Collimation will be OK in this case, only if the laser hits the optical
center of the main mirror. This is very critical (very small tolerance) for
fast mirrors.

--
Jan
http://home.wanadoo.nl/jhm.vangastel/


"Andrew" schreef in bericht
om...
Hi,

A quick question about collimation. I have an 200mm Newt, that was
unfortunately knocked off the mount a couple of nights ago. As soon as
picked it up I could see that the collimation was now miles off. The
only way I could get it back to approx. collimation was to use a laser
collimation tool. As I put it in and peered (carefully) down the tube
I was amazed to see the beam clearly hitting the main mirror and then
reflecting back towards the secondary (as a more 'fuzzy' beam). I
guess this was to do with the dew...

After a bit a fiddling with the collimation nuts I got it so the laser
beam left the collimation tool, hit the centre of the secondary, then
hit the centre-spot of the main mirror, and then reflected back to the
secondary directly along the path of the beam going from the secondary
to the main.

As far as I could work out, I figure that this must be collimated
since all the optical paths are aligned - is this true ?

Many thanks

Andrew

P.S. I didn't do a star test since I can never make head or tail of
them anyway - they always look fuzzy to me !!!