Altair Premium Binoviewers have oversized 30mm prisms, allowing a full 28mm clear aperture for maximum performance.

This makes it more viable for use with higher-end eyepieces like the APM24mm Ultraflat with 30mm field stop as well as eyepieces with smaller field stops of around 27mm, such as the Televue 24mm Panoptic, and Explore Scientific 24mm 68°. Altair Binoviewers have a 1.25" barrel diameter nose-piece to fit into your standard telescope diagonal mirror or prism diagonal. They take up 118.5mm optical path, therefore when used with a diagonal, will usually require a Barlow lens to create enough "in-focus". This applies to most telescopes.

While Barlow lenses serve to shorten the optical path to accommodate the binoviewers, other factors such as your the amount of inwards travel of your focuser, the light path length of you diagonal and the telescope design will also influence whether or not the binoviewers will come to focus on your system. SCT's or Schmidt Cassegrains may not always require a Barlow lens, because the mirror shift focusing range is quite large.

Since binoviewers are predominantly used for solar system observing, the use of Barlow lenses is an advantage, because it allows you to maintain the more generous eye-relief of longer focal length eyepieces, making the placement of your eyes less critical relative to the rear lenses. This enables binoviewer owners to still achive medium to higher powers quite comfortably.

Some Altair refractors have a "binoviewer friendly" design with a removable extension, which serves to shorten the distance between focuser and front lens, making bino-viewing without a Barlow possible too.

Quality and performance: Altair binoviewers are are individually collimated on an optical bench for best performance. Using two eyes for viewing the moon and planets gives a much more immersive experience than a single eyepiece, with an increase in visible detail which, although unquantifiable will always be better than a single eyepiece. Almost all users of binoviewers comment they can see "half again" as much detail with binoviewers than with a single eyepiece. BK7 glass is used. BK7 gives better performance with binoviewers than the usual BK4 used in binoculars.