Dark line ridge in CCD image

[cardconvict]

Hello I'm trying to process my images with a CCD starlight xpress 694 mono camera. On my images I know there is a dark band running down the picture from top to bottom.  The issue is for me that when stacking I cannot seem to remove this band. I'm dithering and using darks, flats and bias frames and still the band remains. am I doing something wrong as I was under the impression the vertical lines were removed by calibration files in the bias frame.

 

I have attached a master file if someone would not mind having a look for me.

HA MASTER.xisf

[ollypenrice]

I don't know why stacking hasn't removed this but it's a totally trivial defect which can be cosmetically repaired easily. I deal with worse than that, believe me!

For diagnostic purposes it's worth noting that there are two pairs of parallel lines, a light and a dark both repeated. If you look at a single sub, what do you see? Is it two parallel pairs like the master or is it just one pair? Or something else?

When you stacked, did you use a sigma stacking routine? That's the best for this purpose but not all Sigma routines are equal. AstroArt's, which I use, has improved over updates of the program.

AstroArt also lets you identify bad columns prior to the stacking stage and the columns will be given the average values of the pixels on either side. And it also has a 'Remove Line' feature which you can use when all else fails.

Olly

[cardconvict]

Hello Olly

thank you for helping me I have also attached a single sub. Seems there is only one column on the single sub.

 

My master bias shows the defect much more clearly

For stacking I'm using Pixinsight but I'm learning how to use it. I have been away from this awesome hobby for over 4 years due to conditions where I use to live.

I don't think its the white lines but the dark linein the middle of the 2

 

1.81_NGC 2244_HA_LIGHT_2022-02-26_-20.30_300.00s_0004.fits

Edited February 28, 2022 by cardconvict

[ollypenrice]

Column defects are quite common and if you stacked in AstroArt you could lose them by using the column defect feature. I dare say other stacking software has an equivalent but, if they don't, they should! The bias won't show you a column not responding properly to light, remember. I thought you had a dark column, or rather two, in the master light.

Olly

Edited February 28, 2022 by ollypenrice

[cardconvict]

ok so in the master light there is 2 dark lines but in a single sub there is only one dark column which is very faint. I wonder from dithering every 2 frames has added more lines into the stacked image and made them more pronounce. I will have to look into pixinsight as there is a feature to remove columns/rows just need to learn the software more. 

 

[ollypenrice]

32 minutes ago, cardconvict said:

ok so in the master light there is 2 dark lines but in a single sub there is only one dark column which is very faint. I wonder from dithering every 2 frames has added more lines into the stacked image and made them more pronounce. I will have to look into pixinsight as there is a feature to remove columns/rows just need to learn the software more. 

 

I think this may be what's happening, yes.

Olly

[gorann]

Just identify the column number and use Cosmetic correction in PI to remove it (average from the neighbouring columns just like in Olly's AstroArt). There are good free videos on the net that will show you how to do it in PI (I expect you find it by just googleing "bad columns Pixinsight" or "Cosmetic correction Pixinsight").

[cardconvict]

Thank you I will have alook at that