I have seen some autofocus routines, but none work as well as using a
diffraction focusing tool or a Hartman mask. Part of the problem is that in
order to use the FWHM you must look at several exposures to average out
seeing. This is especially true as you approach good focus as the FWHM will
move around a lot.

With a diffraction focus tool and APT's control of electric focus (it allows
focus goto's and only requires minor touchups after that) I can regularly
get perfect focus in about one or two minutes so I have not bothered looking
into it further.

Blair


----- Original Message -----
Sent: Tuesday, March 20, 2001 4:59 PM
Subject: [M]: 216XT CCD autofocus ?


> I currently achieve focus for my CCD images the hard way by using masking
> tape etc. and have created a parfocal eyepiece. I have read recently that
> there are automated ways to achieve a good focus using a combination of an
> electric focuser and software to analyze a star's Full Width at Half
Maximum
> (FWMH) value but wasn't sure how well this worked in reality and what
> software packages can really do this? Pictor 7.13 does graph this FWMH
> value using the autofocus feature but I don't currently have the 2nd
serial
> port to test out this functionality further.
>
> Prior to me investing in electric focuser, extra serial port and
potentially
> software (if Pictor doesn't do it), does anyone have any experiences in
> achieving true autofocus.
>
> Many Thanks,
>
>
> Chris
>

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