Mewlon 250 Collimation

Hi all,

I am having great difficulty collimating my Mewlon 250. The problem is that I do not know what I am doing - I do not know what the turn of each screw in each direction does to the secondary mirror.

This is unlike collimating my SCT, for which I used this very useful guide:

http://www.astromart.com/articles/article.asp?article_id=548

Basically the guide says to locate a 12 o'clock screw - which controls the up-and-down motion - and the other two screws control the sideway motion. Thus, by tightening say, the left screw, I know I am shifting the secondary shadow leftwards.

The problem with the Mewlon 250 is that I do not know this. However, I notice that the Mewlon 250 has also got 3 collimation screws. I am told that only the push screws (the silver ones) do any collimation. Can I therefore transpose what I learned from the SCT collimation guide to the Mewlon 250 push screws? Do they function on the same principle? If not, is there any reliable way to predict what the screws do?

Thank you.

PS: I have tried the daytime collimation method recommended but it does not work for me...

Yihan,

I have not owned a Mewlon, so I could only guess at the effects of turning a collimation screw, just like you are guessing. My suggestion is to enlist the help of a friend to adjust the collimation screws while you look at a defocused star through the eye piece. That way you could see the effect of each adjustment as it is being made. You'll want to warn your friend to make tiny adjustments, and to make them slowly, obviously.