Quote:
Originally Posted by alistairsam
Thanks Ray
Had a few questions
How did you use glue in your nine point cell, just small blobs around the 9 supports?
When you say crept sideways, was that due to the silicone's elasticity?
Any harm in adding silicone at the sides?
What should I look for to see effects of adhesive mounting?
Could you explain the relation between eq mounting and edge supports and why it won't work?
Thanks
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hi again
i have used a variety of adhesives - the current brew is double sided adhesive tape, since the silicone de-adhered from the GSO supports (which turned out to be thermoplastic). While it was attached, the blobs were about 1cm across and about 3mm thick - it worked well from an aberration viewpoint. the sideways creep was due to an earlier version of double sided tape that softened in the heat - silicone should not have that trouble.
I haven't tried silicone on the mirror edge, but the astigmatism from a wrongly placed hard edge mount was pretty bad.
The optical effect that I interpret as being due to adhesive mounting is a vertical gradation of the appearance of an out of focus star image - the image remains nice and round, but the pattern looks a bit different top to bottom.
All of the edge mounting techniques that I have seen are aimed at Dob mounts, where gravity has a fixed orientation wrt the OTA. on an EQ mount, the direction of "down" varies with where the scope is looking, so it is not possible, for example, to put supports at the recommended plus and minus 45 degrees from the bottom of the mirror - as soon as you move to another part of the sky you have to rotate the OTA to get the supports back in the right orientation. And the last thing you want is a hard edge support in the wrong place.
regards ray