locking screws and collimation screws. Which ones are which?

[Craig.a.c (Craig)]

When I got my GSO dob I adjusted the collimation of the secondary mirror, easy enough. For the primary mirror I'm not sure which screws are which for locking the mirror and the collimation ones. Does any one have a diagram that shows what they are?

Cheers - Craig.

[davewaldo]

Hi Craig,

Usually the larger screws are for adjustment and the smaller ones to lock it off.

The screws work on a push / pull system. The locking screws push on the back of the mirror cell to lock it in place. There are springs in there too which push the cell to help when adjusting.

Its the pulling screws which you adjust. Its easy to tell which is which. The locking screws move up and down when you screw them in and out. The adjusting screws always sit flat on the back of the cell. Also the locking screws will feel quite loose until they actually lock against the cell. The adjusting screws always feel like they are under tension from the springs.

Does this make sense?

So the procedure would be to loosen the locking screws. Make your adjustments with the other screws then lock it all back up.

Hope this helps

Cheers!

[iceman (Mike)]

Dave is right.

Collimation screws have springs, locking screws don't.

[Craig.a.c (Craig)]

Thanks for the info Dave, much appreciated.

[rayman888 (Ray)]

First post on this forum. Infact first post in any astronomy forum! So be nice.

On my just purchased Celestron Powerseeker 127EQ there're 3 pairs of screws on the back plate. All look the same and one of each pair is screwed right down to the back plate. In fact looking inside the telescope, these screws appear to secure the back plate to the tube. Wish Celestron would use a different set of screw, eg fingers useable, instead of the same philips head screws. Couldn't have cost much more, and more helpful to a novice like me! Or place arrow stickers next to the ones I can mess with. And is it me or does the manual appear a bit vague to other owners? Is it me or the telescope when the terrestial images double focus and then out of focus again, say an image less than 500m away? Any advice will really help. Thanks.