JuergenN replied to the topic 'Guide Star SNR zero...' in the forum. 2 years ago

Yesterday I played around with the SEP parameters. It was ambigous. Most of the time it worked well, but sometimes e.g. the choice of the guiding star was questionable (at least for me). I missed to take pictures, sorry. Example: I had a field of stars which are good visible, smaller ones and bigger ones. What was choosen? A hot pixel, I had RMS 0.02 ;-) also it found many companion stars and linked them. The min area was set to 6 Pixel (even if I set the star filtering parameter "min size" to 2px)... When set min area to 10 Pixel a "normal" star was used as guiding star.
I also tried to click on a star, then this star was used as guiding star one or two steps, but then it switched back to the hot pixel...

I used the SEP profiles "Guide Default" and AllStars, where "AllStars" seem to slow down the system when there are many stars in the FOV.

I also tried to find out, what the different parameters mean and read the linked pages. But its hard to understand, at least for me. Some parameters seem to be clear but if changing them it gives weired results (like the "Hot Pixel" with min area 6 pixel).

Am I right to say that
- the Sextractor-parameters are for choosing the guiding star? Or for guiding star AND companion stars?
- the Star Filtering Parameters will search for any stars in the FOV within the parameters?
- The guiding star and the companion stars are choosen out of the "Star Filtering" stars (which should be clear I think)

I hope I'm not bothering you but I want to understand what I'm doing here ;-)

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