ashenlight Posted June 25, 2009 Share Posted June 25, 2009 A simple question which I am sure will yield very informative answers....How does one reduce noise in images? I ask because I am about to rush into an attempt to do some widefield astro photos. Once I up the ISO I'm sure the photos (do we call these 'subs'?) will suffer from noise... what can I do to remedy this? Link to comment Share on other sites More sharing options...
Aza Posted June 25, 2009 Share Posted June 25, 2009 Ideally you want to take many subs of the same target.Then stack them all up with software.By doing this you increase the SNR, which is the signal to noise ratio.For best results though you need to be shooting in RAW format, rather than jpeg. Link to comment Share on other sites More sharing options...
SteveL Posted June 25, 2009 Share Posted June 25, 2009 Ah, welcome to the dark side Take many images of the same target, and then stack them. As the noise will be random in every shot, stacking will remove much of the noise. Link to comment Share on other sites More sharing options...
Ant Posted June 25, 2009 Share Posted June 25, 2009 You could also take a dark frame and then remove the noise in the post processing...Ant Link to comment Share on other sites More sharing options...
SteveL Posted June 25, 2009 Share Posted June 25, 2009 For the same reason as above, you would need to take several darks, as using only one dark when stacking will add more noise into the final image. Link to comment Share on other sites More sharing options...
blinky Posted June 25, 2009 Share Posted June 25, 2009 As the others have said but you also get some noise reduction plugins for Photoshop. I usually run Neatimage after final processing to remoe any residual noise. THe most important thing is to take loads of subs though. Link to comment Share on other sites More sharing options...
themos Posted June 25, 2009 Share Posted June 25, 2009 Ah, the holy grail...See if this makes any senseSignal to Noise: Understanding it, Measuring it, and Improving it (Part 1) - Articlethere's also a part deux Link to comment Share on other sites More sharing options...
brianb Posted June 25, 2009 Share Posted June 25, 2009 You could also take a dark frame and then remove the noise in the post processing...That helps with repeatable noise sources (amp glow) but not with quantum noise - the only cure for quantum noise is is increase the number of photons detected. Don't use a very high ISO setting. Shoot in raw mode, set the ISO to about 400, take lots & lots of subs (making the exposure for each sub as long as the tracking and/or light pollution will allow) & stack them in Deep Sky Stacker. Link to comment Share on other sites More sharing options...
ashenlight Posted June 25, 2009 Author Share Posted June 25, 2009 Wow, what fantastic and fast responses, thank you.I'm going to have a proper read through and try and let it sink in. Be prepared for a deluge of questions Link to comment Share on other sites More sharing options...
Aza Posted June 25, 2009 Share Posted June 25, 2009 I pretty much learnt everything I know from this forum!So you are are definitely at the right place.Just beware that it is a slippery slope.Once you get a taste you keep wanting to move up a level! Link to comment Share on other sites More sharing options...
Psychobilly Posted June 25, 2009 Share Posted June 25, 2009 See its an irresistable force.... Link to comment Share on other sites More sharing options...
James Posted June 25, 2009 Share Posted June 25, 2009 Careful Amanda, imaging is a dangerous addiction that snared me last autumn. To give an idea of the danger I'd been a fairly rabid visual only observer for over 20 years and have sworn that I'd never image - there's probably posts of mine saying that. How wrong I was Link to comment Share on other sites More sharing options...
SteveL Posted June 25, 2009 Share Posted June 25, 2009 Kelling was great last Sept, it was the transformation of James. "Oh I wont get pulled in, i am a visual observer only, dont want to dabble in the dark side, wont be interested, blah blah blah"... then that first sub of NGC7331 popped out and onto the screen. You were standing behind Steve (FLO) and Michael (SX), hoping that no one would notice that you were lighting up the field with that wide grin you had.... oh yes, we noticed... Link to comment Share on other sites More sharing options...
ashenlight Posted June 25, 2009 Author Share Posted June 25, 2009 Hahahaha Steve that is a brilliant story, poor James lol! I am smiling like an idiot at the mental image of that.You should be encouraging this James I may buy my first CCD from FLO in a year or so, you never know Out of interest, why did you swear you'd never image? Was it because you knew what a slippery slope it was? Link to comment Share on other sites More sharing options...
James Posted June 25, 2009 Share Posted June 25, 2009 It's a long story really and I'll spare everyone the details (for now ) but ironically the reasons I didn't want to image turned out to be pretty much the reasons that I ended up wanting to image, sort of.It is a slippery slope... Link to comment Share on other sites More sharing options...
Psychobilly Posted June 25, 2009 Share Posted June 25, 2009 Imaging will show you things that the MK1 eyeball never will... and whilst there are Zillions of brilliant images all over the WWW there's nothing quite like capturing and processing the image yourself... probably similar to teh experience of "glimpsing" a faint fuzzy blob with the Mk1 EB... but as the sig says....Imagers do it in Glorious TECHNICOLOR or Narrowband... Link to comment Share on other sites More sharing options...
ashenlight Posted June 25, 2009 Author Share Posted June 25, 2009 James, I will have to get that story out of you at SGL5 perhaps we may need to beer induce you first? Yea Peter, can't imagine the pride and joy brought about by seeing your very own image appear on the screen, after all the time capturing, processing... must be such a thrill I have made it my mission to capture M42 come the winter. Even if it's in an Orion widefield.... Link to comment Share on other sites More sharing options...
Ant Posted June 25, 2009 Share Posted June 25, 2009 Kelling was great last Sept, it was the transformation of James. "Oh I wont get pulled in, i am a visual observer only, dont want to dabble in the dark side, wont be interested, blah blah blah"... then that first sub of NGC7331 popped out and onto the screen. You were standing behind Steve (FLO) and Michael (SX), hoping that no one would notice that you were lighting up the field with that wide grin you had.... oh yes, we noticed...I also remember that clearly, I'd just finished talking to grant and happened to walk past James et al. Beaming from ear to ear as I recall!!!!It is a slippery slope, but it's a fun slope!Ant Link to comment Share on other sites More sharing options...
ashenlight Posted June 25, 2009 Author Share Posted June 25, 2009 I'm very excited about this now Expect to be irritated by my little Welsh self at SGL5.... Link to comment Share on other sites More sharing options...
samtheeagle Posted June 26, 2009 Share Posted June 26, 2009 I have made it my mission to capture M42 come the winter. Even if it's in an Orion widefield....Ditto I'm still very new to imaging, but I can see why visual observers consider it to be the dark side. I've spent hours outside with my scope, and not really looked at anything once I had lined up for the shot. I must admit that I do sit there waiting for the subs to stack up thinking "what the hell am I doing here?". But once you get all the data on to the computer and you see the image coming together it's a real buzz!That's said I'm hoping to remain a 50/50 type, I still love just looking at stuff. There's more of a connection when you are actually seeing something first hand, even if it is small, fuzzy, devoid of colour information Link to comment Share on other sites More sharing options...
themos Posted June 26, 2009 Share Posted June 26, 2009 I must admit that I do sit there waiting for the subs to stack up thinking "what the hell am I doing here?".That's what the Dobsonian is for. Link to comment Share on other sites More sharing options...
jgs001 Posted June 26, 2009 Share Posted June 26, 2009 Or a pair of bins Themos... I'm going to having another go at M42 as well Amanda. What hasn't been discussed is what camera do you have ? Link to comment Share on other sites More sharing options...
barkis Posted June 26, 2009 Share Posted June 26, 2009 What a pleasure it is to read a thread with nothing but excitement, anticipation, and expectation in it. And all revealed in just a few posts. This is the very good part of SGL.Ron. Link to comment Share on other sites More sharing options...
samtheeagle Posted June 26, 2009 Share Posted June 26, 2009 That's what the Dobsonian is for.Lol, yeah a second scope would help a lot... I'll start working on getting the required wifal approval Link to comment Share on other sites More sharing options...
Doc Posted June 26, 2009 Share Posted June 26, 2009 Hope you have deep pockets Amanda Link to comment Share on other sites More sharing options...
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