Telescope Reviews: Meade 7" Maksutov Collimation

I think this is the purpose of the mirror lock. It's for squaring the primary with the optical train after it has been focused. In fact, I've read were other people recommend setting the mirror lock so that it slightly drags, so that the primary will remain reasonably square with the optical axis while it's being focused, and then locked afterwards in order ensure that it's squared up properly. Does your's have the mirror lock?

I also read about another person who had used the push-pull screws to try to fix a slight miscollimation, and in doing so actually made it worse! They weren't able to undo what they did because the misalignment they were originally trying to fix made it impossible for them to accurately undo their adjustment. Instead of making it better by adjusting the push-pull screws, they actually made it worse by adding another alignment error to the already existing error!

This is why I posed the question, as I have a hunch that some people may be incorrectly intuiting the purpose of those screws as having the same affect as the adjustment screws on the secondary of a typical SCT or newt. From what I've been reading it seems that, while they may be adjusting the secondary's tilt, more importantly they're actually allowing you to adjust the meniscus in parallel with adjustments made to the primary as it's collimated. I don't completely understand it, but I believe that those screws may have more to do with maintaining an important relationship between the meniscus and the primary, and less to do with adjusting the tilt of the secondary, though that's also happening. The Meade has a spherical secondary, and an aspherical primary.

From what little I think I know about this, while most other Gregory/Maksutovs don't have push-pull meniscus cells, their meniscus' must still be shimmed in order to maintain that spatial relationship with the primary. In doing so, the secondary alignment pretty much takes care of itself. The crux of the matter being that the relationship of the meniscus to the primary is the more critical dimension, which cannot be correctly set by merely attempting to align the secondary spot. I think this may be why out-of-focus star images on many factory collimated Gregory/Maks appear to show them to be out of collimation, when in fact they are perfectly collimated at the focal plane.

That being said, I'm certainly no expert in any of this which is why I'm tossing it out for discussion with the hope that someone who does this a lot, like Dr. Clay, might also chime in on it.

Edited by mayidunk (12/05/12 05:29 AM)