| Telescope | CTIO Curtis Schmidt |
| Date | 3/8/1999 |
| Instrument | Tek 2k #2 |
| Filter | Sloan r' |
| Exposure Time |
900 s |
| Other | Image not processed. |
Problem:This stellar ghost image just to the top right of M83 (the galaxy) is a feature frequently encountered during observing runs with Schmidt telescopes. It normally does not occur with other telescopes. What happens is that light from a bright star in the field reflects off the primary, then off the Schmidt corrector plate, then off the primary again, then to the secondary and detector. The "stellar ghost" always appears diagonally opposite about the center of the field of view from the offending star. Its shape may vary depending on the Schmidt and filter used, but the feature is common to Schmidt data. |
Fix:Tricky. If you take several images of the same field, you could dither very little between frames and hope the ghost doesn't move much, so that it is easily identifiable and well defined in the final combined image. Alternatively, you can try dithering by a lot to move the offending star around and then hope the ghost image changes position enough that any transient features are removed when median combining the images later. |
Look at another Stellar Ghost image
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