I've been interested in getting a nice pair of large astro binoculars for some time now. I've looked at just about all the available brands at various star parties and have not found much of anything that is really constructed properly. Over the last two months I tested a number budget brands, all sourced from China, and one bino supposedly made in Japan. These are 70 and 80mm bino, 10x, 15x and 20x models. Here is what I found on almost all of them:
The 80mm binos without fail vignet internally because the prisms are too small. The entrance aperture limits the on-axis real aperture to 70mm, and the extreme off-axis to only about 45mm. The 70mm binos typically are vignetted to 60mm, and some as small as 45mm on-axis. Off-axis the illumination falls off drastically on the worst ones to about 35mm.
The next thing I found was that most of them have simple Kellner eyepieces with very poor off-axis star images, although on-axis they are not bad up to about 30 degree apparent field. The off-axis images have far more astigmatism, coma and lateral color that I can stand personally. However, what really surprised me about some of the models was the amount of spherical aberration in the front lenses. The undercorrection was so severe that only about 40mm of the full 80mm aperture was in critical focus, while the outer part of the lens formed an out-of-focus blur around each star. I have a pair of Minolta 10X45 binos with roof prisms that actually outperformed on of the 80mm binos on faintest stars visible.
lastly, I examined the coatings on the optics, including all the prism surfaces. Even the ones that were supposedly fully multi-coated had some of the internal surfaces coated with fairly high reflectivity coatings. Normally, an uncoated glass surface loses 5%, a single layer maybe 1.2%, and a multi-coated loses less than 0.5% per surface. Several of the fully multi-coated binos had prism surfaces with coatings that reflected over 5%, even though they were coated! And the eyepieces - well they had basically mediocre coatings.
About 2 weeks ago I received a pair of premium binos from a small Chinese maker which were said to be a direct copy of the 15x70 Fujinons. This sample was certainly a spitting image of that brand. The coatings are excellent all the way through, the eyepieces are nicely corrected over a fairly large field (not perfect at the edges), the spherical correction is miles better than any of the 70 and 80mm that I tested. Since I got them, the skies have been cloudy, but today it finally cleared up and I got a chance to test them on the stars.
My first test was a few minutes after sunset when the sky was still bright. The Moon was up, and the views were quite impressive with lots of crater detail even though these are only 15x. I noticed Mars nearby, and it was quite easy to see. I'm sure I could have picked it up earlier before sunset. As I panned back to the Moon, I noticed some faint stars already visible. It was the Pleiades, all members easily visible in the bright sky. This bino definitely has some excellent contrast. To say that I was pleased with these is an understatement.
Now the question. I have found what for me is an excellent bino. The company that makes them is a small outfit, and they cannot compete on price with the large makers which supply all the normal budget binos in their various configurations. These binos are basically twice the cost for the same size, but they actually work. Is there a market for something like this among cost concious amateurs?
Their specs are thus:
Total transmission over 90%. Eyepieces are special design, distortion free, flat field, sharp from center to edge. They are nitrogen filled, O-ring sealed, fog proof and waterproof. They were originally designed for extreme service for the military and can be lubed for operation from -40C to +70C. The only negative is that they are heavier than their budget bretheren, mainly because they do not use any plastic in their construction. Plus, they do not use ED or fluorite optics, something that would bump their price above $1k (it's not really needed at 15x unless you are truly picky and flush with cash). Estimated final price is around $350 if we were to import them, offer them for sale and be prepared to stand behind them warranty wise.
Is this realistic or am I blowing smoke (by the way, the owner of the company said that he doubted that amateurs would be willing to pay for what is basically a professional binocular).