What is the "surface" that astronomers refer to when they measure "surface gravity" on Saturn?

Professional astronomers still refer to objects by their Messier designation, and in amateur astronomy they are among the most frequently observed deep sky objects.

Most astronomers refer to a region of small planets beyond Neptune as the "Kuiper belt", since Kuiper had suggested that such small planets or comets may have formed there.

Elaysian astronomers refer to it as the Minor Outlier.

The tables of the Shah (Zij-i Shah) originate in the sixth century, but are unfortunately lost, but many later Arabic and Persian astronomers and astrologers refer to them and also use this value.

It is the numbered stars that are usually offered for "sale" to those who want their names on them; the registrations may end up published in books that professional astronomers never refer to.

Various artworks and logos feature an astronomer peering through a 'terrascope', so Ptolemaic may here refer to Claudius Ptolemaeus.

Many astronomers refer to our Earth Moon pairing as a double planet.

But all was darkness, and astronomers refer to this as the dark age.

The astronomer was referring to the largest objects yet observed in the universe - two luminous blue arcs, hundreds of trillions of miles long, some three times the expanse of our own Milky Way.