"Light ghosting" on brighter stars SBIG 6303e chip - CDK 20

The very bright stars are swamping the column. An excess of photons causing electron spill ;-) You can probably remove in post-processing.

 

It is called blooming. The KAF-6303 has a non-antiblooming sensor architecture. NABG has advantages in terms of sensitivity and linearity; unfortunately bright stars can develop these blooms.

What is happening is that so many electrons are in the pixel that they effectively neutralize the electric fields holding them in place (the CCD clock electrodes), and that allows them to flow along the column.

Some sensors have anti-blooming features. They bleed off excess electrons to prevent the blooming. It also has the effect of making the sensor nonlinear near saturation and the extra structures can impact the overall sensitivity a bit.

The options are either to reduce your exposure time and take more images (suffering some additional read noise contribution), or to cosmetically edit the images in post processing. MaxIm DL has a fairly effective bloom removal tool.

 

Please upload a FITS version of your image so I can give it a try.

 

Okay I have had mostly success with the manual removal. Auto did not work. The brightest star has an oddly discontinuous bloom; the tool cleans up the star but leaves a little tail behind. I would nip that off with the clone tool.


Manual bloom tool setup.

Resulting image.

See http://www.diffractionlimited.com/help/maximdl/Remove_Bloom.htm for detailed instructions on using the manual mode.

 

This is a characteristic behavior of the KAF-6303 with very bright stars. You will not see that occur with KAF-16803 or KAF-16200, which have overflow drains.

 

Your camera does not have a problem. That phenomenon is simply a characteristic of the KAF-6303. All 6303 cameras will do that.

Yes the 11002 will not do that, but it is also much less sensitive than the 6303. It will require much more exposure to achieve the same results.

I would recommend either the 16200 or 16803. Given that you have a longer focal length I would strongly recommend the 16803, because it has a larger pixel size that is better matched to your telescope.

 

AO-L is a very old model, designed for the STL cameras. We currently sell the AO-X. It's a very nice unit.

 

The 16801 is usually chosen by researchers who are doing surveys etc. They are looking for the maximum sensitivity and linearity and are no so concerned with cosmetic issues like blooming. It is also a windowless sensor so it has somewhat better quantum efficiency.

The 6303 is typically used for the same reasons; it is the more economical solution.

Given that you want large area and anti-blooming, the 16803 is the best sensor for your needs.