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Hello I`m having issues with stacking 2 nights of data. Both nights i plate solved so every frame lines up. Quality does vary but for some reason when i stack both nights the end image comes out and the red green and blue bars instead of being solid are segmented and the histogram is only one bar (not the usual 3). I know i should be using WBPP but my laptp just doesn`t have the oomf (power, RAM). I`m using calibration frames. Im just pulling my hair out with why its not working. Does anyone have any ideas? The whole point of plate solving is so you can image one target mulitple nights….. Thanks for reading CS Alan |
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Not sure I follow you on this… What exactly isn't working? You calibrate then what? And, are you using PI?
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When i stack more than 2 nights of data i`m unable to process the end image as there is information missing in the histogram. Usually the end image has 3 peaks (RGB). When i stack this data there is only 1 peak and the streched image has no data. I`m using calibration frames but this doesn`t seem to make any difference. I`ve tried stacking with and without calibration frames but it doesn`t make any difference.
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Alan Hancox: If you were to process each night separately would that result in a viable image? You mentioned WBPP which means you have PI but now you use DSS, correct? |
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I do have PI but my laptop isn't powerful enough to use WBPP. It takes an eternity to process anything tbh. I need another one but funds are tight atm. Yes if I stack each night separately it works but not if I combine the subs and only use the best frames. Hth |
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Then don't use WBPP which hogs up resources like there is no tomorrow. Do the process one step at the time and albeit slowly it will undoubtedly converge to the final results. I'm used to a very slow, 8GB laptop and it was a pain but eventually it did make it. At any rate you could still use the two night's frames and combine them together in PI using StarAlignement and then add them up in PixelMath.
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Do the exposure lengths, Gain or ISO settings, any filters used, and image size match up from each night?
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Hi Alan, Like many other folks, I've had my share of stacking issues with DSS but, like @andrea tasselli I'm not quite sure to understand what you actually get as output. In particular I'm having trouble picturing what you mean by "end image comes out and the red green and blue bars instead of being solid are segmented". Do you mind uploading a screen shot of your final image (as displayed in DSS) along with the histogram you get. That could really help understand what you get and narrowing down the problem you're having. |
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Are you using flat and dark frames? If so examine each of those to make sure there isn't anything odd about any of them. I am not sure I was having the same problem you are having but I remember having some odd problem that I could not figure out until examined those and discovered there was a problem with one or more of the frames I was using. |
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Scott Alber: I would second Scott's suggestion. Some of the most annoying stacking issues I've had were caused by bad flats. But now, if I understand correctly, you did try to stack without calibration frames and got the same problem, correct? |
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Check your settings in Raw/FITS settings in DSS. I ran into similar issues and figured out the DSS wasn't reading the files correctly. Go the the FITS file tab and click the first box (monchrome 16 bits). Then ensure that you have selected the correct Bayer pattern and bilinear interpolation. That worked for me. |
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Alan- have you tried to put each night into a new group tab rather than all of the subs in the main group? I have had different outcomes doing that. DSS will register even if each sub isn't perfectly matched to the others, so plate solving won't really impact your stack and registration. And only because I"ve done it by accident, make sure the cal frames are inputted as lights… |
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I like DSS although I realize that WBPP is probably better. I'm assuming you are stacking OSC data. I would try to put all of the lights into one group and let DSS register everything as opposed to putting the separate night's work into separate tabs. As you mentioned, the images should be very similarly framed since we're using plate solving. You did not say whether or not the restulting stack is a color image or monochrome so, and this might sound overly simplistic but make sure under "options-settings-raw/fits/DPP settings-fits files" that you address the checkbox at the top of that dialogue box appropriately, i.e. specifying if you are processing monochrome images or those created by a color camera. In my paricular situation, I image almost exclusively in monochrome but every now and then, I do a OSC image and I always forget to change this setting. I hope this helps! |
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I think the screenshot showing the Light will be more useful than the flats. and I think that what Rick asked. A couple of comments from your first screenshot. First, Something I see at the very top) is the "(1 frame)". There definitively a problem here, this is reflecting the total number of light frames which have successfully been stacked. So it does look like DSS has "stacked" only one frame. However, the puzzling thing is that the time indicated is 5h57, which doesn't seem to correspond a single frame. I've tried out of curiosity to "stack" one frame and DSS doesn't seem to mind. Second, and somehow related to the previous comment. The histogram does NO contain any data. In the little test I've just mentioned, I've "stacked" a 3s exposure (meaning that it's pretty dark with very little info). STILL, I get a broad histogram in the shadows. Based on these two points, It looks like DSS is "stacking" only a single frame of 5h57 which contains no data. |
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You might want to try adjusting thre Star Detection Threshold, which can be accessed via Settings - Register Settings - Star Detection Threshold. I use 8% but you'll need to experiment - too low and it won't find enough stars to regisiter and align. Graham |
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This will happen if your light frames are moved into a different folder after you've loaded them into DSS or the drive has briefly lost connection.
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What do you mean the drive has briefly lost connection? I don`t understand…
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Alan Hancox: Alan, sorry, but it is mostly the lights I am looking for. I want to see if the images are registered properly and that the offsets are computed correctly. If you can, right after stacking, take a look at the file list. You access it after stacking by clicking in the upper left box, anywhere should work. You don't need to click on any of the links. If you click on the link, a window will pop up. Close it, and the file list will be there. You need to do this right after the stack, as computed offset info (dx,dy) is not saved. Rick ![]() |
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Alan Hancox: You mean 500 for the quality threshold? I tend not to use that, it is really hard to judge what value to use and you may throw out a lot of good frames or include many bad frames. What I do is look at the score list as you have above. Look at the worse score images, zoom in and see if they look bad or not. Also look at the FWHM, if there are a few that high compared to the others uncheck that file. similarly I look at the worst background, if they are much worse than the rest of the files I uncheck them (I actually just delete them if I can see they are bad). I don't trust just setting an arbitrary quality number. Unfortunately, the columns on the right are cut off. Can you narrow these visible columns so all the columns are visible, stars, background, FWHM, etc. I am curious how many stars you detected, 1000 is a very high score suggesting you are getting a lot of stars. Ideally about 50 to 100 stars is the target. More than that will cause problems. So if it takes noise as stars, thenall the offsets shown here can be off. I assume the 342(3), 342(4) are imaged sequential? If so, for the most part they look okay, in that there are not big shifts from consecutive frames. If you are guiding then they all should be nearly identical from the same night. There is a big jump between 3 and 5, and another big jump from 8 to 10. Did you dither? If these are all sequential and guided without dithering than it may be your star threshold is too low, letting noise be used to calculate the offsets. So if some frames are offset from where they should be, then anything in your image tends to get wiped out, as they are out of register. Also, what kind of averaging did you do? If you are not doing a simple average try that first to make sure that is not part of the problem. Rejection methods only work well when the images are similar, particularly bad if background is changing a lot, can cause all sorts of problems. Do you know how to adjust the star detection? Under register click the advanced tab, and move the slider to adjust. Click compute the number of detected stars. This is an estimate based on one of the image files, but it gives you an idea. The selection threshold here is a % of full well. So for example, if my background % is say 0.5%, then the threshold is set above the background, generally I run 2 to 4% depending on how many stars in the area. If you background is 5%, then the detection must be well above that other wise you will get noise counted as stars. Do you know what threshold was set for and again, if I can see the stars column, I would like to see what that is showing. ![]() I have another suggestion, if you can take say 5 light frames from each night, and one dark. one flat and one flat dark and reproduce the problem, then perhaps you could load that to dropbox or google drive, so I can go in and try to see what is wrong. You could load everything, but that is a lot of time and effort. Since the problem occurs when you have both nights, there may be a minimum set of frames that still causes you trouble, that I could troubleshoot with my DSS. Rick |