Learning planetary photography - session 7 (back to the QHY5III 462C)
I'm learning more about planetary photography now, including more about techniques and the software needed. I'm glad to say I'm less intimidated than before.
Last session I captured 1000 monochrome Jupiter frames using FireCapture's region of interest facility. This was more frames than I had before, but after speaking with some experts I realised I needed more still to keep the speckly "noise" down.
One expert suggested I use the QHY5III 462C camera, because it's less noisy, more sensitive and the pixel size was a better match for my equipment. As a rule of thumb, the pixel size in microns should be about one fifth your focal ratio. The pixels on the QHY5III 178M were a bit small.
I set up the Celestron 8" SCT and the saxon 2" ED Barlow on my NEQ6 as before, only roughly polar aligning this time. I was less concerned about the planet wandering, as FireCapture had a trick up its sleeve, which I'll mention in a second. I also used the IR cut filter that came with the QHY5III 462C.
I found Jupiter and worked on the capture settings.
I set the shutter speed to 9 milliseconds and set "autohisto" to 75%. This would automatically adjust the gain to keep the images neither under- nor overexposed. Rather than setting a region of interest, I used FireCapture's nifty "cutout" feature, which is similar, but the region actually follows the planet if it drifts, allowing you an even tighter crop. This increases the frame rate, giving you more images in the time available.
I took videos of 10,000 frames at a time (about five minutes) and saved them as SER files. Each frame looked like the screenshot here. It's not bad, but you can see from the histogram on the right it's a bit too green.
Back inside, I trimmed the videos to about 3 minutes to avoid motion blur. The cutout meant I didn't need PIPP to crop and centre the image, so I went straight to AutoStakkert, sifting and stacking the best 25% of frames.
Then I sharpened and recoloured in RegiStax. I'm pleased to say that while the Great Red Spot didn't put in an appearance, the final picture is another improvement, and I'm looking forward to more!