This deserves its own post because I nearly forgot but it’s kinda important:
If you end up buying a reflector telescope from a garage sale, DO NOT CLEAN THE MIRRORS. Unless you can’t see your reflection in them at all, just don’t touch them. You’ll be shocked at how little the dust actually impacts your view, but these mirrors are super crazy easy to permanently mess up. If you must clean them, DO NOT use a rag, DO NOT use compressed air! Use a gentle stream of distilled water to rinse it clean. The big danger here is that you could end up dragging sharp/hard debris across the mirror and cutting some serious gouges into it. This is also true of the eyepieces. Don’t use re-usable rags to clean them. I use lintless cotton eyeglass patches to clean my pieces after fogging them up with my breath (that’s cheap and readily accessible distilled water) once I’m satisfied that they’re free of any large debris. I wipe in one direction, flip it, wipe in another direction, and dispose of it. That’s it. The eyepieces being a little dirty will mess up your view, but a dirty mirror probably won’t. Only clean it if you’re 300% convinced that you must.
Also good advice: try using the telescope at least twice before you go to the event. The moon is probably the easiest, brightest target, and it’s a good place to start with making sure your focus is close to perfect. Once you’ve got the moon, move on to a few slightly more challenging but still easy targets that you should be able to see, even in an urban area, to make sure you understand how to use the scope and put it through some actual use. A pretty easy target would be the first star out from the cup on the handle of the big dipper. Tell me what you see when you find it in the scope. Jupiter is also a pretty easy, rewarding target. The sword of Orion is another bright, easy one. Lastly, Venus is a really easy target and has a little surprise for you when you find it. But two uses is enough to get familiar with your equipment, get familiar with its use, and identify any problems before you actually get out there.