Proposal of a "Quadratic Fit" Auto Focus evaluation method

Sequence Generator Auto Focus
9

Gabe,

I do think that some value can be added in going further away from focus though.

As I already wrote, SGP didn’t manage to detect stars when I went beyond +/- 670 µm away from best focus. However, in order not to compare apples and pears we must define “near focus” and “further away from focus” in relation to the CFZ of the respective scope. There are different formulas for the calculation of the CFZ though, but it doesn’t matter: CFZ is proportional to (f-number)^2. So the values in the following table correspond to my max. distance away from best focus of 670 µm:

f-number   max. distance from 
    	   best focus [µm]
     4		 430
     5		 670   <==
     6		 960
     7		1300
     8		1700
     9		2200
    10		2700

I would like to hear about which max. distance away from best focus at which f-number people are using. Then we can discuss further, whether my set-up and my adjustments are wrong for SGP’s AF evaluation and impracticable for people using other scopes.

I want to add that in the other thread,

I got a response from one forum member who also sees parabolas, namely with his SN 10, thus a Schmidt-Newtonian:

Bernd