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Old 29-11-2010, 08:00 PM
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Jason D (Jason)
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Jason D is offline
 
Join Date: Aug 2009
Location: California USA
Posts: 117
Quote:
Originally Posted by mswhin63 View Post
With those twist clamps for lenses, the focuser adjustment is not much of an issue, I will be buying one of these later and will check.

Focuser axial alignment is about eliminating tilt between the primary mirror and eyepiece focal planes. This can only be accomplished by adjusting the secondary mirror. I have described the two typical methods used to complete this alignment in my previous post. This alignment is completely missing from the video. The "Precision Centering Adapter" shown in the video has little to do with this alignment.

Quote:
There are a couple of things I would do a little differently, for primary adjustment placing in both horizontal (near enough to) and 60deg is a good idea for both. Only recently I was checking mine and picked up a set-up error with my scope checking both,

Aligning the primary mirror with the OTA in horizontal position can be problematic since primary collimation might shift substantially after the OTA is raised.

Quote:
but I think it was also placed horizontal to allow better youtube instruction.

The presenter could have said something to this extent.

Quote:
Although mostly not for primary adjustment it is good practice not to tilt a newtonian above 45deg as it is possible for things to fall or be flicked in and potentially damage the mirror. I think that was mentioned in the video although I do remember this being a concern before watching the video.

The primary mirror adjustment takes place at the rear end of the scope. Dropping objects on the primary mirror should not be a concern. For the secondary mirror adjustment, Bob's knobs could be installed to reduce the likelihood of dropping objects.

Quote:
I'd be interested in knowing why you would put it at 60 deg and not lower?

The 60 degrees is only a guideline -- not a rule. It is recommended to collimate around halfway of the user's observing ALT range. Typically, that would be between 40 and 80 degrees. 60 degrees happened to be the halfway point. Again, this is only a guideline.

Jason

Last edited by Jason D; 30-11-2010 at 08:32 AM.
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