What you are seeing here is a column defect - they can be eliminated by proper calibration or dithering.
Column Defects are CCD camera pixels that usually still function but respond to light slightly differently than their neighboring pixels. The “defects” look lighter or darker than the rest of the pixels that surround them. The amount of difference from its neighbours that classifies a pixel as defective depends on the model of the CCD detector or chip. These can appear as dark spots/clusters, columns or points.
This type of defect is normal and all CCDs have them to one degree or another, although they usually only show it in certain cases, when light is hitting from a specific angle.
In most cases, stacking software like MaximDL and CCDStack, have the ability to do a data reject, which will remove these from your final image.
One suggestion we would make when taking multiple images (if you haven't already), as it will help with rejecting data to get you high SNR, would be to select the "Dither my images" box in the Session Options of the advanced section. This forces the CCD to take each exposure from a different part of the CCD chip, which results in slight variables between each image, allowing algorithms like Sigma reject to see those variables, and remove them. In 90%+ of cases, when images are dithered, a column defect will be removed during the reject.
Another method is described below. See Images attached. Our thanks to Pal Brias.
Processing method to eliminate bad vertical lines from FITS images with astronomical picture processing software.
These lines are speciality of very high quality SBIG STL 11k CCD.
Removing wrong lines from FITS images with MaximDL software
Please follow these steps:
Load the picture
Then use zoom from standard toolbar (400-800 %) you may also roll mouse wheel to zoom (maxim1.jpg)
From pull-down menu choose Process then Remove bad pixels... (maxim2.jpg)
Remove bad pixels windows appears
Choose an empty Bad pixel map
Mode: choose Column and click Use Mouse (maxim3.jpg)
Find bad column in picture and click on simply (be carefull it is more than one pixel wide often) (maxim4.jpg)
You will see in the box: "column nnnn" (it is the coordinate of the column where you clicked on)
If you have more than one bad column move the picture to next bad column and repeat mouse click (maxim5.jpg)
Finally click on Process button. (maxim6.jpg)
Bad lines will disappear and Remove bad pixels window will close.
Finally don't forget to save the picture.
