Help with first acquisition in many years. - Forums

Topic starter

Apr 30, 2021

First light with new ZWO Asi 294mc and Takahashi Toa-130, and would like it if someone could tell me what causes the 1. center circle artifact and 2. what's causing the stars to have the center bar looking artifact. This is my first light and it's only around 40min of exposure. I did darks and flats only but was also wondering why the starlink satellite trail in the upper left was still visible. Thanks for any help I haven't done this since around 2010 and have a lot to re-learn.

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andrea tasselli

Frequent contributor

Apr 30, 2021

There is just not enough information for a sensible answer I'm afraid. When, where, how long and how much. And then we would need to see the raw lights, the master dark and flat, what processing has been used and what program has been used and why colour is notably assent in a OSC image. This just for starters. The most likely explanation but in no way the only one possible is that the spot in the centre of the image is due to bad flat-fielding and the bar is due to thermals in the lens' cell.

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Lynn K

Apr 30, 2021

I agree with Andrea. Hard to tell. I agree the darker center is a flat calibration issue. The star trail was not totally eliminated because the stacking software averaged it in and did not see it as an outlier. What method did use to stack, average, median combine, signa clip etc..? I have had star spikes using a refractor. It is usually caused by the optics. It usually indicates something in the light path. A single element will cause spikes on both sides. Some optics or spaced using small rectangular spacers. They can intrude into the optical path. I had an W.O. & TMB refractors with that issue.

Lynn K.