Mirror Cell to suit a 17.8" Coulter Mirror

[gaa_ian (Ian)]

GAA have a 17.8 inch Truss tube dob we have had for a few years.
We need to improve the mount for the mirror cell to make it more robust.
Can anyone make a recomendation for a mirror cell that will accommadate this size mirror.
It is currently sitting on a pivot pin and see-saw arrangement of 3 individual cells (very fragile)
We need a robust mirror cell to mount the mirror on.
Any suggestions where we can get one ?
Regards
Ian
President Gove Amateur Astronomers (NT)

[mental4astro (Alexander)]

Hi Ian,

Get one? Why not make one! Mirror cells are not overly difficult things to construct. And you can control the entire process, design, engineering, materials, etc, especially if all you intend to do is replace the existing cell, and want the new one to fit into the existing OTA. It will also be a much cheaper exercise than sourcing a commercially made one.

There are many internet sites that offer the design parameters. I'll try to dig up a couple of links for you.

The other thing I'd suggest is that you get your hands on a copy of "The dobsonian telescope: a practical manual for large apeture telescopes" by Kriege & Berry. You can get a new copy from Bintel. This book contains all the info you need to construct a magnificent cell.

Here is a first link to get you started. It is a good reasource for ATMers:

http://stellafane.org/misc/links.html

Mental.

[asimov (John)]

I agree with Mental - I've made at least 4 cells over the years. Very easy to do. You'll save yourself some bucks in the process, obviously.

[gaa_ian (Ian)]

Thanks John and Alexander
I have already had a look at some of those links and have put it to our club equipment curator, to take up the challenge !

[scopemankit (Chris)]

I've just finished a scope with an old Coulter 17.75 and it works well. Here is a pic of the cell and the scope. The white disks on the 18 support pads are corrugated plastic. The mirror rests on these and is supported by a sling. Retaining clips (just above the mirror edges) prevent the mirror tipping forward if the tube is tilted too much.

[mental4astro (Alexander)]

WOW, Chris! Mate, most impressive. This is the sort of thing that inspires me to undertake another project, .

How long did the planning & building take? All on your own, or did others help with particular skills?

Alex.

[scopemankit (Chris)]

Six months - on & off

[gaa_ian (Ian)]

Thanks Chris
That will be very helpful.
Nice looking scope, looks a good deal lighter than the one we have.
The mirror box is a 2 person lift !

[erick (Eric)]

Do you want to buy some pre-built parts?

The Glatter Cable sling has got a number of fans. See the thread named "Glatter Cable sling" in the Reflectors forum of Cloudy Nights.