Quote:
Originally Posted by Shiraz
good info there Marc - thanks for posting.
Really good idea to countersink the locking screw contact points and have now modified mine.
Am interested that you are getting good results with 3 side contact points. I found that I got minor astigmatism when I used a fairly similar setup, so now have 6 silicone dabs - still not quite perfect and am in the process of modifying it to put in 6 adjustable nylon screws on extenders to get them up to the mirror CofG - but as you say, there is not much room in there.
I guess we could just buy fully sorted scopes, but where is the fun in that? Regards ray
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Hi Ray, check your secondary as well. Astigmatism is almost always caused by the secondary offset or the surface not being flat so it may be stressed by the rubber gel that's bonding it to the plastic container. I cut mine lose, then glued some cork under the retaining clip and packed the sides with paper shims. Then I put only one dab of gel grip on the spider side of the plastic. So it's just 'hanging there' by that and the front clip.
The primary is too heavy to be siliconed I reckon. I'm not sure it would deform the figure as to create aberrations. It's still a thick chunk of glass. Although rubber gel as an incredible pull when it cures. I managed to deform the primary on my C11 by putting too much gel at some stage and that was much thicker. Since then I don't take chances with glass and tend to fit it tight but not bond it or restrict it in any way. The 3 unpainted bracket are what's holding the mirror weight. It makes contact with the glass sides. You can just rotate the mirror but it will not move sideways and it will be very hard to remove it up unless you're dead square. Like pushing a bearing on a shaft or inside a bush.
A good trick if you still have astigmatism is to rotate the primary 120 degrees, then check again. You'll find a position where it's gone. Mark it, then always remount your mirror in that position. Also mark the cell so you always match its orientation to the tube.