02 Jun NGC 6888 – The Crescent Nebula
The image that destroyed my dreams….
It was June that made me finally decide that I’d made a mistake purchasing a non-cooled camera. As part of the processing stage, astro photography requires you to take several kinds of ‘calibration frames’ to deal with imperfections in your imaging train.
Dark Frames are exposures taken at the same length as your main ‘light’ exposures – but with the telescope covered. They’re basically used to build up a picture of the electronic noise generated by your camera, which can then be subtracted out of your final image.
The crucial thing here is that the dark frames need to be taken at the same temperature as the light frames.
With a cooled CMOS camera you can set the camera up inside, can cool it to a predetermined point (I use -10c for example) – you can then build a “dark library”.
With a non-cooled camera, you HAVE to shoot your dark frames at the same time as you main image – and you need quite a few of them – this means that with a non-cooled camera, I was spending upto 2 hours at the end of a session taking dark frames.
Time for an upgrade!
Scope: SkyWatched ED80DS Pro
Mount: SkyWatcher HEQ5Pro
Camera: ZWO 183MC
42x 3 minute exposures