Issues with Altair 26C camera

[IDM]

Hi,
I have been using Sharpcap version 4.09538 with my Altair 26C but recently have been having loads of problems. The camera loads fine and can be focuseer assistant works as well as the polar alignment. However, plate solving has stopped resolving and I can get messages such as unable to solve or too many stars (even when the gain and exposure are ludicrously low). I see that version 4.09538 is now available will this solve the issue? I am trying to discern if I have a software or a hardware camera issue.

Also whilst I know the smart histogram is the best way to go but do you have any recommendations on the likely best settings for this camera in particular I am struggling to work out the best black level to use. I did do sensor analysis using the 4.09538 version with the results below. Any help or thoughts gratefully receive

[admin]

Hi,

there are no significant changes relating to plate solving in the recent updates of SharpCap 4.0 - almost all the changes have been updates software from camera manufacturers to support new models.

If you are getting messages about 'too many stars' even with low gain/exposure, it probably means that the plate solving application is picking up noise in the image as stars. The most likely cause of this is the 'sigma' setting in the SharpCap plate solving settings being set too low. Sigma is a measure of how significant a bright area in the image has to be to be counted as a star, and with a very low value any random fluctuation might be picked up as a star, giving hundreds or thousands of fake stars.

As to the best settings for the camera , the simplest approach is to use the SharpCap smart histogram function, which will measure your sky brightness and produce a customized recommendation for your conditions based on your sensor analysis results - see https://docs.sharpcap.co.uk/4.0/#The%20 ... n%20Window

In more general terms for this camera, set 300 gain and an exposure that is at least 15s but not long enough to get you guiding/tracking issues. Set the black level by taking some dark frames and adjust the black level up until there is some clear space between the bump in the histogram and the left hand axis of the histogram graph.

cheers,

Robin

[IDM]

If you are getting messages about 'too many stars' even with low gain/exposure, it probably means that the plate solving application is picking up noise in the image as stars. The most likely cause of this is the 'sigma' setting in the SharpCap plate solving settings being set too low. Sigma is a measure of how significant a bright area in the image has to be to be counted as a star, and with a very low value any random fluctuation might be picked up as a star, giving hundreds or thousands of fake stars.

I have two telescopes with mini pc's both operating identical software. The one with a Zwo ASI294 MC pro has an ASTAP sigma value of 61559 and behaves faultlessly. The second scope has the Altair 26C and the ASTAP sigma value is 61.561. So from that I guess its not the sigma value that is the problem. I have a suspicion that the camera is misbehaving as it used to work but now is giving very odd results in that it wont platesolve and the calibrated stacked images don't look right. Does this sound like a logical conclusion?

Thanks in advance.
Ian

[admin]

Hi Ian,

the 'sigma' setting I was referring to is for Astrotortilla (and ASPS/Ansvr), not Astap. If there is a sigma in Astap then it is probably not the same setting. Anyway, the value for AstroTortilla is usually between 20 and 100 or so, not in the thousands, so it must be something different.

Often a good check on plate solving is to save an image and upload it to nova.astrometry.net (online plate solver). If that solves the image then the problm is (most likely) an issue with your software settings somewhere. If that fails then the problem is likely with the image data (not bright enough, not enough stars, etc).

cheers,

Robin

[IDM]

Oops that my bad I missed the decimal point for one of my numbers!! One computer has a sigma of 61.559 not not 61559! I managed to get the scope to platesolve last night and am just in the process of taking calibration frames to see if all is well or not.

Many thanks,
Ian