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Pages: 1 Star surfer8 professor emeritus Reged: 05/15/06 Odd gradient       #5628570 - 01/17/13 06:01 PM Attachment (22 downloads) Edit   Reply   Quote Quick Reply   Hi, Got my first CCD camera two months ago and of course there hasn't been a clear night since. Finally had a go at first light yesterday with the QSI683wsg and got some RGB frames of IC443. Processed the data today and it looks like there's an odd gradient in the image that I've never seen with DSLR imaging. Have any of you ever had this issue? I would appreciate any help figuring this out. Thanks. Here's a calibrated image taken with the QSI and TOA130 with flattener. Notice the magenta colored gradient in the center. Post Extras:       Star surfer8 professor emeritus Reged: 05/15/06 Re: Odd gradient [Re: Star surfer8]       #5628575 - 01/17/13 06:03 PM Attachment (13 downloads) Edit   Reply   Quote Quick Reply   Here's the uncalibrated version. Post Extras:       Star surfer8 professor emeritus Reged: 05/15/06 Re: Odd gradient [Re: Star surfer8]       #5628583 - 01/17/13 06:06 PM Attachment (7 downloads) Edit   Reply   Quote Quick Reply   Here's the raw red channel. Post Extras:       Star surfer8 professor emeritus Reged: 05/15/06 Re: Odd gradient [Re: Star surfer8]       #5628588 - 01/17/13 06:08 PM Attachment (6 downloads) Edit   Reply   Quote Quick Reply   Raw green channel. Post Extras:       Star surfer8 professor emeritus Reged: 05/15/06 Re: Odd gradient [Re: Star surfer8]       #5628591 - 01/17/13 06:10 PM Attachment (6 downloads) Edit   Reply   Quote Quick Reply   Raw blue channel. Post Extras:       Star surfer8 professor emeritus Reged: 05/15/06 Re: Odd gradient [Re: Star surfer8]       #5628609 - 01/17/13 06:19 PM Edit   Reply   Quote Quick Reply   You can see the gradient in the separate RGB channels and the uncalibrated version. I was able to process some of it out in the calibrated version but it's still there. I've checked the equipment and it doesn't seem to be anything there that would cause this. I'm new to CCD imaging so I'm not sure what to make of this. Like I said, I've never had this issue with DSLR imaging using the same scope. Any ideas would be appreciated. Thanks. Post Extras:       rigel123 Postmaster Reged: 06/29/09 Loc: SW Ohio Re: Odd gradient [Re: Star surfer8]       #5628870 - 01/17/13 08:55 PM Edit   Reply   Quote Quick Reply   It almost looks like some fogging in the middle of each image, maybe on the window of the CCD? Not sure, maybe someone more experienced can weigh in. Post Extras:       shams42 Pooh-Bah Reged: 01/05/09 Loc: Kingsport, TN Re: Odd gradient [Re: rigel123]       #5628943 - 01/17/13 09:45 PM Edit   Reply   Quote Quick Reply   In what order did you shoot the colors? Post Extras:       Star surfer8 professor emeritus Reged: 05/15/06 Re: Odd gradient [Re: shams42]       #5630951 - 01/19/13 01:25 AM Edit   Reply   Quote Quick Reply   Thanks Warren, I duplicated the imaging setup from that night then checked the camera for fogging but the CCD window glass looks clear. Shams, The colors were shot in the order of RGB. How would that affect the cause of the gradient? Post Extras:       Rick J Post Laureate Reged: 03/01/08 Loc: Mantrap Lake, MN Re: Odd gradient [Re: Star surfer8]       #5630978 - 01/19/13 02:02 AM Edit   Reply   Quote Quick Reply   The raw files which I assume means no flats or darks show a hot spot. Looks to me like your flats aren't doing the job removing them and need to be replaced with better ones for each color filter. The red show little hint of a hot spot but blue shows a strong one. Magenta is due to too much red and blue compared to the green. So if the red flat was used on the blue image and the blue flat used to flat the red image that would create the problem as well. Rick Post Extras:       siovene sage Reged: 01/18/11 Loc: Espoo, Finland Re: Odd gradient [Re: Rick J]       #5631510 - 01/19/13 12:49 PM Edit   Reply   Quote Quick Reply   I agree with Rick. Your flats are not working. I actually had the very same problem, and solved it by correctly calibrating the flat frames too, with their dark and offset frames. I didn't want to believe that that was the issue, but it really was. Post Extras:       Pages: 1

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