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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 an individual frame and the masterlight is here if anyone was really bored. Any advice, gratefully received. |
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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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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. |
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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. |
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| 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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Piers Palmer: |
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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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| 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! |
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| 180s is plenty but you need more integration time overall with such a small aperture. |
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Quinn Groessl: 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. |
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andrea tasselli: 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. |
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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! |
