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BAA Images Grant Privett

Observation by Grant Privett: Satellites

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Grant Privett


Grant Privett


2021 Mar 06 - 22:40


2021 Mar 08 - 15:23



  • SkyWatcher 114mm f5 Newtonian
  • Starlight Xpress Lodestar
  • NEQ6 + Rowan upgrade

30s x10



Target name

Rosette nebula



About this image

It was a silly idea imaging a  big object with a scope with a wobbly focuser and a Lodestar but it was just a bit of fun. When I came to reduce the images I found I had captured lots of satellites over the course of an hour or so. Here they are shown. Looked like about 5% of my images had one. Yeah, median stacking helps but bright ones often leave a low level residue that takes lots of frames to eliminate entirely.

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Nick James
Nick James, 2021 Mar 08 - 21:38 UTC

Sigma clipping is a lot better than median stacking and it effectively removes bright trails too since their clipped pixels do not bias the mean (medians are statistically horrible in this context). I have found this very effective on stacks of 30 frames or more. It is occasionally necessary to delete a frame altogether but this is much more often due to aircraft than satellites. CMOS cameras help a lot since you can take a lot of short frames with minimal dead time and read noise.

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