Re: ATM collimation bolt lenght

["Bill T." <twentiethwave@hotmail.com>]

Jan van Gastel wrote:
> I am going to attach collimation bolts to the bars of the mirror cell. How
> much travel should they have? At first I was thinking of 10 mm (0.4 inch)
> upward and 10 mm downward, so 0.8 inch total travel. But now I think this
is
> way to much and 5 mm (0.2 inch) up and the same for downtravel will be
> enough. What shall I do?

Jan,

Once you've got the collimation bolts close to their normal position, the
total day-to-day travel variation for collimation will be no more than 1 mm.

The main case for longer travel is:

--If the mirror cell support is not perfectly square to the optical path,
you can comnpensate with extra bolt travel during initial setup.

--Extra travels gives you the ability to make slight adjustments in the
focal plane plane position, without having to trim tubes or add spacers.  I
recently bought an eyepiece that required several mm more "in" than my
previous closest eyepiece.  I was able to accomodate it by simply lowering
all the collimation bolts in proportion.

I usually allow +- about 7 mm from the expected center position.

Bill T.