What mirror cell to use?

Hello all....

I have been using a 12 1/2" Orion Deep Space Explorer (Discovery) for about 7 years now.....cannot afford to go larger as i would like to.....so I thought that I would try to modify my scope by ventilating it (it has 3 holes about 2" in dia.) and at the same time make it a little lighter.

I can purchase a mirror cell from UO for less than $50 or I could get one from K. Novak for around $255 and several others for prices in between.

Would you advise against the UO cell...if so...what would you suggest?

Thanks in advance...Roger in Tampa, Fl.

Pass on the UO cell.
There is a reason that these cost so much less than other aluminum cells. Yes, they are open, light weight, and collimate quickly. The catch is mirror support, or rather lack of.

Their 12.5" cell that I had was a only 3 point. Their 13" is a nine point, but it's three groups of three in radial lines like spokes. This poor support yields astigmatism. Your images will certainly suffer, in my experience. Any additional adaption to the cell in the way of mounting bolts, stiffer springs etc, will nibble away at the cost savings.

Their cells are in fact very robust. And affordable. They are a good cell for smaller mirrors. But, they are poorly designed for a scope this size, IME.

I have a Discovery 12.5 incher that is of the same vintage as you Orion scope though it is a 12.5 incher. It had a particle board cell which I replaced with a UO cell which used the "9 point" flotation, but it was, as mentioned, 3 rows of 3.

The scope lost about 9 lbs, a very good thing as the OTA was now down around 48lbs. This required moving the trunions and replacing the side boards, over all a great thing for the scope.

Then I bought a Novak cell off astromart for about $70 and replaced the UO cell. The Novak cell is clearly slicker, a nice 9 point floation and solid aluminum.

There were a couple of hitches, my mirror is a 1.5 inch mirror, the Novak cell requires a minimum of a 2 inch mirror. It also weighs more.

Does it make any difference? I am not sure, I don't really think so. If I were in your shoes, I would just go with the UO cell and see how it works, the price is right.

I also suggest using the computer code (freeware and I can't think of the name) that allows you to model the deformation of the mirror as a function of how it is mounted.

Best wishes

jon