Quote:
Originally Posted by Dennis
I have an ESATTO Motorised Focuser that has focus steps of 0.04 microns, so what I do is step the focuser in 1,000 steps at a time until the Bahtinov Spikes just appear OOF, then I note the Step Position/Count.
Next, I step the other way (out) until I reach a similar OOF position and note that Step Position/Count.
I then take the mid-point of these IN/OUT Positions/Counts and Go To that number, putting me in the middle.
Using a Tak Extender x1.6 on the M210, with my ASI1600MM, the Critical Focus Zone is some 840 microns and with a x2 Powermate it becomes 1300 microns which allows for quite a large tolerance. Using at x2.5 Powermate to give me 7,000mm would give a CFZ of 2,000 microns.
Calculator here:
http://www.wilmslowastro.com/software/formulae.htm
Cheers
Dennis |
That's a good way to do it if you have a very precise focuser. I doubt mine would cut the mustard given backlash as well but I like the approach by the numbers. I need to do it visually though because I have to tweak the focus during the session as well.
PS: according to the calculator my CFZ is 3594 microns