Is Celestron cheating us with their binoculars ?

[skysurfer]

The Skymaster 15x70 has actually 65mm aperture, revealed by me (and others) with the flashlight test: focus to infinity, put a ruler a few cm in front of one of the objectives and hold a flashlight a few cm behind the eyepiece. This will reveal the actual objective diameter.
The Skymaster turns out to be only 65mm, but the price of $130 is also not a price for which you can expect much.

But the more 'premium' Echelon 16x70 of $1000 turns out to have the same issue: objectives stopped down to 65mm and for such a price it is a cheat :mad2:

https://www.cloudynights.com/topic/581619-celestron-echelon-20x70-vs-minox-bd-15x58-ed-br-mini-reviewcomparison/

[bigjoe]

Theses things happen with quite a few brands..Even scopes... the 127mm Mak primary mirror is about 120mm actually, but still performs brilliantly with Schott glass...what can you do though.

bigjoe.

[Slawomir]

Although 65mm is only a few% less than 70mm in diameter, but in terms of surface area and thus light gathering the difference is about 14% less, which is significant.

[Atmos]

If the front lens on the Mak works as a lens you don't need a 127mm primary mirror as long as the front aperture is 127mm diameter.

[bigjoe]

Indeed corrector is 127mm..

Those light rays diverge past the secondary baffle in these due to that thick meniscus , and dont cause the obstruction you would think in these Maksutovs.

Usually the primary should be at least the size of Corrector ..but this is a moot point, as optics in these are really superb.
bigjoe