Is a spotting scope or binoculars a better choice for astronomy? I'm interested in observing the moon and planets, and maybe some nebulae and star clusters.

I have a pair of binoculars:


Nikon OceanPro 7x50 binoculars (around \$300)
Celestron 20x80 binoculars (around $100)


I'm looking at a step up, to 100mm. Specifically, I'm trying to choose between  25x100 binoculars (either a Celestron or an Orion) and a 100mm spotting scope.

The only reason I'm considering a spotting scope is that it has a magnification of 22-66x, compared to the binoculars' 25x. But I want to check if such high magnifications really work for astronomy.

Let's say I'm observing the full moon. What's the highest usable magnification, without resulting in too dim an image?

An Amazon review says that:


  I have found that while the readability improves from 22x to about 38x
  the resolution actually decreases after that and I never use it from
  40-66x, there is no point. Maybe it would have been better to have
  optimised it for 22-40x.


If the scope is limited to 40x in daytime use, I expect it to be worse at night, even observing the full moon.

I'm considering buying the scope only for the increased magnification over the binoculars, but if I end up using the scope only at 22x, it defeats the point of buying the scope in the first place. Should I stick with the binoculars?
The main point is that it all depends on the optics quality. Nikon is a good brand, but $300  for a 50mm binocular is way too much. Remember the golden rule while buying any kind of telescope or binocular: Aperture matters, not the Magnification. In a binocular, say "7x50" models, you get 7x magnification with 50mm aperture, which restricts how far you can see. But the Celestron 80mm scope with a 20x magnification is perfectly fine. It would be advisable if you can get hold of a good tripod, get it. The beauty of the heavens is unimaginable; they shall unfurl as you explore. A 80mm scope will let you see even Dark Sky Objects like Nebulas and Distant Galaxies. 

In a nutshell, it would be best for you at this stage to grab the Celestron 20x80 scope, which is both better and less costly.