Hunter's and nature observer's. They prefer the 18x56 Vortex Razor UHD over a spotting telescope because it is more comfortable to use with two eyes and has a bigger FOV. I plan to use mine for wolf spotting in Yellowstone National Park. Many will use it on a tripod but some will use it hand held. I have used mine on the night sky also and it is a great binocular for that especially on the moon. The big 56mm aperture and 18x magnification is almost like using a small apo telescope. You can see a lot more detail and pick up many more faint fuzzies with a 56mm versus a 50mm. Roger Vine says they may be the best hand-held astro binocular he has ever used.
That big Nikon 18x70 is great for astronomy. I had a Nikon Monarch 5 20x56 and it surprised me how good it was for astronomy and observing for a $500.00 binocular. Of course it was not as good as the UHD 18x56. The UHD 8x42 will surprise you how good it is. This morning I was trying all three of my 8x42's the UHD, the FL and the EDG and they are really close. They are all really good. But if I had to rank them it would probably be UHD followed by FL and then EDG optically. The AK prism makes the UHD and the FL noticeably brighter than the EDG and the UHD and the FL are just a little sharper on-axis. I really think an AK prism binocular has better contrast also. The UHD has sharper edges than the FL and a bigger FOV and it just seems to have a little better contrast and more pop than the FL. The blacks for example are blacker in the UHD than the FL. The UHD is REALLY sharp on-axis. I have always felt the FL is the sharpest binocular on-axis but the UHD might be a little sharper or at least it seems that way because of the better contrast. All three of them are superb binoculars. The handling and comfort of the EDG and the focuser are hard to match. It would be very hard to decide which one to keep if you could only keep one of the three.
I've liked Roger's reviews very much, but also find all this a contradiction with the glowing "Alpha" verdict. (Then again, various Zeiss models had obvious off-axis astigmatism for a long time...)
I have no problem with drifting diopters in either my 8x42 or 18x56 Razor UHD's. In fact I don't see how it is physically possible for a diopter that locks on the ocular to move from a focuser that is not even attached to it in anyway. It doesn't seem feasible. There can always be sample variation even in alpha's but I find it surprising. My Razor UHD 8x42's have some of the best CA correction I have seen but there is some edge CA on the UHD 18x56 which I would say is due in large part to the high magnification. Roger commented the SLC 15x56 controlled CA better than the UHD 18x56 but there is a BIG difference in magnification when you go from a SLC 15x56 to a UHD 18x56.
