FWHM doubles

[MikeB838]

Hi Robin,

I'm fine now with the "new" FWHM-values in SC 285, thanks!

cheers,
Mike

[lowenthalm]

Are the FWHM values now always reported in bin 1 pixel units? I need to turn off guiding while running my focus subroutine, so I do multi-star focus at bin 2 to reduce the effects of no guiding. I observe that as of the April SC updates, the multi-star focusing reports bin 2 FWHM having roughly the same values as live stacking does when I subsequently start live stacking at bin 1. In previous SC versions, bin 2 showed about half the FWHM that I would see at bin 1.

[admin]

Hi,

there's no code to try to make the FWHM get converted to bin1 pixels, so that's not expected behaviour. Do you see the same if you flip between bin1 and bin2 while using the MultiStar FWHM focus tool?

cheers,

Robin

[lowenthalm]

Interesting. I have observed this apparent behavior when running MultiStar FWHM focus via scripting (as described in my initial post here) using the 4.1.13251.0 release, but not with the 4.1.13131.0 release (which was the previous version I was using).

In the script, there is a SET PLATESOLVE/FOCUS SETTINGS EXPOSURE 5 followed by a PRESERVE CAMERA SETTINGS before changing binning, flats, darks and going to full frame size before performing the MultiStar FWHM focus, with some of these operations are performed with some Python script calls. I did check to make sure the camera was actually set to bin 2 when one of these focus scans was running, and it was showing bin 2 in the SC GUI as I expected. There is a chance I may possible I have been misunderstanding what I was seeing on the screen in some way, or the FWHM in guided bin 1 live stacking and the FWHM in unguided bin 2 MultiStar FWHM focus happened to be similar.

Its probably not worth your time to look into it if no one else is reporting this. I won't have sky for more than a week due to bad weather, but will observe this more carefully during my next observing session and I'll report back what I find.

[admin]

I will also have a look the next time I get a chance - see if I see the same.

cheers,

Robin

[lowenthalm]

For the last week, I have been testing the 64-bit version of 4.1.13360.0 with my Celestron Edge 1100 CST on a CGX mount.

I believe all is ok after carefully monitoring the behavior of the FWHM in multi-star focus sweeps in bin 2 compared to the FWHM observed in bin 1 RAW subs captured with live-stacking.

I may have got myself a little confused during some nights with not-so-great seeing and/or on-and-off wind. This introduced a lot more noise than normal into the FWHM measured in unguided bin 2 focus sweeps compared to the FWHM observed in subsequent guided bin 1 live-stacking runs with which I collected my raw subs.

[admin]

Hi,

thanks for the report - I also did a test when we had some clear skies a couple of weeks back and I saw pretty much expected behaviour - changing to bin2 didn't quite halve the FWHM, but certainly dropped it down towards half of the bin1 value.

Let's assume this is closed now unless someone comes up with new evidence to the contrary.

cheers,

Robin