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Mirror cell question

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#1 Scott Hamilton

Scott Hamilton

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Posted 20 January 2004 - 09:40 AM

I've recently purchased the GSO 8" Dobsonian reflector and one
of its characteristics has got me concerned. The newer models
have got a different mirror cell, the new one being completly
open to the extent that the mirror is only supported at the
very edge.

This runs counter to all of the advice I have seen in ATM circles,
to include the PLOP mirror cell calculation program, in which the
ideal support points should lie at a point 40% of the distance from
the center to the edge. For an 8" mirror there should be three,
equally spaced 60 degrees apart.

I would be interested in what you all think. I am not experienced
enough to be able to factor out the effects of this at the
eyepiece although the difference according to PLOP should be
substantial.

Scott

#2 rboe

rboe

    ISS

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Posted 21 January 2004 - 06:52 PM

Flexure will depend on the thickness of the mirror and for an eight inch mirror you may be OK. Live with it for a while, see how it star tests and consider your options if a change seems in order (or return it if it really bothers you). Mirror cells are "cheap" so you could easily replace it.

But I suspect that an eight mirror, being small, is pretty stiff an immune to flexure to a degree you are concerned about.




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