ASTAP plate solve failing bin2 but working bin1

[lowenthalm]

I saw a similar problem of plate solve working at bin 2, but not at bin1 back in April in the logs, but this seems different, as it has only started for me when I started using 4.1.10700.0.

I have a 2800mm focal length Edge 1100. Pixel scale is .34 arc seconds for a 4144 x 2822 ASI 294 Pro Cooled camera (4.63um pixels).

I was having pretty consistent failures (9 out of 10) for bin 2 plate solving using ASTAP using 3 second exposures at 320 gain with the correct dark and flat applied. On a lark to change a variable, I switched to bin 1, again applied the correct dark and flat. Plate solve works every time now. I have 8-bit images for plate solve turned OFF and the Focal length set to always use 2800. No custom ASTAP command line options are set.

Just to add a little spice to the problem, sky background is fairly bright with the near full Moon, but I have been 45 degrees or more away from when this happened. I have a dew cap on, so the scope is fairly well shaded from the glare. Still, I suppose its possible that this is due to the Moon brightening the sky, rather than a change in this version of Sharpcap. It seems to me that the bin settings shouldn't make a difference.

[admin]

Hi,

so, based on feedback from other sources (and some guidance from Han, the author of Astap), I have just changed from sending a debayered PNG file to Astap to sending a RAW FITS file.

The problem being addresses was that under some conditions, hot pixels in the RAW image were becoming small clusters of brightness when debayered, which were then detected as stars by ASTAP. I am also thinking that it is possible that Astap may not have been reading 16 bit data correctly from PNG files, but that is not certain.

It may be worth specifying "-z 2" as an additional option to Astap to see if that helps (in the SharpCap plate solving settings). For high resolution images, Astap will automatically reduce the resolution using binning, so that may work for Bin1 and remove the bayer pattern. For bin 2, the lower resolution may fail to trigger Astaps automatic reduction in resolution.

cheers,

Robin

[lowenthalm]

Aha. Makes sense. Crossing fingers. It works so well when it works! ASTAP is still the best local plate solver option I have tried so far, despite the problems.

Luckily, seeing is really good now, so I have been running mostly bin1. I just ran into it because I use bin2 when I am star aligning my mount.