There are chances on consecutive days to catch a crescent moon within 24 hours of a new moon—a rare thing indeed. Here are the details.
First, look about 45 minutes before sunrise on Tuesday, Dec. 31, to catch the old crescent moon very low in the east-southeast. Binoculars will help you spot the rising moon about 20 degrees to the lower left of Antares. Once you spot the lunar crescent, note the time, and calculate the interval remaining until the new moon, which occurs Jan. 1 at 3:14 a.m. PST. From Southern California, crescent sightings will occur 21 hours before new.
The next chance to see the moon occurs at dusk on Wednesday, Jan. 1. As noted above, the new moon occurs early that day. Using binoculars, start looking for the thin young crescent moon, very low in the west-southwest, about 25 minutes after sunset. You’ll need to observe from a place with an unobstructed view of the brightest part of the twilight sky, directly above the recently set sun. From Southern California, the moon will appear within 8 degrees to the lower right of Venus. If you spot the moon, take note: Only a few observers have succeeded in seeing the moon so close to new.
If you see the easier old moon at dawn on Dec. 31, and also see the very challenging young moon at dusk on Jan. 1, then you’ll have seen opposing crescents on consecutive days, which is really special. Be sure to let us know about it! Include your location, times and details of your observations in an email to email@example.com. And if you know anyone in Hawaii, pass the word: Sky-watchers there will have an easier time getting a Jan. 1 sighting, so it will be easier for them to catch the old crescent at dawn on one day, and the young crescent at dusk on the next.