I did not use flats. I just used bias and darks. Also just prior to this I imaged pleiades and these artifacts were not there. In between though I placed the tele cap back on to do the darks though. whats weird is that the three slashes are exact duplicates in the top and bottom right sided ones.
Would dust motes do that? the same ones show up in different places on a single photo?
thanks for responding AZ
First step is to use flats. I gotta agree with that.
As for the Pleiades.....it could well be that these artifacts were there, but not visible. Remember, M42 has a lot of nebulosity. Pleiades has some, but mostly blank sky, which may not be affected as much.
The duplicates are very similar....but they are not identical. (I selected an area around one, and tried to paste it directly over the other spots. Close match, but not perfect even after translation, rotation, and scaling.
Remember, when we say "dust" we mean dust, pollen, ash, sand particles, Covid-infected sneeze particles, flecks of paint, and anything else that gets on our optics. Could it be an insect left footprints of approximately the same shape as he (or she) walked across your optics?
I'm still with the flats thing.