Making Mirror Cells

[Nick1 (Nick)]

I am planning to build a lightweight 14" Newtonian to be mounted on an equatorial mount (yes I know, bucking the trend to dobs).

When it comes to the mirror cell there seems to be three options:
(1) Buy a manufactured aluminium mirror cell. These seem to be few and far between above 12.5". An example would be the one from Orion Optics UK. These are not cheap and are heavier than I expected.
(2) Get one machined locally. BIRD's example for his 16" would be an example.
(3) Possibly - make one from quality plywood.

I am interested to know if anyone has experience with making wooden mirror cells? There are designs on the web for smaller scopes, eg 8" and 10", but I haven't seen any for larger mirrors.

Two more questions:
(1) 14" seems to be the point where some recommend 9 point flotation and others move up to 18 point flotation. Any views out there on this?
(2) Is there somewhere I could buy the triangular support pads for the cell, or are these a DIY proposition.

Regards
Nick Potter

[SkyViking (Rolf)]

Hi Nick,

If you want a lightweight Newtonian then I'd recommend a conical mirror mounted with a single bolt though a backplate. A tiltable piece of ply is all the mirror cell you'd need in that case.
This is what I'm currently building, for a Royce 12.5" mirror:
http://www.rolfolsenastrophotography...4423&k=vcnLTsG

Cheers,
Rolf

[Nick1 (Nick)]

Thanks Rolf. Good food for thought.

Nick

[gbeal]

And I'll throw in a couple of other ideas.
For my 10" f5 newt with a decent thickness I used to have a University Optics aluminum cell. Worked a treat, heavy as hell, but worked.
Sold it, and built two sorts. One from foam core, which I wrapped with C/F and gel. Another from two slabs of 6mm stainless steel. Oh, and since the pictures were taken I have gone to better knobs, better looking anyway.
On both occasions I simply silicon the glass to the cell.
Both work wonderfully.
Gary

[Nick1 (Nick)]

Thanks Gary. Could you point me to any info on the web on how to wrap carbon fibre around a core like you have done.

Nick

[gbeal]

No Nick, I can't. I guess there will be some out there, but in my case "I just did it".
I cut the foam core into the shape(s) I wanted, there are two sections obviously. I glued the collimation bolts into one section, and the tube attachment threads into the other.
Then I cut as carefully as I could some C/F weave material. Looking at a single triangular shape I cut two triangular pieces of weave, one for the front, one for the back, obviously, and then strips that formed the "sides".
Then it was just a matter of brushing on some resin and putting the weave in the correct places, and then more resin on the outer side.
It really was that simple, but at the time it didn't feel like that, LOL.
Have a go, apart from material wastage there is little else to go wrong.
Gary

[Nick1 (Nick)]

Thanks Gary. I think I'll have a go.

Nick