How much aperture does it take?

Seeing Mars through a telescope

A small orange dot for most of its cycle. Near opposition, every two years and two months, a 150 mm shows a polar cap and dark markings.

Through three telescopes, under a suburban sky

Each circle is the true field of a 10 mm eyepiece. Same target, same sky; only the aperture changes.

70 mm · 49×

Detectable

130 mm · 91×

Recognisable

250 mm · 175×

Detailed

Mars does not care about light pollution: it is bright, and the air, not the sky glow, sets the limit.

Level	Milky Way blazing	Milky Way, barely	No Milky Way
Detectable	20 mm	20 mm	20 mm
Recognisable	100 mm	100 mm	100 mm
Detailed	200 mm	200 mm	200 mm

Away from opposition Mars is genuinely disappointing in any instrument. This is a timing problem, not an aperture problem.

Only worth the effort within a few months of opposition.