What's best for MN-76 collimation?

Started by mskulick, 08/20/2007 04:38AM
Posted 08/20/2007 04:38AM Opening Post
Hello, everyone. I recently acquired an MN-76 and am wondering what to buy for use as a collimation aid. Orion has a "LaserMate" and an "Orion collimating ep" which is described as a combination sight-tube and Cheshire eyepiece. Or something else?
Any specific advice or direction would be appreciated. grin
Thanks for reading and...
Kind regards,
Mike.
Posted 08/21/2007 07:08AM #1
I find a laser that projects a crosshair pattern with
tick marks to be especially useful for collimating Mak-Newts.
Something like this device
http://www.buytelescopes.com/product.asp?t=&pid=5278

The "tricky" part is to make sure the primary and
corrector plate are concentric. The tickmarks on the
LaserMax cross hair pattern are very useful for this.
A sight tube can also be used, by making sure you can
see the edge of the corrector all the way around.
Posted 08/25/2007 06:43AM #2
Hi Michael-I've had several of these scopes up to and inclding my current MN-86. I'm very familiar with them and have totally rebuilt 2 of them. The laser collimaters that I've tried have been a waste. Any mis-collimtion of the collimater, itself or any wobble in the eyepiece holder throws it off commpletely. The Cheshire is still the most reliable up to a point. On the MN-76 get it as close as you can and then have a friend help to fine tune it on a fairly bright star with a 12mm eyepiece. I then slowly bring it into focus, watching that the "donut" hole disapears concentrically into a nice fine star point with no flares. Be sure that the OTA has totally cooled down (usually about an hour) or you will not be able to acheive good final collimation. Be patient and you will be rewarded by an excellent performing scope. Also be certain the diagonal is perfectly aligned with focuser. You should be able to observe a very nice concentric image of the diagonal mirror. (not oblong). Every one I've had, I had to tweek a little. If you think you have to, be careful not to scrath the miniscus lens. This really isn't as complicated as it may sound, and you won't have to do it very often unless the tube gets jarred or bumped. Good luck. Enjoy