Vendor for telescope mirror cells?

[JeffKoch]

Any suggestions on vendors for good, well-designed reflecting telescope mirror holding cells, in the ~ 8" diameter range? I've had enough grief from the very poorly-designed cell that holds the primary in my 7" Mak-Newtonian, and am looking to toss it and replace it with something better. Tube diameter is 8" more or less.

 

[Drakkith]

No idea. Have you tried an amateur astronomy specific forum? I'm a member of cloudynights.com myself.

 

[JeffKoch]

Ah, hadn't seen that forum - looks pretty active too, I'll dig around.

 

[DarioC]

This looks interesting.

http://www.rcopticalsystems.com/telescopes/mirror_cell.html

DC

 

[JeffKoch]

Looks nice, the multiple pad mount is what I'm looking for, my cell is just a metal backing ring that leaves the most of the mirror unsupported, with three side set-screws to keep it in place. The three screws create obvious surface distortions in a high-mag star test, and I'm sure the unsupported part adds some spherical aberration though it's hard to tell. But unfortunately those cells are for large RC mirrors.

 

[Chronos]

Another potential source is: http://www.dobstuff.com/mirrorcell.htm

 

[chemisttree]

Looks nice, the multiple pad mount is what I'm looking for, my cell is just a metal backing ring that leaves the most of the mirror unsupported, with three side set-screws to keep it in place. The three screws create obvious surface distortions in a high-mag star test, and I'm sure the unsupported part adds some spherical aberration though it's hard to tell. But unfortunately those cells are for large RC mirrors.

The 3 clips that hold your mirror might have been tightened down for shipping. Before I did anything, I'd loosen those three clips. Most have phillips head screws. The clips don't need to hold the mirror tightly, just back them off a half turn each. Overtightening those clips is a common problem (mistake) in newts.

 

[JeffKoch]

I've played with them, they're rubber-tipped allen-head set screws that keep the mirror from moving around - don't remember if they were especially tight when I received the scope 10+ years ago, but basically I can minimize the surface distortions by backing them out slightly but then the mirror moves after I collimate it. This makes it impossible to keep the scope aligned, and introduces astigmatism that is much worse than the small distortions due to the set screws. The distortions are obviously most noticeable looking at planets with high magnification, which is exactly where the scope is supposed to do it's best work - only solution I've found, short of tossing the mount and starting over, is to aperture the mirror down slightly with a cardboard annulus.

 

[chemisttree]

http://lefevre.darkhorizons.org/lxd55/clipectomy.htm" discusses those clips as well. Most mirrors don't rattle around that much when the clips are loosened. If so, you might want to dab a few blobs of silicone onto the pads underneath the primary.