Learning planetary photography - session 4 (at night!)
I'm continuing to learn about planetary photography. I'm a beginner here too, so you can do this!
Last time, I showed the first few days of work with a couple of our new QHY cameras. I'm totally new to this, and spent the first few sessions just taking test shots during the day. By my fourth day, I thought I'd take it out at night.
I had a 8" Celestron SCT on my NEQ6 mount, and a Barlow for a focal length of 4064mm.
Behind that, I had a QHY5-III 178C. This is a colour camera, with very small pixels - they're 2.4µm. This means that while they're not very sensitive, they're packed in tightly so you can get the most pixels on the planet.
I was using the "lucky imaging" technique, where you take as many images as you can, and sift through them, selecting and integrating the best ones. The atmosphere is a chaotic place and randomly forms lenses of different temperature air. Some of the short photos should be able to fluke good views - I hoped.
To get the highest number of images I could, I cropped the sensor down to a "region of interest". Having a well tracking mount helped a lot here. Previously I'd had trouble with a go-to alt-azimuth mount, with the planet wandering all over the place.
I took two sequences of Jupiter, with exposure times of 30-40ms. I processed with PIPP, AutoStakkert and RegiStax (more about that another time).
The photos are bright, with little noise (which shows up as speckles over the image). But they're blurry. I don't think it was focus (I was careful about that). Rather I think it was "seeing" - the atmosphere changing during each exposure, rather like motion blur.
You can also see I had trouble with colour balance, the two Jupiters being quite different.
More problems to work on. I did what you all should do - asked an expert. They advised me to shorten my exposure to under 10ms and compensate with gain. This would help with the motion blur problem. Colour balance can come later. One thing at a time.