Hello everyone, I'm looking for a bit of advice on whether or not the level of noise I'm seeing in my images is too much or not. I've recently been going after IC-63 (Ghost of Cassiopeia) and I've tried to push on the Hydrogen-alpha in the exposures. For reference: - Telescope: William Optics Zenithstar 73
- Camera: Player One Poseidon-M Pro
- Filters: Optolong Hydrogen-alpha 3nm
- Gain: 125
- Sensor Temp: -10c
- Exposures: 78 x 600", totalling at 13 hours
- Dithered every two subs
- Guiding averaged between 0.4"-0.8"
- Final stack set to 1x drizzle (Drop Shrink set to 0.8)
- Calibrated with 30 x darks, 30 x flats and 30 x dark-flats
I see posts quite often here where users share data and I often see comments like "the data is really clean" or "barely any noise" however when I take a close-up look at my images, I don't think I can say the same. Here's the final Ha stacked sub with BlurXTerminator ran over it and the STF applied via HistogramTransformation:  Zooming into a random area with a bit of nebulosity to the left shows the noise:  Perhaps I'm being too critical, I'm not too sure, so I thought I'd ask here to see what others think: is this acceptable? Can you see anything I'm doing wrong from my description above? Is it just a question of needing further integration time? Any advice or recommendations would be welcome.
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What do you expect from 3nm passband and 73mm of aperture @ f/6? The object is intrinsically faint and you aren't even capturing the whole emission/reflection spectrum.
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andrea tasselli:
What do you expect from 3nm passband and 73mm of aperture @ f/6? The object is intrinsically faint and you aren't even capturing the whole emission/reflection spectrum. I suppose I don't really know for sure what to expect, hence my post. Sounds like I'm expecting too much of my equipment by the sounds of things!
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Doesn't look too bad to me, the STF is a bit severe so that isnt helping, try to stretch it normally (in your normal manner) and see what it looks like, get it to a point you're happy with it. I'm assuming you have NoiseXterminator? What does it look like after running that? I wouldnt bother with further integration time, youre already at 13 hours and you would need to go a lot lot longer to get appreciable benefits in the noise.
Also dont forget this filter lets barely any signal through so it's always going to look on the noisy side.
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That's pretty close to what I usually achieve with either of my cameras. Both of which are IMX571 sensors. Though with the seeing in my locale I never shoot longer that 360 second subs. Even that is pushing it most nights. You might try trimming the gain to 100-101. The other thing that may be having an effect on my subs is the offset. I am waiting for a clear night to mess around with that. I presently set to 25, but apparently some allege quality results with offset in the 100-200 range. I've even seen a claim of 700+.
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Looks okay to me, especially with this setup.
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It doesn't look like anything the standard noise reduction tools won't clean up.
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It all depends on what your plans are for the final image. Do you plane to print a 2ft X 3ft poster? if so, then maybe too much noise. Are you going for an IPOD? If so, then maybe too much noise. If on the other hand, you are only going to post on Astrobin, then it's probably fine.
Lynn K.
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Thank you all for your replies. I think in hindsight, I was just expecting a bit too much from my set-up. I think I might try a different gain setting in the future just to see if that changes anything. Whilst I use NoiseXTerminator, I've found that ever since the last update, the image ends up with a weird posterised effect and I end up needing to revert back to the previous AI version and even that sometimes has the same result. Might be a problem with my hardware though as sometimes when I completely close PixInisight then reopen and run NoiseXTerminator again, the image turns out ok, perhaps a caching issue of some kind. Anyway, for those interested, I reached a final image that I'm fairly happy with in the end: https://www.astrobin.com/3qyrs3Thanks again!
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Dan R:
Whilst I use NoiseXTerminator, I've found that ever since the last update, the image ends up with a weird posterised effect and I end up needing to revert back to the previous AI version and even that sometimes has the same result. Do you NoiseX before or after stretching? Before the most-recent update, I had to do it after a stretch as I would get weird artifacts otherwise. The latest update has fixed this for me though. Maybe try switching to whichever you are not doing and see if it helps.
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It looks more noisy than I'd expect for 13h of integration… but then I've never shot this target to know how dim we're talking about - however, I can guarantee you this, any of the noise reduction techniques will have this looking STUNNING in no time at all…
I wouldn't be too concerned.
Oh, another thing you've not mentioned… What are your sky conditions. Despite the 3nm Ha filter, I can assure you that if you're in B8 or B9, you won't avoid noise from sky background/skyglow in your images.. Ha and SII won't be as affected as a OIII filter will, but you will still CLEARLY notice the difference… My setup in dark skies with a full moon up produces cleaner data than when I'm in Bortle 6 in my backyard on new moon… Food for thought.
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