Anybody know what a "mirror blanking plate" for a C-8N looks like ??

[Craney]

Evening all,

I answered a small add from a chap who wanted a second hand Celestron C-8N  ( that's the Newtonian F5, not an SCT ).

No problems as I have one which doesn't get much use.   In his ad  he asks for the  " mirror blanking plate" which came along with it when new.  

Since I bought it second hand myself I was not sure if I had it to hand or had put it away in a box.    I tried to google what one looks like and nothing came back,

I have looked in the C-8N manual and there is no mention of it, or use of it........    does this thing exist ??

Anybody out there  shed any light on the matter   ??

 

Rgds,  Sean.

[CraigT82]

I think it's the steel plate on the back end of the tube that covers the collimation screws and generally closes off the tube, usually found on smaller newts. No idea if the C8N would have had one originally, sorry. 

[John]

F/5 newtonians made by Synta (such as the Celestron C8N and the Skywatcher F/5 newtonians) used to have these plates over the rear of the primary mirror cell held in place by 3 small screws. They are not really necessary - I used to remove mine a put it away and forget about it when I had these scopes. The plate got in the way of the collimation adjustment screws and, in my view, slowed down cooling a bit. For some reason Synta never included them in the 150mm F/8, 200mm F/6 and larger dobsonian mounted newtonians. Synta also make Skywatcher scopes by the way.

 

 

Edited July 2, 2021 by John

[Craney]

18 hours ago, CraigT82 said:

I think it's the steel plate on the back end of the tube that covers the collimation screws and generally closes off the tube, usually found on smaller newts. No idea if the C8N would have had one originally, sorry. 

Thanks,  nearly all the scopes I have bought second hand and the original owners must have discarded the plates as a faff.  I was at a bit of a loss to understand the function.

 

16 hours ago, John said:

The plate got in the way of the collimation adjustment screws and, in my view, slowed down cooling a bit.

Indeed.  I'm always back and forth between the end of the scope when collimating.  I'm sure this plate would have been float tested very soon or used as a plant stand.

My potential buyer suggested it might be a protection feature if you regularly stand the OTA on it's end, for example on a rough surface.  

Anyway thanks for the info.  I will have a root around my box of  'strange and of unknown origin'  accessories to see if anything looks likely in there.

 

Sean.

Edited July 3, 2021 by Craney