When things go too well ... at first. Vela supernova remnant.
Do you remember those old TV westerns where the hero whispers "it's quiet... too quiet"?
During the Easter break, I went to the dark sky site to photograph the Vela SNR (that's supernova remnant, not signal-to-noise ratio). This fibrous structure shows well in Oxygen and Hydrogen, but I don't think there's much Sulphur, so I decided to do a bicolour image.
Things went swimmingly. I'd polar aligned, centred on the target, and taken a couple of test images through the two filters before it got properly dark. When the time came, I chilled the camera and began taking images. Guiding was going well, and a meridian flip went flawlessly.
After this, it was about five hours of just steady as she goes. During that time, the rig would refocus every hour and change to a Hydrogen filter. I didn't have to do anything until about 3:30am when I would cover the scope for calibration photos. It was going so well I decided to retire to my tent.
I woke up to find the telescope pointing at some trees. I expected this. But what I wasn't expecting was that there were only 22 exposures in the computer. It turns out that, possibly only minutes after I'd left, the connection to the mount had thrown an error.
After every exposure, the mount "dithers". This is a tiny slew in a random direction which improves the image in a couple of ways - it's a story for another time. The error had happened while the controlling software was waiting for the guiding software to report that it had finished dithering, and the message never came. The computer simply waited for the next five hours. The problem was fixed with the touch of a button, but I'd lost all that time.
So here's the 22 exposures stacked with dark, flat and bias calibration images. It's monochrome, of course, as I only got one filter.
So that's the image I have. I was busy the following weekend, and after that It was too late in the year to have another go.
But, life is long and the stars will still be there next year.
Update: I went back a fortnight later and got just enough time on the target to do a half-way reasonable bi-colour image.