Suppressing mirror flop in 10" GEM mounted Newt
As part of an ongoing project to minimize cone error in a GEM mount, for my 10" Newt I have things isolated down to mirror flop. You follow the flop rotating the scope from east to west RA and a Zhumell laser collimator. Does anyone have any recommendations on how to temporarily but safely suppress mirror flop in a 10" Orion Newt? I'm assume that the cell simply needs to be removed and the clasps holding the mirror in place tightened. On the otherhand, I understand that the free-flop movement is there to prevent stresses from building up in the mirror. - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net
Kurt, does your cell have both face clips and centration adjustment? Or just the face clips? Both face restraint and centration adjusters must be addressed. A slight bit of mirror slop is desirable in a visual telescope, but for imaging it can cause problems, as you are aware. There are materials and techniques available now that will allow you to restrain the mirror more firmly without introducing stress. I seem to recall mentioning primary mirror movement at the start of this thread. On 8/13/07, Kurt Fisher <fisherka@csolutions.net> wrote:
As part of an ongoing project to minimize cone error in a GEM mount, for my 10" Newt I have things isolated down to mirror flop. You follow the flop rotating the scope from east to west RA and a Zhumell laser collimator. Does anyone have any recommendations on how to temporarily but safely suppress mirror flop in a 10" Orion Newt? I'm assume that the cell simply needs to be removed and the clasps holding the mirror in place tightened. On the otherhand, I understand that the free-flop movement is there to prevent stresses from building up in the mirror. - Kurt
Quoting Chuck Hards <chuck.hards@gmail.com>: Silicone adhesive comes to mind.
There are materials and techniques available now that will allow you to restrain the mirror more firmly without introducing stress.
I seem to recall mentioning primary mirror movement at the start of this thread.
On 8/13/07, Kurt Fisher <fisherka@csolutions.net> wrote:
As part of an ongoing project to minimize cone error in a GEM mount, for my 10" Newt I have things isolated down to mirror flop. You follow the flop rotating the scope from east to west RA and a Zhumell laser collimator. Does anyone have any recommendations on how to temporarily but safely suppress mirror flop in a 10" Orion Newt? I'm assume that the cell simply needs to be removed and the clasps holding the mirror in place tightened. On the otherhand, I understand that the free-flop movement is there to prevent stresses from building up in the mirror. - Kurt
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Yes, that is one of the partial options, but it has a problem- it yields. It needs help for astrometric applications. It's really just a substitute for face clips on small and medium sized mirrors. Unyielding lateral support is still required, such as hard nylon. On 8/13/07, diveboss@xmission.com <diveboss@xmission.com> wrote:
Quoting Chuck Hards <chuck.hards@gmail.com>:
Silicone adhesive comes to mind.
How are you attaching that? Quoting Chuck Hards <chuck.hards@gmail.com>:
Yes, that is one of the partial options, but it has a problem- it yields. It needs help for astrometric applications. It's really just a substitute for face clips on small and medium sized mirrors. Unyielding lateral support is still required, such as hard nylon.
On 8/13/07, diveboss@xmission.com <diveboss@xmission.com> wrote:
Quoting Chuck Hards <chuck.hards@gmail.com>:
Silicone adhesive comes to mind.
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The hard plastic. Quoting Chuck Hards <chuck.hards@gmail.com>:
Not sure I understand your question, Guy. Attaching what?
On 8/13/07, diveboss@xmission.com <diveboss@xmission.com> wrote:
How are you attaching that?
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OK, I see. The Nylon is used in the form of hardware. 3 plastic screws used for centration adjustment, near the rear face of the mirror so no distortions are introduced on the optical face. They are turned until they just touch the edge. The mirror cools during the night, so it contracts slightly. No strain is introduced from the clips because the pressure isn't increasing. Pyrex contracts very little; in practice a gap never really opens-up. Face clips are not needed if the telescope never tilts past horizontal- as some large Dob owners can attest-to, but it's typically not possible with a portable, close-tubed Newtonian. What Kurt is trying to combat is the lateral motion, not fore-and-aft mirror shifting. I should take some photos of my home-made 10" floatation cell. 9-point support, completely adjustable centration, fan cooled with internal batteries. On 8/13/07, diveboss@xmission.com <diveboss@xmission.com> wrote:
The hard plastic.
Quoting Chuck Hards <chuck.hards@gmail.com>:
Not sure I understand your question, Guy. Attaching what?
On 8/13/07, diveboss@xmission.com <diveboss@xmission.com> wrote:
How are you attaching that?
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participants (3)
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Chuck Hards -
diveboss＠xmission.com -
Kurt Fisher