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Automating Focus Star selection

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Hi People,

What does a focus star look like?  I have a Newtonian F/5 200mm/1000mm plus a Canon DSLR and I'm trying to autofocus.  I'm thinking 15 secs on a Mag 6 star at ISO 1600 is good and then an HFR calculation what do you think?

Up until now I've been maually selecting the star in advance, but sometimes I forget to check the Dec, or RA and for large constellations these can be below the horizon (this is usually sub-optimal 🙂).  So I'm thinking a little SQL and selecting DEC of DSO target +/- 10 degrees and RA of DSO target +/- .5 hrs and Mag 5.5-6.5 for the focus star.  I then loop round, adjusting the fine focus programmatically until the HFR is a minimim.

Will this work?

Kind regards


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