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發表於 2008-1-4 12:10:31
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原帖由 ultraman 於 2008-1-4 04:29 發表
I used EM200 and SXV-M25C One-Shot Camera to take this 720s image with Bin 2x2 with dark and flat subtracted. Only one 720s image was used, no stacked.
How can I get rid of the vignetting on the r ...
Ultraman, let me try to comment on your several queries:
1) flat-fielding should get rid of vignetting if done properly. How did you do it? You mentioned you subtract the flat? If you really mean that, its not right since flat should be divided. There are no easy ways to do flat-fielding in Photoshop. Did you use other software? I use ImagePlus. Many others use MaxIm DL or others.
2) If you get a "gradient" from your dark. You should also get it on your light frame. After you subtract the dark, your light frame should look fine. If the "gradient" only appears on your dark frame, may be there is something wrong. You should check your procedure. On the othe hand, its a good idea to take multiple dark frames and than average or median combine them to form a master dark before use. Similarly for flats.
3) Glow around bright star is kind of normal. You can reduce the "glow" by various methods. I found the easiest to use photoshop actions by Noel Carboni (http://actions.home.att.net/Astronomy_Tools.html). I highly recommend his tool set, very useful. I can't see any obvious blooming on your image. If there are, you can remove it manually or use some tools to assist.
4) I usually just use Save As in photoshop to save my files. Note that you need to set the mode to RGB and 8-bit before you can save as jpeg in earlier versions of photoshop.
On the other hand, I also found Russell Croman's GradientXTerminator (http://www.rc-astro.com/resources/GradientXTerminator/index.html) an indispensible tool to remove gradient - which is very serious at my site. Without proper dark, flat and gradient removal, you cannot bring out all the details in your image.
Hope this helps.
[ 本帖最後由 anguslau 於 2008-1-4 12:14 編輯 ] |
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