UO Mirror Cells

I have an 8" f6 Discovery Dob. The Primary is off center in the tube by about 3/8ths of an inch. The Discovery cell doesn't provide any means of precisely centering the mirror in the tube.

The UO mirror cell appears to provide centering adjustments by means of its mounting screws. Can anyone confirm whether this is true? Also, the cell retains the mirror with rubberized (?) metal clips. Will the clips cause distortion of the image created by the mirror? Would like to hear from anyone using these cells.

The mirror is attached to its backing plate in the current cell with adhesive of some type; possibly RTV. What's the best way of seperating the mirror from its plate?

This scope has never collimated the way it should and performs rather poorly on close double stars. I'm hoping to correct these problems by centering the mirror in the tube and re-collimating. Is this reasonable, or should I look elsewhere?

Thanks.
Bob

Hey Bob,
I have had a UO cell pass through my hands and had a good look at it--but I've always only used my home-made cells. But I'll try and answer your questions....

"The UO mirror cell appears to provide centering adjustments by means of its mounting screws. Can anyone confirm whether this is true?"

YES.

"Also, the cell retains the mirror with rubberized (?) metal clips. Will the clips cause distortion of the image created by the mirror?"

NO, if you're careful. The clip height is adjustable--I would set it just above the mirror surface, so as to catch the mirror if for some reason you tipped the scope below horizontal. Or you could follow Royce's advice and just eliminate the clips (they were removable on the model I had), and install a stop on the rocker box to avoid tilting the scope that far. Now you could bring the clips in contact with the mirror, and most likely any contraction in the metal would be absorbed by the rubber, but I don't think that's necessary.

"The mirror is attached to its backing plate in the current cell with adhesive of some type; possibly RTV. What's the best way of seperating the mirror from its plate? "


REMOVE the cell with mirror. place a clean cotton cloth on a table and put the mirror face down on top of it. Cut the atv with a thin gauge wire or long knife.

"This scope has never collimated the way it should and performs rather poorly on close double stars. I'm hoping to correct these problems by centering the mirror in the tube and re-collimating. Is this reasonable, or should I look elsewhere?"

You cannot have any idea of the quality of the optic until you have collimated it properly, so I would try something like the above first.

best wishes,
george