Re: ATM astigamatism

["Frédéric Géa" <geaf@unionfinancieredefrance.fr>]

I forget, seems to be better when the sling is around less than 50 % of the
mirror perimeter.


Frédéric Géa
http://www.astrosurf.com/altaz
-----Message d'origine-----
De : Jan van Gastel <jhm.vangastel@wanadoo.nl>
À : 'ATM' <atm@shore.net>
Date : mardi 6 mars 2001 13:27
Objet : ATM astigamatism


>
>I cut one of the three silicone pads which attach the secondary to its
mount
>totally and the other two partly. But: the astigmatism is still there, and
>still in the direction the telescope is pointing.  So I think it is not in
>the mounting of the secondary. It could be the secondary AstroSystems
>Premium) itself of course. I don't know if this is plausible. BTW: it is
not
>easy to cut the (3 mm thickness) silicone blobs. I tried with a hacksaw
>blade, but it binded before I was halfway through the blob. With difficulty
>I succeeded with a sharp knife.
>
>I think I will cut all 18 blobs with which the primary is mounted this
>weekend and make a sling. My (Krige/Berry type) tailgate is prepared for a
>sling, so this must be no problem. I'll make the sling from a safety belt
of
>an old car. Kriege and Berry advise to use furniture pads as support point
>for the primary. I also read soewhere that teflon can be used, but this
>cannot be glued. Which kind of stuff can be recommended?
>
>Another question: when using a sling, how can be decided whether it is the
>primary or secondary mirror that must be collimated or if the sling must be
>adjusted?
>
>Jan
>http://www.geocities.com/janvangastel/
>
>