Guest Posted October 28, 2012 Share Posted October 28, 2012 Hi,I have recently purchased an Atik 460EX, and have begun to image with it, having been used to using my friend's Atik 314L+. I have noticed on all the images I have so far processed a very strange effect in the background of the images when zoomed in a bit- I can't really describe it, its not exactly grainy, I have never experienced it before. I am obviously doing something wrong in my processing, but am not sure what! The effect is there in narrowband and colour images- I have attached an image as an example, it does have to be zoomed in to show the problem. Any advice would be most appreciated!Zoe Link to comment Share on other sites More sharing options...
Spikey Posted October 28, 2012 Share Posted October 28, 2012 Looks like common or garden sensor noise to me Link to comment Share on other sites More sharing options...
swag72 Posted October 28, 2012 Share Posted October 28, 2012 I too thought it looked like noise.Are you doing anything different with the 460 compared to the 314L+ you've been using? The cooling perhaps?Interested to follow this as I'm placing an order for a 460 in the coming week and I currently use a 314L+. Link to comment Share on other sites More sharing options...
Martin-Devon Posted October 28, 2012 Share Posted October 28, 2012 I agree with Spikey - looks like background, possibly with a Luminence filter under moonlight conditions. I also have an Atik 460EX & an Atik 314L+ and the 460 is certainly not a noisy camera, but it is very sensitive, so be careful with LRGB if moonlight is around. I'm not sure if you've subtracted calibration frames either - darks & flats - have you done these? Link to comment Share on other sites More sharing options...
Gina Posted October 28, 2012 Share Posted October 28, 2012 Nice image but definitely looks noisy to me. Link to comment Share on other sites More sharing options...
Guest Posted October 28, 2012 Share Posted October 28, 2012 Hi,Thank you all for your quick responses. I have had the same effect on images taken without a moon, and have tried adding dark frames, though haven't got around to the flats yet. Noise removal seems to make it worse if anything! It occurs with both colour and narrowband filters. The camera is being cooled to the same temperature that we use with the 314L+, ie -15 c. Cannot think of anything which is different Am thinking it must be noise of some sort... Link to comment Share on other sites More sharing options...
Gina Posted October 28, 2012 Share Posted October 28, 2012 Could it be condensation I wonder Link to comment Share on other sites More sharing options...
badgers Posted October 28, 2012 Share Posted October 28, 2012 That noise looks pretty standard to me, especially given that it is a crop.If I image faint targets or on moonlit nights I see the same thing. The key thing with the 460ex is that the thermal and sensor noise are very low so this read or shot noise will vanish after stacking very quickly.If you have an example before and after stacking that would help diagnose a problem if there is one. Link to comment Share on other sites More sharing options...
Guest Posted October 28, 2012 Share Posted October 28, 2012 Hi,I willl post before and after pix soon, but this effect seems to appear most strongly after stacking, and any other processing seems to amplify it; the posted image is processed. Don't think there is a problem with the camera, probably just my processing! Link to comment Share on other sites More sharing options...
badgers Posted October 28, 2012 Share Posted October 28, 2012 Hmmm that does sound weird -.-Although it took me ages to get to grips with processing mono images there are certainly plenty of places to go wrong.What processing tool are you using ? Link to comment Share on other sites More sharing options...
x6gas Posted October 28, 2012 Share Posted October 28, 2012 What power source are you using to run the camera? I found my 383L picks up noise if I have the power cable too close to other things; I use to have the power for the camera as part of loom that also had power for the filter wheel, guidecam, and 3 USBs. That was causing the sort of noise you are seeing so now I leave the camera power on a separate cable... Link to comment Share on other sites More sharing options...
ollypenrice Posted October 29, 2012 Share Posted October 29, 2012 Zoe sent me a fullsize JPEG and up close the pattern is easy to see. There are artefacts created in blocks of pixels. At first I thought they were all 8X8 because that was the case in the first zoom into pixel scale that I did. However, the size of the blocks seems to vary. I've no doubt, though, that there is a pattern of noise imposed on the image at the scale of small blocks of pixels. I've just looked at a block which clearly has two dark stripes running up it. Other blocks have a dark corner and a light corner, etc. But they are surely blocks. This is quite unlike any noise I've seen before and I can't explain it. I hope to see a small bit of 'straight from camera' FITS to confirm that the same pattern exists prior to processing.I rarely image at all in moonlight and never touch anything but Ha when I do so, I don't know if moonlight can do this. Has anyne else seen noise at the scale of systematic blocks of pixels before?Olly Link to comment Share on other sites More sharing options...
ollypenrice Posted October 29, 2012 Share Posted October 29, 2012 Me again. Back to plan A. I think the pixels blocks are consitently 8X8 after all. Here is a resized crop of a fragment showing several blocks. I know resizing is hardly the way to do it (!!!) it but I couldn't think of another way to make it visible on the forum and it does, I think, show the pattern really well. Why would moonlight strike in 8X8? I think this is an electronic effect. However, I haven't a clue on the intricacies of read mechanislms etc etc. Any ideas?OllyMods, might this be better on a different board? Link to comment Share on other sites More sharing options...
Earl Posted October 29, 2012 Share Posted October 29, 2012 Could that be JPG artifacts due to compression? only a Fits or Tiff will really show. Link to comment Share on other sites More sharing options...
NickK Posted October 29, 2012 Share Posted October 29, 2012 JPEG also compresses by sub-dividing into blocks as Earl has indicated. Link to comment Share on other sites More sharing options...
Guest Posted October 29, 2012 Share Posted October 29, 2012 Hi all,Thank you all for your replies, and thank you, Olly, as I was beginning to think I was imagining things! This occurs with or without moonlight and through any filter, doesn't change between fits, tiff and jpeg and all my images are definitely binned x 1. Haven't seen the effect on anyone else's images from the same camera... Link to comment Share on other sites More sharing options...
Gina Posted October 29, 2012 Share Posted October 29, 2012 Could that be JPG artifacts due to compression? only a Fits or Tiff will really show.I wondered that too. Link to comment Share on other sites More sharing options...
Gina Posted October 29, 2012 Share Posted October 29, 2012 Hi all,Thank you all for your replies, and thank you, Olly, as I was beginning to think I was imagining things! This occurs with or without moonlight and through any filter, doesn't change between fits, tiff and jpeg and all my images are definitely binned x 1. Haven't seen the effect on anyone else's images from the same camera...Oh dear - I wonder if you've got a duff camera Link to comment Share on other sites More sharing options...
VigdisVZ Posted October 29, 2012 Share Posted October 29, 2012 Yeah those squares look like JPEG to me. Only use loss-compression when posting on the web, otherwise stay with loss-less saving.Edit: I realised you've said you tried other formats, but it's the only thing that pops to mind at the moment. Link to comment Share on other sites More sharing options...
Guest Posted October 29, 2012 Share Posted October 29, 2012 Oh dear - I wonder if you've got a duff camera I am wondering that myself now... Link to comment Share on other sites More sharing options...
Spikey Posted October 29, 2012 Share Posted October 29, 2012 Just thinking out aloud here but is your original image a single sub or a stack?Might be a pain but I'd be interested in seeing a stack of subs with no calibration at all, purely from the point of simplifying any diagnosing. Link to comment Share on other sites More sharing options...
AndyUK Posted October 29, 2012 Share Posted October 29, 2012 Mods, might this be better on a different board? I think you're right, Olly - For future reference I think it would be better not in the images thread, although whether it's a processing or hardware issue still appears to be up in the air. I'm too very interested in the result of this thread as although I'm not close to buying a 460, I would like to be... Link to comment Share on other sites More sharing options...
Guest Posted October 29, 2012 Share Posted October 29, 2012 Hi,The image I have posted here is a processed stack, however, I will post an unprocessed image later when I get home. The effect definitely seems to occur without any calibration at all. Link to comment Share on other sites More sharing options...
Spikey Posted October 29, 2012 Share Posted October 29, 2012 Ah OK Zoe, I've seen that sort of noise creeping in from bad BIAS calibration in the past but if it's un-calibrated I can forget that idea Link to comment Share on other sites More sharing options...
ollypenrice Posted October 29, 2012 Share Posted October 29, 2012 I hope Zoe will send me a fairly small bit of 'from-camera' FITs with nothing done at all. I need enough to look at about 100 pixels on a square and then I think it'll be one for Steve Chambers at Atik. Dennis Isaacs tells me that JPEG works 8x8 which is a clue or a coincidence.Zoe, did you capture in Artemis Capture? I just wonder if another capture programme might mess with the data.Olly Link to comment Share on other sites More sharing options...
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