Question about my mirror cell

[Phil Fargaze]

I have got my 10" dob mirror out to clean and noticed that there are only three points of contact on the mirror cell. They are situated on the inner circle and consist of three cork pads. I would have thought that it would be prefferable to have the outer edges of the mirror supported as well, or is this fine for a mirror of this size?

[Moonshane]

hi Phil

a three point cell is more than adequate for a 10" mirror.

it might benefit you to move them out a little to perhaps half the radius each approx. although they are possibly not far off that now.

[Phil Fargaze]

Ok, thanks for the reassurance. I must admit, the scope seems to perform just fine so I reckon I should `leave it be`.

I did check the position and they are just a bit inside half the radius

[Moonshane]

I'm sure it will be fine. for this size of mirror three points is good. for 12"-14" probably a 6 or 9 point and for 16" and bigger an 18 point is good to about 20".