Re: having guiding problems


Ray Gralak <rgr@...>
 

Hi Roland,

If you want to reduce periodic error just for the fun of it,
then by all
means do so. Just do it and see what your results are.
I've experimented with various levels of periodic error in my 1200GTO mount
(not only did I reduce PE but I made it artificially higher for testing by
loading an appropriate PE curve). Using a 5-second autoguider cycle just by
turning on PEM reduced FWHM by 0.15 arc-seconds when going from 3.0 arc-sec
PE to 0.5 arc-sec . The stars looked just as round in each case, but the
FWHM of the stars with PEC on were tighter.

Also, for those autoguiding through a narrowband filter with an SBIG camera,
good PEC is critical. It will allow you to increase the autoguider exposure
time to get a guide star through the narrowband filter.

-Ray

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