Question

what are often attached to telescopes to measure distances between celestial bodies in real - time?
binoculars
sextants
axis
magnets

Explanation:

Binoculars are for general - viewing, not for measuring celestial distances. Sextants are used for measuring angles, often in navigation and can be related to celestial measurements. Axis is a part of a telescope's structure, not for distance - measurement. Magnets have no relation to measuring distances between celestial bodies.

Answer:

sextants