I have been using Nikon 10x50 Mariner binoculars for many years. They have provided excellent casual stargazing and provided pinpoint star images. I decided to research Astronomical Class Binoculars on the Internet with the plan to upgrade to more light gathering power. My number one criteria was optical excellence. After looking at what was offered and reading as many forums as I could find, I discovered that triplet objectives were available. The advantage of the triplet is correction of optical aberrations and a shorter focal length meaning faster optics. All optical surfaces must be coated for reduction of reflections and improved light transmission. That means dark field of view with bright pinpoint stars and other objects..
This class of Binocular needs to be mounted for a stable viewing platform. It is next to impossible to hand hold this size unit. Mounting means a rail and adjustable attachment point. You also need either a center focus with one eyepiece adjustable, or each eyepiece separately adjustable.
I decided to purchase from the Oberwerk Company based in Ohio. I found after a couple of phone calls that customer service was excellent. I ordered 20x80 D3 Binoculars. They arrived in excellent condition housed in an aluminum case. I mount them on a tripod with a Vanguard GH-200 pistol grip head. The views are spectacular. The field of view is 3.25 degrees, the exit pupil is 4mm, and the exit pupil distance is a comfortable 18mm. The triplet reduces the binocular length by about 2 inches over standard 20x80 binoculars and the weight to 7 pounds. If you have collimation problems the units have floating pads which hold the BK7 prisms and are adjustable by accessible screws. Go to the website for a full tutorial on adjustment. I would recommend this company without reservations.
Clear Sky - Rich