You know the season is shifting. As the stars come out, the Big Dipper standing on its handle in the northeast is now as high as Cassiopeia standing on end in the northwest. The Dipper is rising into spring and summer, and Cas is descending from its high showing in fall and winter.
On Friday morning the 13th, the last-quarter Moon shines to the left of Saturn and the head of Scorpius before and during dawn.
The eclipsing variable star Algol should be at minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours tonight centered on midnight EDT; 9 p.m. PDT. Algol takes several additional hours to fade and to re-brighten.
Before and during dawn Thursday morning the 12th, the waning Moon poses near Saturn, as shown here. Look for Antares below them.
Jupiter this month forms a big, more-or-less equilateral triangle with Procyon and Pollux. Face southeast soon after dark, and Procyon is to Jupiter’s right. Pollux is high above them.
Procyon is also part of the slightly larger Winter Triangle just to the west, also equilateral. Its other stars are orange Betelgeuse and bright Sirius below.
Ganymede, Jupiter’s biggest moon, enters onto Jupiter’s face at 10:10 p.m. EDT and exits at 1:47 a.m. EDT. Its black shadow trails almost three hours behind, crossing Jupiter from 1:05 to 4:43 a.m. EDT. (Subtract 3 hours to get Pacific times; this event is more convenient for the West Coast.)
Now that the Moon is gone from the early-evening sky, have another look for Comet Lovejoy! It’s crossing Cassiopeia and still 6th magnitude, this means it will be visible in most decent sized telescopes, fading more slowly than predicted. Plan to go out right after dark. See article and finder chart: Comet Lovejoy Shines On.
Little Mars has sunk to 6° below Venus now in the west at dusk. The gap between them will continue to widen until Mars finally becomes lost in the sunset in late April.
Daylight-saving time begins at 2 a.m. Sunday morning for most of the U. S. and Canada. Clocks spring ahead one hour.
As the stars come out at this time of year, look due south for Orion standing upright at his highest. As night deepens, dim Lepus, the Hare, emerges under his feet. Below Lepus is Columba, the Dove
Full Moon (exact at 1:05 p.m. Eastern Standard Time). This evening the Moon shines below the dim hind feet of Leo.
And another! Io partially eclipses Ganymede with its shadow from 1:35 to 1:46 a.m. Friday morning EST. Ganymede will dim by a full 1.0 magnitude at mid-eclipse. They’re both to Jupiter’s west – with Callisto in the background between them! Callisto is normally 1.1 magnitude fainter than Ganymede (which is the one appearing closest to Jupiter). But at mid-eclipse Ganymede will look almost identical to Callisto, with Io clearly outshining them both.
A challenge for North Americans as twilight turns into night: Distant Uranus, magnitude +5.9, glimmers just below Venus, which is 8,000 times brighter at magnitude –3.9. Use good binoculars or a telescope. At the time of nightfall on the East Coast, Uranus is 0.3° below Venus. By nightfall on the West Coast it’s 0.5° below. Nothing else of that brightness is that close under Venus.