Re: ATM Collimation Question

[Brad Davy <bdavy@fred.net>]

To all the well meaning people who sent detailed instruction on how to
collimate, thanks.  For the record, I had already accomplished all the
steps to collimate without using the star, except using a laser (I'm
trying that tonight).  Given that this is a fairly fast instrument, its
the star test collimation that is the focus of my question.

I now believe that the secondary may be off by just a few millimeters,
so I'm going back to recheck that, then do the laser alignment.  As I
understand it now, I'll just adjust the primary with the star test,
using the shadow of my hand in front of the OTA to indicate which
direction adjustments need to be made.

Regarding Jims comment on the precision of the laser, it is interesting
to note that the laser only checks the very center of the mirror, and is
only as good as your ability to determine that center (physical).  The
star alignment checks the optical center, which I suspect, especially
for amateur mirror, may not be coincident with the physical center (and
may be the root of my current problem!).

Brad
bdavy@fred.net               http://www.fred.net/bdavy/home.html
bdavy@nox.cs.du.edu