Quote from: Pema on February 18, 2026, 05:05:27 PMWhen you do those super-long exposures, are you there the entire time, or can you leave it unattended?
If things go well, I am not there for
any of the time. The observatory is set up for remote operation. I do all the targeting setup from my home office. I click the GO button, then I go to bed. In the morning, hopefully I wake up with a pile of image files to process.
Quote from: Pema on February 18, 2026, 05:05:27 PMWill your dome close on its own?
Yes. That is an extremely important part of the observatory systems. The dome has its own controller. At the end of an imaging run, the imaging software will tell the dome controller to close the dome. The dome controller can also close the dome on its own initiative if it detects rain, if there is a power failure (it has battery backup), or if it doesn't hear anything from the imaging software for a minute.
Quote from: Pema on February 18, 2026, 05:05:27 PMAnd when you do very long exposures, do you have to span multiple nights?
Yes. My longest total exposure time on one target was 22 hours. Obviously that can't be done on one night. In fact, each exposure in the Sh2-284 image was 5 minutes or less. You don't want long exposures because if something goes wrong, you want to be able to throw away one or two without affecting the total time very much. This image was made from 143 images taken over four nights.
Quote from: Pema on February 18, 2026, 05:05:27 PMIf so, is the targeting precise enough to align things, or does the processing software take care of that?
Yes, the software re-aligns the telescope for each night. The telescope mount can get to a target within a few arc minutes. However, even the most accurate mount can't centre the target accurately enough for photography. The software compensates by a technique called "plate solving". The software takes a picture, scans it to find the patterns of stars, and then looks for those patterns in a database. It calculates where the scope is actually pointing and then computes what adjustment is needed to centre the target. With two or three iterations of that process, it can re-centre the target within 50 pixels, which is next to nothing.
The processing software adjusts for those few remaining pixels of error, and crops off any resulting ragged edges.
Quote from: Pema on February 18, 2026, 05:05:27 PMWhat do you do about satellites?
The fact that I take multiple short exposures allows the software to remove satellite trails.
Quote from: Pema on February 18, 2026, 05:05:27 PMCan you do infrared, or is there just too much ambient?
I don't do IR myself. The closest I get is Hydrogen-alpha, which is very deep red. It is close enough to infrared that consumer cameras have to have their IR filters removed to capture it, but it is still visible light.
Quote from: Pema on February 18, 2026, 05:05:27 PMDo you know what made that M13 image turn out so well?
Luck, mostly. Atmospheric conditions were excellent, and my equipment worked perfectly that night. In processing, I saw that it had potential, so I was very careful in my adjustments. I made lots of very specific, very tiny adjustments until it looked right. When the final tiny adjustment made everything "pop", I had the good sense to stop and save the file.
Quote from: Pema on February 18, 2026, 05:05:27 PMIs the software able to correct for atmospheric effects?
Nope. If the seeing is poor, there is nothing you can do to fix it. If the transparency is poor, you can shoot through narrowband filters to remove some of the light pollution, but you can't add light that isn't making it to the telescope.
