I really should do my winter sky observing in September. The only obstacle is having to get up before dawn. During the evening hours, we see the stars of late summer and early fall – Cassiopeia, the Summer Triangle, the Great Square of Pegasus. But as we sleep, the Earth turns and by 4 o’clock in the morning, Orion the Hunter and Gemini the Twins are high in the east and ripe for plucking with binoculars and telescope.
What a sight to see Orion beneath trees still green and in temperatures well above freezing. That was the view this morning when I stumbled out to see Comet Honda-Mrkos-Pajdusakova low in the eastern sky near the start of twilight. After a peek at the Orion Nebula, I aimed the 15-inch telescope to a spot just below the bright star Regulus and bingo! Using my lowest magnification of 64x the comet was a tight, bright ball of light with the most delicate, lovely ion tail streaming away to the west. Shining at magnitude 6.5 (just below naked eye limit), Comet Honda looked like a faint star wrapped in a bit of fuzz through 8×40 binoculars. Even a 25-second exposure picked up the telltale green color of cyanogen, a glowing gas found in the comas or atmospheres of many comets.
The comet will slowly fade over the next few weeks as it moves eastward in Leo. It passed closest to Earth back in August and is now pulling away with a current distance of about 75 million miles. For a map to help you find it, click over to this earlier blog.
The only snag to seeing the comet is its low altitude — only about 10 degrees or “one fist” high at the start of dawn 1 1/2 hours before sunrise. If you can find a place with a wide open view toward the east, you’re in business. While we may never get to see Comet Elenin post-breakup, Comet Honda makes for a solid stand-in.
In the same direction there’s a much larger phenomenon visible with the naked eye to those with dark, light-pollution free skies. Every fall when the moon has departed the morning sky, the “thumbprint” of the zodiacal (Zoh-DYE-uh-cull) light makes its appearance in the east just before the start of morning twilight for observers at mid-northern latitudes.
This large, oval or cone-shaped glow, which is composed of minute dust particles shed by passing comets, spreads through plane of the solar system called the ecliptic. In fall, the ecliptic is steeply tilted upwards in the east in the wee hours of morning, “lifting” the dim, diffuse zodiacal light high enough to clear the lower, hazy air and improve its visibility.
If you’d like to see it, anytime in the next week and a half is ideal, since the moon won’t disturb the darkness required to see this curious cometary remnant. If you miss it this month, you’ll have another chance in late October. The cone is widest near the eastern horizon in Leo and narrows as you direct your gaze upward and to the right. The best way I’ve found to spot it is to turn your head left and right while facing east and look for a large, soft haze similar to but a bit fainter than the Milky Way.
It’s a fun coincidence that Comet Honda, which is shedding dust as it departs the Earth’s vicinity, is making its own contribution to the zodiacal light, ensuring that future generations of sky watchers will always have this otherworldly sight to look forward to. To learn more about it, click HERE.
One final news note. NASA announced yesterday that the Upper Atmosphere Research Satellite (UARS) everyone including myself was so excited about last weekend fell back to Earth at 11 p.m. Central time Sept. 23 over the South Pacific Ocean not far from American Samoa. Any debris remaining from the burn-up is probably sitting at the bottom of miles of water. No sightings of the re-entry have been reported.