Catch Comet Lemmon While You Can

If you honed your observing chops on Comet PANSTARRS this spring, consider dropping in on Comet Lemmon, now returning to the dawn sky. Southern hemisphere observers saw this comet at its brightest in March when it briefly became dimly visible with the naked eye. It’s now faded to around magnitude 6, the same as the faintest stars you can see under a rural sky.

Because it’s been “vacationing” in the southern constellations, northerners have had to wait until now to see it.

Comet Lemmon with gas (left) and dust tails on April 24. Click to see a short movie showing rapid changes in the comet's tail in 25 minutes. Credit: Gerald Rhemann
Comet Lemmon with gas (left) and dust tails on April 24. Click to see a short movie showing rapid changes in the comet’s tail in 25 minutes. Credit: Gerald Rhemann

Like PANSTARRS, C/2012 F6 Lemmon is visible in modest-sized binoculars (7x35s, 10x50s) as a small, fuzzy ball of light with perhaps a faint tail. Watch for it to slowly track along the eastern side of the Great Square of Pegasus for the remainder of April and May. It competes with twilight low in the eastern sky this week but gradually becomes better placed for viewing as May unfolds. The best time to look is about an hour and a half before sunrise now and 2 hours before sunrise by mid-May.

The waning moon interferes some until around May 5. On the 6th, watch for the thin lunar crescent moon to pass 8 degrees below the comet. Around that time, we’ll finally get a good view of Lemmon in a dark, moonles sky just before the start of dawn.

On May 6 a beautiful thin moon will be near Comet Lemmon at dawn. This map shows the sky about 1 1/4 hours before sunrise. Stellarium
On May 6 a beautiful thin moon will be near Comet Lemmon at dawn. This map shows the sky about 1 1/4 hours before sunrise. Stellarium

Comet Lemmon will fade from naked eye limit to a dim binocular smudge of 7.5 magnitude  by mid-May. If you have a telescope, look for a pair of tails – a short, diffuse one of dust particles and the straight, streak-like gas tail fluorescing in the sun’s ultraviolet light. The tails point approximately to the south-southwest. Catch this comet while you can!