I really appreciate the wealth of knowledge and experience which you all bring to the table.
What would you consider to be "bright" objects ( other than the moon ) during night time viewing in which ED glass would make an obvious difference?
I use a pair of Nikon 12x50 SE and still see light spikes and halos on objects such as Vega. Does ED glass eliminate that?
Yes ED glass will help reduce light spikes and halos on bright objects. With refractors, there are three ways to improve the problems that not all light is focused at exactly the same place.
1. Use higher price specialty glass (ED). There are also different grades of ED glass.
2. Use a triplet (or 4 element petzval) design either with higher cost
3. Use a longer focal ratio (makes it physically longer)
For binoculars one typically wants low cost, manageable size, and good optics. You can’t get all three at the same time.
The OB 20x65 ED uses longer ratio (f-6) combined with an ED glass element to give better optics at the price of being longer than other binoculars in its aperture size.
The OB 20x80 III uses s triplet design but with inexpensive glass to keep cost down and the typical f-ratio of binoculars (perhaps f3.8 or something).
The Nikon 12x50 SE is reported to have an f-ratio of 3.7 and I’m not sure about the glass quality. I would think that if it had ED, it would have been advertised as such.
The APM 20x80 ED obviously uses ED glass (FK61) as well as the use of magnesium in the construction to keep weight down and is also waterproof to some degree. It’s f-ratio is most likely similar to other typical binoculars ( in range of 3.7 to 4).
Besides the moon, other popular bright nighttime objects are the planets, double stars, and other stars with distinct colors. There are also some DSOs that have near-by bright stars. At 20x I can see that Saturn has a ring (and not just elongated) with my OB 20x65ED (although the image is very small).