Spotting binoculars is a phrase people use for two different things, big mounted binoculars and a single spotting scope, and the choice between them turns on whether you value two eyes or one long tube.
What a spotting scope brings
One tube, an upright image, a zoom eyepiece and a tripod. It reaches magnifications binoculars cannot hold and is built for daylight, which makes it the right tool for reading detail at distance: plumage, rings on a bird's leg, a name on a hull. On the night sky it shows the moon and the bright planets well and goes faint poorly.
What big binoculars bring
Two eyes, a wider field and a more comfortable view for extended looking. For sweeping the Milky Way, for large clusters and for comets they are the better instrument. They do not reach high magnification and they cost more than a spotting scope of similar aperture, because there are two of everything.
For astronomy specifically
A spotting scope of 60mm to 80mm at 20x to 40x is a genuine astronomical instrument for the moon, Jupiter's moons and Saturn's rings, and it has the advantage of already being on a tripod. Its zoom eyepiece is optimised for daylight contrast, so it goes faint less well than an astronomical eyepiece of the same magnification would.
The tripod, again
A spotting scope on a photographic tripod that was fine at 20x in daylight will wobble unpleasantly at 40x on a star, because a point of light shows every vibration. If the scope is going to be used at night, the tripod deserves as much attention as the optics do.
Questions people ask about binoculars
Is a spotting scope good for astronomy?
For the moon, the bright planets and the brighter clusters, yes. For anything faint it is outclassed by a small dobsonian at a similar price.
What is the best spotting scope for astronomy?
One with the largest objective you will carry, an eyepiece that reaches 40x or more, and a tripod steady enough for a point of light.
Spotting scope or binoculars for stargazing?
Binoculars for sweeping and for comfort, a spotting scope for magnification on the moon and planets. Many observers own both.