Telescope Reviews: More on Selecting a Good 10x50 Binocular

Last Saturday night I had the opportunity to evaluate 3 pair of 10x50 binoculars in the country. They were used primarily to hunt for M57 (see separate post on that subject). I also spent some time scanning the summer Milky Way with all of them.

The binoculars used were the Nikon Action Extreme, the Pentax PCF V, and the Orion UltraView. (I was not able to see M57 with any of them.)

As a followup to Ed Zarenski's recent report on size of good field, I will say that (for me) the Nikon Action Extreme exhibited very sharp and uniformly round tight stars out to 50% of the way from center to edge, from this point an additional 20% was fair, 15% beyond this was marginal and the remaining 15% was quite poor. The Orion UltraView were similar with the central field not being nearly as good as the Nikon and the outer 15% being not quite as bad. The Pentax PCF V were good to about 65%, fair to 80% and marginal to about 90% if not just a little more. Only the remaining 7 to 8% were poor (but not as poor as what was seen in the Nikon Extreme).

This would all equate to a good field in the Nikon of 3.25 degrees (with eyecups down one indent, I can see and measure a full 6.5 degree field), a good plus fair field of 4.55 degrees, and a good, fair and marginal field of 5.5 degrees. The Orion was similar, but with a not as sharp central field, and a somewhat better edge. The Pentax exhibited a good field of 3.25 degrees (same as Nikon), a good plus fair field of 4 degrees (less than Nikon) and a good - fair - marginal field size of 4.6 degrees which is about a degree less that the Nikon.

The whole process we follow in evaluating stars at the edge of the field is somewhat subject to debate as we are straining our eyes and looking laterally across a lot of glass. Would it not be better to shift our whole eye to near the edge of field and look at images near the edge of field head on? I know that when I just relax my eyes and look critically at the field center but with an awareness of the field edge, those stars at the edge do look better.

Enjoyment of any of these binoculars is more than just an evaluation of how stars look across the field whether we are looking at central sharpness or the integrity of stars at the field edge. For me the Orion UltraView just had eyecups that were too unstable for good use (they do have a tendency to shift). The Pentax as good as they are ergonomically and as sharp as the field is relative to other binoculars, still have a relatively narrow field. The Nikon, in spite of their falloff in performance at the field edge, do have the best performance centrally, do have the best optical feel in my hands - eyecups, ergonomics, field size (edge stars are not bad when concentrating on the field center). This all brings me to the conclusion that if I had to pick just one of these 3 it would be the Nikon Action Extreme without hesitation.

Addendum - I did get a chance to play with a pair of the Leupold Wind River Mesa in a Bass Outfitter Store in Florida earlier this week. I would say that terrestrially the edge of field is somewhat better than the Nikon Action Extreme, but not quite as good as the Pentax PCF V. As the field is just 5.5 degrees vs 6.5 in the Nikon and 5 degrees in the Pentax, the useable field is probably similar to what is seen in the Pentax with a slightly wider total field. The Leupold Wind River Mesa did look good and certainly should be considered one of the better choices joining the Nikon Action Extreme and the Pentax WP in the moderately priced 10x50 category.

Barry Simon