Is a spotting scope or binoculars a better choice for astronomy?
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.