Yes, HELIOMETERS is a Scrabble word!

Letter values in Scrabble US: H 4, E 1, L 1, I 1, O 1, M 3, E 1, T 1, E 1, R 1, S 1.

Is it a valid word?

HELIOMETERS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

an instrument used to measure the angular separation of two stars that are too far apart to be included in the field of view of an ordinary telescope