Star diagonals : 2" vs 1.25" on C100ED & focusser lubricant

[Totnesdave]

Hi guys & gals

A question on star diagonals, and focus tubes etc

I thought my Celestron C100-ED only took 1.25 inch eyepieces, however I didn't realise that it is actually engineered for 2 inch eyepieces with a 1.25 inch adaptor already in place

So….. if I upgrade my star diagonal at some future point, would it be better to :

(a) get a 1.25 inch version and mount eyepieces in it as I already do with the stock Celestron one or ...

( get a 2 inch version, fitting it directly to the focuser tube and placing the existing 2/1.25 adaptor into the star diagonal.

What are the advantages/disadvantages…can anyone enlighten me please ?

If I do upgrade at some point, it may well be one of the William Optics dielectric diagonals, or something similar.

I also read that the stock focusser improves when the sticky lubricant (pine tar?) is cleaned off and is replaced by other forms of lubricant (silicon/graphite?) .. can anyone shed further light on this (best substances etc) ?

Many thanks

Dave

[michael.h.f.wilkinson]

2" diagonals are worth it. I have a WO dielectric and love it. Because the centre of dielectric diagonals are better corrected than the edges, 1.25" diagonals are not quite as good even for 1.25" EPs as 2" diagonals are. The only two disadvantages are weight and price, but neither need prohibitive. Ever sine I got my 2", I never used the 1.25" again (stock Celestron one).

Cheers

Michael

[NGC 1502]

Hi, the advantage of a 2" diagonal is it allows you to use low power 2" eyepieces for a very wide field of view, great for objects like the Pleiades, Ed.