Re: [APML] Off Axis Guiding Help

[steve banbury <banburys@sonic.net>]

Eric Barber wrote:
snip

>
> I do have the Wil Milan and Jim Janusz tutorials printed out and dog
> eared. I have suspected that a focal reducer on the ST4 might help, as
> the stars on the pickoff prism don't look too bad through a 25mm
> eyepiece, but I hope to not spend that money right now.

snip

Hi again Eric--just a quick note about the stars and the pickoff prism.

If you have the pickoff prism located downstream (camera side) of a
focal reducer lens on the OAG like the f5 configuration for the
Lumicon GEG, the spherical aberration on the edges of the focal
reducer lens really messes up the stars.  Looking at them on the STV,
they all looked like little seagulls--and the autoguider choked on
"M" shaped stars.

Good luck--Steve


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