Bob Moler's Ephemeris Blog

Ephemeris for Thursday, October 10th.  The sun will rise at 7:51.  It’ll be up for 11 hours and 14 minutes, setting at 7:06.   The moon, 1 day before first quarter, will set at 11:34 this evening.

Comet ISON is finally bright enough to possibly spot in binoculars.  It seems to be between  10th and 11th magnitude, at the very limit of a pair of binoculars.  Since it’s physically close to Mars, it’s close to Mars in our sky.   Tomorrow morning it will be less than a binocular’s field of view to the upper left of Mars.  Also don’t confuse Mars with the brighter star Regulus below Mars.  In color photographs Comet ISON is showing a green coma or head a sign that the nucleus is spewing, among other things, cyanogen, a poison gas and/or diatomic carbon.  Don’t worry, Comet ISON will not get anywhere close to the earth.  The last comet I saw with a green head was Comet Hyakutake which came within 10 million miles of the earth in 1996.  The comet’s head is pretty much a vacuum.  We’ve flown spacecraft through them before.  It’s the dust grains we worry about.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Tuesday morning (Oct 8) I went out to try to spot Comet ISON with my 10X50 binoculars at 5:30 a.m. and was unsuccessful.   I think I had two problems.  First I am located 5 miles southwest of Traverse City, and though I had a good view to the east, I was hampered by the lights of the city.  Also there may have been some zodiacal light.  It’s the prime time for zodiacal light in the morning and the inbound comet is following close to the ecliptic line where the zodiac constellations reside.   Wednesday morning I’m setting up my 11″ Dobsonian reflector.  Let’s see what I can see.

Wednesday morning (Oct 9)  I had my 11 inch Dobsonian trained on the comet’s location.  But the light from Traverse City south was overpowering.  Let’s see plan C is to go south to outflank Traverse City.   We have a member of the Grand Traverse Astronomical Society who lives about 9 miles south of me.  The only town he has to the east, in the direction of the comet is 9 1/2 miles, the little town of Kingsley.  So that’s where I’m going tomorrow morning if it stays clear.  It’s expected to be.

Comet ISON and Mars at 6 a.m. for 7 days starting October 10, 2013. Created using SkyCharts (Cartes du Ciel).

Don’t expect a tail.  The head if Comet ISON will be hard enough to see.  The yellow line is the ecliptic, the projection of the earth’s orbit on the sky.  Most planet orbital planes lie close to the earth’s orbital plane, so are usually seen near it.  The star marked α is Regulus the brightest star in the constellation of Leo, and about the brightness of Mars.

Spaceweather.com has images of the comet.