cosmic ray detection in dark frames
cosmic ray detection in dark frames
Cosmic rays can be very annoying also in dark frames. The problem is that they might cause changes in the counts in the subtracted dark frames. We have now a cosmic ray detection mechanism that is about to be completed. This mechanism can be used in order to eliminate cosmic rays not only from the light frames but also from the dark frames. This might give a more accurate pixel counts and a better luminance change detection.
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nbrosch
- Ensign
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Cosmic ray rejection
Lior, the cosmic ray (CR) problem is well-known in CCD astronomy. IRAF has a task called CRREJECT that you may want to look to. It is also possible to look for CRs by comparing a frame with the one immediately preceeding and immediately following it; this would flag one-frame transients and in most cases these would be CRs. You may also notice that most CRs tend to be longish streaks; these would be mixed up with meteors. The ONLY way I can think of that would really identify CRs is if you had two CONCAMs rather close together. Real transients and meteors would show up in both, but CRs would be seen in only one camera.
Noah
Noah
Comparing two frames might be effective, but as you mentioned, we might loose meteors. Since in most cases we can easily tell if a PSF is a cosmic ray hit or a true astronomical object, I believe this can also be done by machines. The current algorithm has a high level of accuracy (much more than 90%), and it is still not fully optimized so I assume we can get to almost 100%, without loosing meteors.