#AskPS: How can I find focus with a DSLR and a Dobsonian?

Funny you should ask!

Yes, I had issues finding focus because DOBs aren’t generally set up for prime focus AP, and often require the sensor to be closer than the focuser allows (not enough “in-focus” distance).

I figured out that using a coma corrector for newts, (like this), the problem is solved with only 0.1x mag. It gave me about 10mm or a little more “out-focus” distance that was perfect for my old Zhumell 10″ Dob.

For planetary use, I used that same Dob and EQ platform, but only with either 1 or 2 Barlows, excluding the coma corrector. There was plenty of focus distance with that setup.

Cheers,
Cory