The Binocular Sky


Binocular Sky Ratings

Scoring equipment is fraught with difficulties and inconsistencies; I am fully aware that others may disagree with the scoring system I use: the reason for publishing this detailed description is that it enables you to at least compare items I have reviewed and, if you wish, "transpose" it to a scoring system that you like.

Sharpness of Image This is based on the ability to split a double star at the centre of the FoV when the binocular is mounted. The star used will normally be chosen so that:

Size of usable field This is the size of the field within which the image of the double star above does not begin to break down:
(% of field * True FoV * Magnification / 600)
(Yes, I do realise that based on this some top-end binoculars like the Swarovision EL 10x50 would have a score of 11/10 :-) )

Colour correction This is based on perceived colour from the lunar limb between 1st and last quarters.

Control of stray light This is based on spurious reflections from the Moon between 1st and last quarters.

Eye relief


Focus mechanism

Right Eyepiece adjustment 'Properly set' means that it is at its zero/central position when used with properly corrected vision.

Eye cups



Weight and balance (Applies to binoculars up to 10x50 only) This is obviously somewhat subjective and is comparative to other binoculars of the same or similar size.



Objective caps

Eyepiece Caps/Rainguard

Value for Money My subjective opinion.