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Hi Matty
As Dave (Gee) and Paul have suggested, I would aim for Ceres or Pluto to start with. I usually acquire the correct field of view by using a planetarium program such as The Sky or SkyTools, and then a GoTo usually places say, Ceres, more or less in the middle of the chip.
I pay a lot of attention to focusing the ‘scope. The camera control program, CCDSoft for the SBIG ST7, has a nice graphical display which shows me in real time when I have achieved best focus.
With the DMK, you can coarse focus on a mag 3 or 4 star and then try fainter stars as I have found that the fainter stars do not saturate the chip and turn blobby. Saturated stars do make it difficult to determine the sharpest focus.
I then take a 15 to 30 second image of the field that includes say, Ceres to confirm that it is the correct field by comparing the brighter stars to the FOV in say The Sky. I then make minor adjustments to compose the FOV so the object of interest is centred, or at one edge if it is moving quickly and I want to catch a trail across the whole frame.
If I take exposures longer than 60 to 90 seconds with the Vixen 4” refractor at a focal length of 918mm, I usually have to auto guide to keep the stars nice and round.
Good luck!
Dennis
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