In short, there are a few differences between spotting scopes and telescopes but both devices can be used to view space. Both options have their pros/cons! Essentially, spotting scopes are the compact version of telescopes. But, spotting scopes are ideal for viewing objects and animals on land whereas they are primarily used for looking at things in the nighttime skies. Ideally, choosing between one or the other will depend entirely on your primarily intended use.
There are two types of telescopes, one uses refracting lenses to focus light and the other uses reflecting lenses, which uses mirrors. Telescopes and spotting scopes are preoccupied on gathering the most amount of light to create the clearest images. However, while telescopes have great magnification strength, spotting scopes usually create blurry images at higher magnification. Telescopes can range upwards to 150x magnification, whereas spotting scopes usually start to become unclear and blurry at around the 60x-80x magnification range.
Spotting scopes are smaller and have fewer features than telescopes, which means that they are easier to use but cannot be adjusted as precisely as telescopes. Spotting scopes are the better option if you plan on using a scope to look at birds, wildlife, animals, or to look at plants. In general, if the main purpose of using your device is land-based than a spotting scope is desirable, but you can also view clear nighttime skies with a spotting scope, although it may not be as clear and detailed as a telescope. If you intend on using a spotting scope solely for nighttime viewing, a telescope is what you need to get because a spotting scope is better reserved for the occasional nighttime viewings. You don't need to spend extra cash on a telescope if you already have a spotting scope at home and intend on using it a few times, pus spotting scopes are generally a lot more portable and easier to carry than telescopes.
Vice versa, telescopes are not really adaptable to view things on land, and that's where spotting scopes become useful. By using a telescope for land viewings, your images can become distorted or you may even see images upside down. While you can purchase accessories to fix any issues that may arise while you're using your telescope for nighttime viewings, it's just better to purchase a spotting scope separately. And, you can find many options that are affordable!
If you love viewing the nighttime skies, a telescope will make it easy for you to do so. Since it has incredible flexibility in range, adjustments, and features, a telescope is what you would prefer to get over a spotting scope. However, since they are extremely delicate, it's better to keep your telescope in your backyard or in a stable location that doesn't require too much traveling. But, if you plan on traveling a lot, a spotting scope is what you would need since they're much more easy to carry. Both devices require you to set up on a tripod to provide a stable base.