SUMMARY The dark frame feature in the guiding module initially appears to work, but then after some minutes it will prompt me to capture another dark frame when one was just stored in the library. STEPS TO REPRODUCE 1. In the Guiding Module, choose dark frame. 2. Capture a frame 3. Choose a star 4. Click Subframe 5. Click Guide OBSERVED RESULT Ekos will prompt me to add the lens cover to capture a dark frame, as expected with an empty dark library. This dark frame is successfully stored in the library. Then guiding begins. After some minutes, Ekos will prompt for another dark frame. If we don't notice, it will wait 60 seconds then take a dark frame even without the cover on; this results in an obliteration of signal that causes guiding to fail. EXPECTED RESULT In a single guiding session where exposures and other settings are not changing, the guiding module should not prompt for a dark frame when a matching dark frame is already in the library. SOFTWARE/OS VERSIONS Windows: macOS: Linux/KDE Plasma: Stellarmate 3.5.2 (available in About System) KDE Plasma Version: KDE Frameworks Version: Qt Version: ADDITIONAL INFORMATION
KStars 3.4.3 experienced the same issue in the simulator -- but only one time. I had started guiding after deleting all darks from the library, so KStars correctly prompted me to take a dark. That worked fine, and guiding started. A minute later I switched into the capture tab and KStars prompted me for another dark. I had not tried to capture anything, nor did I change the exposure or gain settings in the Guiding tab or Indi control panel. This did seem better than Friday night, when I was prompted about 7 or 8 times for new darks before I just turned the feature off. I will try again when I can get a live scope set up outside, and will capture the guide log.
I believe this may be operating as designed. In the simulator tonight, I was able to reproduce the issue when I changed the temperature via INDI. Over the course of the night, cooling ambient temperatures will cause the camera temp to drop, invalidating darks in the library. Starting exposures can also cause the sensor temp to increase, having a similar effect in the other direction. There's no getting around matching your dark and light temperatures, but this is a real inconvenience. Over 20 minutes I had to put the cover on 7 or 8 times, and my temp threshold was set to 1°C. I wonder if there could be two settings for the dark library: a tighter tolerance for the cooled main imaging cam (0.5C, for example) and a looser setting (3°C, for example) for the uncooled guide cam. Would that wide range affect dark frame subtraction too much? In addition to the above idea, I would recommend allowing users to disable the auto-close option in the guiding module's "Cover the telescope in order to take a dark exposure" dialog. This way, the dark is not automatically taken when we're distracted in the field and do not put the telescope cover on. Some kind of persistent audio alert would be great, too -- to call attention to the issue in case the user is sleeping, working on another scope, etc. I think this can be closed unless you think the above ideas have merit.
With Dark Library, this no longer happens.