Get your scary costume ready for great costume contests this weekend. (David S. Holloway/GETTY IMAGES)

Officially, Halloween isn’t until Monday, but two of the area’s best costume contests are this weekend. DC 101’s Eliot in the Morning takes over Clarendon Ballroom for a Monster Bash of rock covers by Junkfood and music spun by DJs. Up for grabs in the costume contest is a $3,000 prize.

Over at District, Hot 99.5 will be hosting its “Freak-o-Ween,” which features DJ Chris Style on the decks and DJ Kruz judging a costume contest with a $5,000 prize.

To mark the opening of an exhibit of his photography, “Destroyed,” electronic musician Moby will be signing books of his photographs from 6 to 8 p.m. Saturday at the Montserrat House. The reception also features an acoustic music performance.

Take advantage of a rare performance at Signature Theatre of Stephen Sondheim’s first musical, “Saturday Night.” The story, which went unpublished for 45 years, centers around four Brooklynite bachelors hatching a get-rich-quick scheme in pre-Depression Manhattan.