We see a lot of changes in the planets this month: We lose two, gain one, and two planets hold steady in the night.

The elusive planet Mercury appears in our skies for the first time in 2013, low in the west at dusk for much of the month.

You might be able to catch Mercury as early as Friday, since it blazes away at minus 1.15 magnitude. Look west as dusk settles in around 6:40 p.m.; Mercury is the brilliant point in the west-southwest. In early February you have a narrow slot to see Mercury because it sets by 7 p.m.

By Feb. 7 you have a better shot; Mercury emerges from the twilight around 6:40 p.m. and then does not set until 7:30 p.m. The planet still shines at minus 1 magnitude. On Feb. 11, the moon is a convenient guide to finding Mercury. Look for the early crescent moon around 7:20 p.m. in the west. Mercury is the bright light just to the lower left of the moon. Down below Mercury, and so faint that it may require binoculars, look for the faded planet Mars.

On Feb. 16, Mercury is at its greatest "elongation" from the sun, which means it appears as far as it ever gets from the sun in our sky. This should be the best time in 2013 for viewing Mercury. The days are getting longer, so the planet will not emerge from the sunset glow in the west till about 7 p.m., but will not set till 7:45 p.m. Mercury now shines at minus 0.4; not as bright as earlier in the month, but it should be striking if you catch it as it is about to set. After this, Mercury fades fast.

To look for Mercury, make sure you have a flat western horizon. It’s often said that only one person in 1,000 sees Mercury and knows it; so if you catch Mercury in February, you can join that elite club.

Early in the month, look for Mars in the west-southwest at dusk, setting by 7:30 p.m. It may take binoculars to spot the red planet in the murky dusk glow. Your best chance of spotting Mars will be around Feb. 8, when much brighter Mercury is a mere half a degree (the width of a full moon) above Mars. By the end of the month, Mars is finally lost in the sunset, and won’t be seen again until June.

Venus rises in the east-southeast at 6:23 a.m. on Feb. 1, and is so bright that you might spot it for few moments before day breaks at 7 a.m. By Feb. 14, the planet rises at 6:30 a.m. and you’ll have only about 15 minutes to see it before daybreak. After that, Venus is lost in the sun until the evening skies in May.

Jupiter has been the brightest dot of light in the evening sky for the past few months and continues to fill that role in February. In early February, look for Jupiter almost exactly overhead at dusk. In early February, the planet sets in the west around 2:30 a.m. By the end of February, look for Jupiter high in the west at sunset; it will set just before 1 a.m. Jupiter remains the brightest dot of light in the February evening skies.

Jupiter shines between two star clusters: the tiny dipper of the Pleiades and the open V-shape of the Hyades (also known as the face of Taurus the Bull). Jupiter seems to form a pair with the star Aldebaran, the eye of Taurus the Bull, but it’s a lopsided pair; Jupiter is many times brighter than Aldebaran.

On the night of Feb. 17, look for the first-quarter moon less than three degrees away from Jupiter. This will be a lovely sight, spanning from the Pleiades to the orange star Aldebaran in the eye of Taurus, with the moon and Jupiter in between. Because the moon moves so fast, you can see the difference between Jupiter and the moon in the course of the single evening. At dusk on Feb. 17, when Jupiter and the moon appear out of the twilight overhead, they will be about three degrees apart, or a little more than the width of your middle finger held at arm’s length. By the time Jupiter and the moon set around 1:30 a.m. early on Feb. 18, they will be only one degree apart.

In early February look for Saturn rising at 12:40 a.m., as the brighter light of Jupiter sinks in the west. In early February, Saturn will be almost exactly overhead at dawn. Saturn rises a little earlier each night, and comes up by 11 p.m. at the end of February. At the end of the month, Saturn will be almost halfway down in the west at dusk.

Throughout the month, Saturn forms a near-right triangle with two bright stars above it, Arcturus, brighter than Saturn, and Spica, dimmer than Saturn. Another way to locate Saturn this month: Look for the famous claw of Scorpius the Scorpion in the early morning sky; Saturn is the average-bright dot of light about 20 degrees (the width of two of your palms held at arm’s length) above the claw. Look for the third quarter moon next to Saturn early on Feb. 3.

FEBRUARY SKY MAP

This map is good for 11 p.m. in early February and 9 p.m. at the end of the month.

The map shows one of those rare cases when both the Big Dipper and Cassiopeia are in the sky at the same time. These two are on near-opposite sides of the North Star, so you always have one or the other in the sky, but now you can briefly catch both.

The Southern Cross is up in the south-southeast by 1:45 a.m. in early February and before midnight by the end of the month.

———

Mike Shanahan is director of education, exhibits and planetarium. For more information, go to www.bishop­museum.org/planetarium/planetarium.html.