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View Full Version here: : A Diagonal placed before the Focuser?

netwolf
09-05-2007, 11:24 PM
Is such a thing possible? Is anyone making such a thing. Essentially it would involve fitting the Focuser after the Diagonal.

This would help with clearance issues on fork arm telescopes.

Regards
Fahim
ballaratdragons
09-05-2007, 11:28 PM
Anything is possible Fahim.
I'm definately not an Optics knowledgable person, but I believe the focal point would make this very awkward, but maybe there is a lens you could fit into the diag to bring the focal point out the the focuser.
netwolf
09-05-2007, 11:32 PM
Ken, how is it different than putting it after the focuser. Optically I cant work out the difference it would make.
ballaratdragons
09-05-2007, 11:37 PM
Like I said Fahim, "I'm definately not an Optics knowledgable person".

But I always think 'if I change this, what will it do to the focal point?'

You may be right that it will make no difference as there are no optical elements altered.

I'll shut up now :lol:
Kal
10-05-2007, 12:25 AM
Your LX90 has the focuser built into the tube assembly Fahim! :screwy: :lol:

If you are using a secondary crayford style focuser for imaging just don't image near the zenith :thumbsup:
casstony
10-05-2007, 09:07 AM
I think this adapter from Scopestuff would screw into a sct crayford focuser then insert into the eyepiece end of a 2" diagonal (if there is enough clearance between the focuser and ota) http://www.scopestuff.com/ss_taep.htm
You might start a new trend Fahim :)
Miaplacidus
10-05-2007, 09:56 AM
Orion make a helical focusser which you can slip into the diagonal, for fine tuning when mirror shift is driving you nuts. Can't vouch for the quality, but it exists.
netwolf
10-05-2007, 05:06 PM
Kal, the idea is to use a motorized crayford style for fine focusing and remove image shift and mirror shift from the equation. Problem is this style of focuser generates clearance issues around and near zenith in alt/az mode and near the pole in polar mode.

I have looked at the helical options both from orion and borg and am yet to find a motorized option in these. If there was a motorized helical that could slot into a diagonal, this would be an ideal focuser.

Regards