collimation using a planet or by iterative method??

Alvin Wibowoo posted:

Like many fellow SCT users, when it comes to collimating on a star, the
process is anything but simple.

Once a person becomes familiar with the process of collimation, it becomes
very straight forward and fairly easy. You need a star (Polaris can be a good
one) and a quality high-power eyepiece (yielding at least 25x to 30x per inch
of aperture). If you are out of collimation, star images at high power will
tend to look somewhat elongated (almost shaped like a diffuse cone). Center
the star and look at the image to carefully note which direction it appears to
be flaring towards (ie: the broader portion of the elongated star image).
Then start adjusting a screw on the secondary until you find the one which
makes the star appear to move in the field of view in the direction of the
flaring. Center the star again and adjust the screw to move that star again
in the direction that it is flaring, and after a while, you should see the
flaring become less and less as you repeat the process. Eventually, the
star's image should look fairly round or symmetric. When that happens, you
are collimated. Remember that if you wear glasses to correct astigmatism, you
should leave them on while doing this. If you can't get good collimation
after trying this process, then there is probably something wrong with the
instrument. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************