Sorry, I do not have a specific answer but just some hint on where to look.
From the spec
Surrounding the periphery of the device is a border of light shielded pixels creating a dark region.
Within this dark region, exist light shielded pixels that include 20 leading dark pixels on every line.
There are also 20 full dark lines at the start and 9 full dark lines at the end of every frame.
Under normal circumstances, these pixels do not respond to light and may be used as a dark reference
This 'overscan' may be ignored or used by the camera hardware or driver (some camera do their own 'dark compensation' which then conflicts with our preprocessing, this is mostly entry level or consumer oriented devices). It may or may not be saved with the image. If the image you get is 4096x4096, then the prescan area is cropped by the camera (this is usually the case by default) and you cannot use it in PI. You may be able to find a way to persuade the driver or your acquisition program to save the prescan area, but not all camera/drivers supports this. I am afraid that you will have to check with SBig or on their forum, as this is independent of PI.
You can check if your are successful by looking at a flat, it must be larger than 4096x4096 (see the spec for exact size) and must have a black border. Otherwise there is no overscan in the image and nothing you can do in PixInsight.
Please report if you have any success to find the overscan, i would like to add some information on the subject to the ImageCalibration documentation.
-- bitli
