Binocular FL?

A couple of days ago at 'that auction site' a pair of 10 inch aperture aerial lenses sold for more than $2600. Silly me, I thought I'd be able to snatch them up for less than $500.

Anyway, based on the description, these apparently were @F3, which would seem a bit short for a pair of giant giant binoculars (which was my grandiose plan...). Are there such? Or would they have required Barlows to make up the difference?

Jess Tauber

I would think there would be exit pupil problems. At lower power the exit pupil is huge. 30X provides an 8mm EP. To get a 5mm EP requires 50X which can be obtained with a 15mm eyepiece. Any brightness at all in a target will require smaller exit pupils for visual use or there will be a waste of aperature. So why not just use the smaller aperature to start with and save the expense of big glass and big mounts?

The question remains as to the optical quality of the lenses when viewing at higher powers with reasonable exit pupils. The lens was probably designed for large wide flat field imaging and as such, on axis images were likely compromised to improve the edge of the field and flatten the image plane. At 50X viewing, star images may begin to soften noticeably.

I could be wrong but I doubt these lenses would make a sucessful bino.

dan