How should I focus - FWHM/Bhatinov/Both??!

[Johnboy2011]

So, I'm all set up for the third night on the trot and the clouds have turned up again, I must be very patient!

Having just downloaded the full version of APT I notice the FWHM focus aid is available, is the way I should be doing it? I see it mentioned regularly by people who know what they are doing and I'm thinking that will do me!

If I use it I guess I don't bother with the Bhatinov and just use FWHM on one of my alignment stars?

John:icon_scratch:

[ollypenrice]

I use a Bahtinov to get very close but do tickle up the final focus with FWHM. However, I have a very good observing site and experienced imagers based in the UK seem to agree that the seeing is too bouncy for FWHM to work well. A Bahtinov suits the conditions better, they say.

When I use FWHM I work unbinned and in subs of at least three seconds. This allows the seeing to average out.

From what I gather, though, in the UK stick to the Bahtinov. They are brilliant things.

Olly

[Johnboy2011]

Thanks Olly.