Hi Matty
For Pluto, the details are:
Vixen 102mm f9 refractor.
SBIG ST7E CCD camera.
5 x 5 minute exposures.
So, on 21st August I captured 5 x 5 minute exposures and stacked them together to give an equivalent single exposure of 25 minutes. I did the same thing on the next evening and then animated the two images to show the movement of Pluto against the fixed stars.
Why did I take 5 x 5 minute exposures rather than a single 25 minute exposure?
- If you make a mistake with a single 25 minute exposure, you loose the lot all in 1 go.
- If you make a mistake with one of the 5 x 5 minute exposures, you only loose 1 sub-frame.
- To auotguide a single 25 minute exposure is much more difficult and demanding of the mount and guiding system than auto guided a 5 minute exposure.
- A 25 minute exposure would have saturated the brighter field stars, causing blooming.
- If an airplane or satellite passes through the field on 1 of the 5 x 5 minute exposures, you can erase the trail by doing a median combine of the 5 frames, which would reject the trail.
Eris was captured using my Celestron C9.25 with the Celestron F6.3 Reducer /Corrector. The exposure was 10 minutes and I captured between 3 and 5 sub-frames for the 4 day sequence.
To whet your appetite, here are another couple of examples of using this technique. I’m not sure of what mount/scope combo/type that you have, but I’d try for sub-frames of at least 3 minutes with the DMK and see what results you get.
Cheers
Dennis