution level is, but you may want to think about increasing your exposure time on each sub-frame because unless you are in a crazy high bortle level, 180 seconds is pretty short.

Be careful judging other people's images by total integration time because their sky conditions could be vastly different than yours.

————
Okay wow a lot of people posted in the few minutes that I was writing this comment! They covered everything I did so this is all redundant now!
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Piers Palmer avatar
Piers Palmer avatar
Thanks. Bortle 3/4 according to my SQM meter but being in the north of England there was probably lots of thin cloud; it’s rarely clear. My tracking was fine so maybe I’ll try 5 min subs next time. Better for my hard drive too!
andrea tasselli avatar
andrea tasselli avatar
180s is plenty but you need more integration time overall with such a small aperture.
Quinn Groessl avatar
Quinn Groessl avatar
Quinn Groessl:
I was able to get quite a bit more detail out of the main nebula bit when I worked your data, but as Thomas said, the walking noise is tough to deal with. I to try and hide it I darkened it quite a bit more than I would like.


And as usual I forgot to mention what I did. ABE - subtraction. SPCC, Crop, BlurX - left the sliders alone but checked nonsteller than steller, StarX, arcsinstretch to the stars, HT for the nebula (I suck at GHS still), Curves in RGB/K, L, and S, Color Saturation - Bumped up everything but the green, SCNR - .85 Green, .4 blue (it had a weird hue to it), stars+starless pixelmath, NoiseX - bumped the detail up a bit, and then played with the curves just a touch more.
Piers Palmer avatar
Piers Palmer avatar
andrea tasselli:
180s is plenty but you need more integration time overall with such a small aperture.

Or accept the constraints conditions/equipment impose? That’s another choice I guess.

I’ll have another go this evening in front of the footy and see a what I come up with.
Piers Palmer avatar
Piers Palmer avatar
And as usual I forgot to mention what I did. ABE - subtraction. SPCC, Crop, BlurX - left the sliders alone but checked nonsteller than steller, StarX, arcsinstretch to the stars, HT for the nebula (I suck at GHS still), Curves in RGB/K, L, and S, Color Saturation - Bumped up everything but the green, SCNR - .85 Green, .4 blue (it had a weird hue to it), stars+starless pixelmath, NoiseX - bumped the detail up a bit, and then played with the curves just a touch more.

Thank you so much!