On Sunday, after a day of solid rain, there was a little window of a couple of hours of clear sky. I’m currently working through my old DSLR lenses at the moment to try to work out which ones are any good for Astrophotography- and on Sunday it was the turn of my “Nifty Fifty”. For the uninitiated- these are 50mm prime lenses that are very simple and at the budget end of things (the going rate on ebay is £20-£40, I don’t think I paid any more for mine more than a decade ago), but which will return very sharp images and can open right out to f1.8.
Altogether it was slightly challenging- focusing was very tricky so I stopped it down to f3.5- and even then just a mm or 2 out on the Focus Ring (which feels like it was made by Fisher-Price) and the stars turn into bloaty pentagons (the lens has a 5 bladed diaphragm) that DSS stacking software refuses to recognise. The temperature was below dew point which meant that the lens misted over every few minutes (and there’s no lens hood); and each time I wiped it I had to reset the focus, which would then take 2 or 3 frames to check and correct. I then found that, although at that focal length I can track almost indefinitely without guiding, the light pollution was fogging me out after just 2 minutes. Still, after an hour I had about 30 minutes worth of data which would hopefully be enough to see if the lens is worth persisting with.
Unfortunately, distracted by the various issues I didn’t put anywhere near enough effort into framing. My plan was a field of view like this, that would put M31 next to our Milky Way and get a bit of colour from Pac Man and the brighter stars in Cassiopeia, plus the clouds of the MW:
Instead I had M31 too near the centre of the frame, and because of some nasty light pollution issues in the bottom right hand side had to crop anyway. This is the final result:
Although the plan didn’t really work I quite like it- it at least shows the isolation of this vast object and also that the lens works OK once you get used to working with its niggles. I think I’ll try this again in a month or two when M31 is a bit higher in the sky and away from the light pollution. I was also thinking of trying a hair-dryer gently on the lens every few frames to keep the dew at bay. Hope it doesn’t melt the plastic!