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image problem


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Please can anyone give me an idea of what I have done wrong here?:( This is my first serious attempt of stacking multiple images. I have had attempts in the past stacking three or four 3 or 4 minute exposures but the DSO didn’t show too well. This one is Pacman with ten stacked 5 minute exposures and the same number and exposure time for the dark exposures all stacked with Deep Sky Stacker. I did not include any flat exposures. Phd guided using a QHY5 camera with a f400mm 80mm refractor piggy backed; imaged with a f1000mm Skywatcher 200mm Newtonian and a Canon EOS 300 DSLR, set at ISO 400. I used Photoshop to process.

What I can’t figure out is why there is a large illuminated area on the left of the image and again the DSO isn’t too prominent. The imaging was done in the early hours a few weeks ago and Cassiopea was high in the sky, good conditions and no artificial lighting or other significant light pollution. I did use a CLS filter. I don’t profess to be any sort expert on this, with DSS, Photoshop etc so any tips or pointers would be appreciated. My DSLR camera has not been converted.

Thanks,

Richard

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i'm no expert but according to my experience at astrophotography there is heavy field rotation at your stacked images which is visible at the left of the photo. are you using an eq mount and if so is it properly polar aligned? also the dss may have chosen wrong align points. also at the right of the photo there is noise that might come from your camera or light pollution. the green hue at the left might be from your cls filter. try to stack the photos without the dark frames and try another stacking program. for me nebulosity 2 works just fine at stacking my photos

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You haven't really done anything wrong. To me it just looks like it needs flat-field calibration. The green hue can be dealt with in post processing with your chosen software. I would start with looking at the histogram and you probably find that green&cyan is dominating. Use saturation or curves to dial these down.

hope this helps.

Dave

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Thanks kookoo snd Dave. The guiding was good and it is an eq6 mount, so I reckon the polar alignment was reasonably good. I think I did try without the dark images but from memory it worsened the effects...but I'll look at that again. I'll look harder at the post processing and the nebulosity 2 and see what I get.

Regards,

Richard

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I hope you don't mind but I've had a Sunday afternoon play with your image in Photoshop CS3 just to see what I could find amid all the colour and noise........... well,actually,I worked on just half the image. Anyway,there seemed to be more detail than I thought in there so I tried the full frame......... The latter has been rotated and I think it will have to renamed 'The Ammonite Nebula'......:)

Sorry about that........ still all good fun,eh! :eek:

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Starblazer- I aligned it with the polar scope i.e. aligning Polaris in the little circle and angled the mount with the plough / Cassiopeia but I didn't drift align so I suppose it should be good enough but maybe not perfect.

Cloudwacher.... that's great, I certainly don't mind do you do lessons? I'll have to have a play around in Photoshop and come back with questions.

Thanks to you all for the help and comments,

Regards,

Richard

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it is possible that you polar aligned at the wrong star. in order to check if you use the right star look through your scope at the highest possible magnification. you will see that the Polaris is a double star. also check if the polarscope is properly aligned (check here Astro Babys HEQ5 Polar Alignment). the field rotation could also be a result of the camera rotating at the focuser. make sure the camera is tightened or screwed well at the focuser and that the focuser is locked by the locking screw after focusing

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