As the "clipectomy" author...
Four SN mirrors I know of have let loose in shipping. Two of them had the clipectomy, two were factory-new. In all cases, it wasn't the mirror that came loose from the mirror cell, but rather the backplate of the mirror cell that let loose from its aluminum casting. I was worried at first, but it appears that the clipectomy has little or no effect on the mirror breaking loose. Were I to ship another SN, I'd take the mirror cell off the back and pack it seperately. :)
Paul
http://lefevre.darkhorizons.org
-----Original Message-----
From: sf-bay-tac-bounces@seds.org on behalf of Jeff Crilly
Sent: Sun 5/2/2004 12:01 PM
To: The Astronomy Connection
Cc:
Subject: Re: [TAC] Meade SN-10, strong astigmatism. Help!!
When inside/outside focus is the donut squashed? Or do you see spikes?
When you say "flares" and "strong line", I'm thinking these are from the clips.
Iirc, these OTAs have mirror clips in the light path, resulting in diffraction
spikes (flares?).
The fix is to modify the clips...
http://www.astro.univie.ac.at/~exgalak/koprolin/Art/SN8/
http://www.lefevre.darkhorizons.org/lxd55/clipectomy.htm
(See bottom of page for image of flares)
Note: the above are specific to the 8 and 6 inch versions,
but I've seen some CCD images w/ the 10 that also exhibit such
issues.
Btw, regarding the clipectomy... it has been reported
that the mirrors have fallen out of the cell during shipping, so
proceed with caution. I dont have a SN, but from looking at the cell,
I would consider a full circumference baffle (kydex?) that masks the
clips. The amount of light loss will be negligable (imo) and
the contrast should improve.
----- Original Message -----
From: "Ralph Seguin" <ralph@mybrain.org>
To: "The Astronomy Connection" <sf-bay-tac@seds.org>
Sent: Sunday, May 02, 2004 1:36 PM
Subject: [TAC] Meade SN-10, strong astigmatism. Help!!
> Anybody have a Meade SN-10?
> I picked up a used one recently and managed to take it out last night
> (poor night for deep sky in my back yard in San Jose).
>
> Anyhow, I tried focussing on a star and it was almost impossible to get to
> focus and it showed strong "flares", so I racked to either side of focus
> and, sure enough, there was a strong line on each side that was orthogonal
> to the other. Astigmatism!!!
>
> Sooo.... I figure it can be in one or more of several places:
> -mirror cell pinching primary
> -corrector "cell" pinching corrector
> -secondary holder pinching secondary
> -astigmatism in the primary (boo!!!)
> -corrector plate (boo!!)
> -secondary (boo!!, but I think unlikely)
>
> The other thing that I've noticed is that the mount is obviously way
> undersized for this thing, and annoyingly loud when slewing (I don't want
> to wake the neighbors up).
>
> Anybody had experience with the SN-10 or SN series and astigmatism?
> Easy/common fixes?
>
> Thanks.
> -Ralph
>
>