Queen and huntress, chaste and fair,
Now the sun is laid to sleep,
Seated in thy silver chair,
State in wonted manner keep:
        Hesperus entreats thy light,
        Goddess, excellently bright.
 

Earth, let not an envious shade
Dare itself to interpose;
Cynthia's shining orb was made
Heaven to clear when day did close:
        Bless us then with wishèd sight,
        Goddess, excellently bright.
 

Lay thy bow of pearl apart,
And thy crystal-shining quiver;
Give unto the flying hart
Space to breathe, how short soever;
        Thou that mak'st a day of night,
        Goddess, excellently bright.

He is addressing the Moon, whose names were:

• Diana or Cynthia in Latin;
• Artemis in Greek.

Diana was a huntress. She was also a " Perpetual Virgin " - 1 of only 3 gods or goddesses immune to love (Athena & Hestia were the other 2).

Diana thus became an emblem of Queen Elizabeth, whose public persona was that she was a virgin.  If she married, she'd have to share the power, so retaining her virginity and not marrying allowed her to retain her power.)

Hesperus is the "western star,"  which we call Venus.  In its evening star position, it rises at sunset, shortly before the full moon would rise.  Thus it "entreats thy light," that is, it calls it to come up & shine.

Earth (people) should not interfere with the moon (Elizabeth).
"shade . . . interpose" = an eclipse of the moon.

He asks Elizabeth NOT to hunt him.  Elizabeth was the source of advancement at the court, but if you got her angry, she could also kill you.  In the myth of Actaeon, Actaeon was out hunting with his dogs when he stumbled on Diana and her nymphs bathing.  As punishment, Diana turned him into a deer & his dogs, not recognizing their master, tore him apart.

This poem was written in 1600.  The Earl of Essex was beheaded in 1601, showing Elizabeth's power of life & death over the men of her court.