The moon and the sun make nice measuring sticks as each is very close to one-half degree in diameter. Among deep-sky objects, the Andromeda Galaxy is about 2.5 degrees long. For comets it is typically used to measure the diameter of the coma and the length of comet tails. When at its brightest, Jupiter usually displays a diameter near 0.8 arcmin. It is typically used to measure the diameter of the nuclear condensation within a comet, as well as the coma and tail of very distant comets.
Planets represent objects whose diameters are given in arcsec.
As noted under arcmin, Jupiter usually attains a diameter of 45 to 50 arcsec when closest to Earth. On the smaller side, Uranus typically reaches a diameter of 3 arcsec each year, while Neptune is normally around 2 arcsec.