Finding an item in a bright/dark background

When one is confronted with images that are very difficult to analyze because the background is very bright or very dark as is usually the case for images taken in space from say star trackers, one should look into using the AVIS FITS viewer. By playing with the lower and upper threshold of the histogram toggle, one can pretty much isolate interesting component that are a little bit above the background.



This is how we evaluated some of the images we gathered from Starnav 1.



After receiving the first images from Starnav 1, we figured that most of the surrounding of the camera was shining too much light into the camera. After going through the AVIS viewer and playing with the filter threshold, we could find other unknown things being in front of that camera (item B and C).




Item B was very difficult to find because it was really only a few pixel above a certain background and one had to remove brighter area around it. Only then, one could see the round shape of it.