If it has a lens that can magnify extremely far-away objects, it's telescopic. Another way objects can be telescopic is if they are made from a series of tubes that slide inside each other.
Telescopes are the most obviously telescopic things — they magnify distant objects, like the moon, and sometimes have a series of tubes that slide out. Picture a pirate's telescopic spyglass, one type of telescope, which expands so the pirate can peer through it. If you use a camera with a telescopic lens, don’t stand too close to your subject because the lens might bonk them in the nose. Telescopic also describes something that’s only visible with a telescope, like a far-away star.