Most of smaller binoculars used for astronomy deliver large exit pupil (5-7mm). In telescopes however such large exit pupils result in washed out views and bright background sky, at least from locations I typically observe. In telescopes I prefer 3-4mm exit pupil for low power wide views and was wondering if that would be the case for binoculars to.
B&H Photo was having March sale and I picked Nikon Action EX 16x50 for a good price. Last Friday I did a side by side shootout between them and my trusty Orion Worldview 10x50.
Fit and finishes look similar, although Nikon priced about double of Orion. Hopefully, it translates in better glass/coatings. In any case both are good quality mid-range binoculars. Both are waterproof, with rubber armor and long eye relief. Comfortable to use with eyeglasses, and lightweight (~2 lb) for free hand use. Orion has 6 degree and Nikon 3.5 degree
On the night of testing Ursa Major was in the right position for binocular observing. First immediate impression is darker skies in 16x50 and wider views in 10x50. While narrower, 3.5 degree of Nikon was not limiting, and overall aesthetically I preferred the views of 16x50 better.
M101 – Pinwheel gal - views were very similar, averted vision round spot.
M108 – gal – not resolved in 10x50, maybe (faintest AV spot) with 16x50.
M81 and M82 – Bode’s and Cigar gal – resolved in both binos; better details, shapes resolved in 16x50.
M109 – gal – not resolved in 10x50, small spec with AV in 16x50.
M97 – Owl Nebula – not resolved in 10x50, fuzzy star in 16x50.
C/2019 Y4 (ATLAS) – comet – faint round spot with AV in 16x50. Maybe in 10x50, but only because I found it in 16x50 first.
Overall, the exit pupil results seems to be consistent between telescopes and binoculars, and for my observing location 16x50 deliver better results than 10x50 on small to mid-size faint targets. Still, on large open clusters and nebulae, wider