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Old 21-06-2012, 04:24 PM
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What is this

Hi again

I have been imaging and am having some issues I think.
In the middle of this image at the top there is a dark line that runs down for about a third of the image ... Does anyone have any idea what this may be ... and if so what causes it ???


********** EDIT **********

OK with the help of those who repied I have managed to eliminate the line completely by calibrating my calibration images.
BUT ... if you look to the leftabove the center of the 2nd image (or the first) there is a small black line ... That one doesnt appear anywhere in the calibration images .. ONLY in the camera images and I cant eliminate that one ... see second image below .. Im at a loss again


Thanks again
Attached Thumbnails
Click for full-size image (Capture.JPG)
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Click for full-size image (bias.jpg)
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Click for full-size image (dark.jpg)
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Click for full-size image (flat.JPG)
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Click for full-size image (2nd image.JPG)
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Last edited by Jeffkop; 22-06-2012 at 08:25 AM.
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  #2  
Old 21-06-2012, 04:51 PM
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Looks like a column defect, should be able to remove it using darks. Does it show up an all your pics taken after this one?


Mark
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Old 21-06-2012, 05:06 PM
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yes, mark,
and: does the line show when you review the images on your cam right after taking them?
if the line shows right there in the camera, too, I'll hazard a cheap-fix-guess:
try a different storage card.
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Old 21-06-2012, 06:54 PM
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Really sorry for not realising I should have included this info at the start. The camera is an STL11000. I have used pixinsight and this image has been calibrated with flat bias and dark frames so if it is a column defect then I am not doing the calibration correct. Apart from this the image so far i am happy with. Its only 40 mins (4 x 10 min subs) of clear information.
Should I include a copy of the calibration frames to look at too
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Old 21-06-2012, 06:57 PM
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Quote:
Originally Posted by marki View Post
Looks like a column defect, should be able to remove it using darks. Does it show up an all your pics taken after this one?


Mark
Mark the line is in all the subs, I will check the colour subs and report back
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Old 21-06-2012, 07:20 PM
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Dither whilst imaging.
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Old 21-06-2012, 07:58 PM
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Quote:
Originally Posted by Bassnut View Post
Dither whilst imaging.
Thanks Fred .. How do I do that ???? Manually move the scope by small amounts every sub ????

OK .. Update on the line.
I can see it in the bias frame and the dark frame .. but not in the flat.

--- Edit .. just did an auto stretch ... its also in the flat

Its in every 10 minute sub also ... I guess its a column defect. So im stuck with it




Also if you look at to the left at the bottom of that line there is a smaller one ... That one doesnt appear anywhere other than that calibrated image I have attached.

Thanks again
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Old 21-06-2012, 08:20 PM
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OK .. have added the gammut of images ... If its also in the dark frame in the smae position .. how do I subtract it out ??? ... Oh is that what Fred means about dithering
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Old 21-06-2012, 08:40 PM
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Jeff if you are using maxim it is simple to check the dither box and it will do it automatically, not sure about other programs. How are you calibrating? Sometimes if you get the camera real cold it can lessen the effect you see some what but it still should come out with good calibration frames and a bit of careful processing.

Mark

Last edited by marki; 21-06-2012 at 08:51 PM.
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Old 22-06-2012, 11:31 AM
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Hi once again

OK I have solved all the problems.
Pixinsight has a process called cosmetic correction that is used to eliminate hot and cold pixels via a couple of different methods. It has totally eliminated that small line, hopefully replaced it with suitable pixels.

Heres a view of the image so far. Its 40 mins - clear filter (4 x 10min subs) with all the line blemishes removed. I am happy with it .. what do you think.
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Old 22-06-2012, 03:50 PM
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Its a hot pixel giving a line as the CCD is read out. It isn't a colomn defect as that is an entire column. You need to use a defect map as well as dark frames etc as when some pixels are defective they will produce variable levels with each exposure so this won't dark frame out fully.
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Old 22-06-2012, 04:13 PM
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I've got one in my camera.

Maxim's Remove Bad Pixels thing works a treat. I run it as a batch process before doing calibrations. Mine doesn't reliably disappear with dark frames, so I guess it might be something along the lines of what Terry says - thanks for educating me on that one too Terry!

DT
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Old 22-06-2012, 09:29 PM
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Quote:
Originally Posted by marki View Post
Jeff if you are using maxim it is simple to check the dither box and it will do it automatically, not sure about other programs. How are you calibrating? Sometimes if you get the camera real cold it can lessen the effect you see some what but it still should come out with good calibration frames and a bit of careful processing.

Mark
I use ccdsoft Mark ... Have dloaded a 3rd party autodither but it doesnt work. Thanx anyway ... Will try maxim

Quote:
Originally Posted by Terry B View Post
Its a hot pixel giving a line as the CCD is read out. It isn't a colomn defect as that is an entire column. You need to use a defect map as well as dark frames etc as when some pixels are defective they will produce variable levels with each exposure so this won't dark frame out fully.
Thx Terry .. Tried to use the defectmap in pixinsight ... Which ever image i try to usein that process I keep getting a "locked error"

Quote:
Originally Posted by DavidTrap View Post
I've got one in my camera.

Maxim's Remove Bad Pixels thing works a treat. I run it as a batch process before doing calibrations. Mine doesn't reliably disappear with dark frames, so I guess it might be something along the lines of what Terry says - thanks for educating me on that one too Terry!

DT
May well swap to maxim Dave ... I think i have actually been succesful ingetting rid of the problem tho ... Thanx
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