View Full Version : Spotting the December New Moon while it is Occulting Mars

2010-Nov-24, 08:47 PM
On December 6th some observers will have an opportunity to spot the New Moon while it is little more than a day old at the same time it is occulting Mars. The Dark Moon will be in geocentric longitudinal conjunction with the Sun on 2010 DEC 05 at 17:36 UT (11:36 CST). Mercury will serve as a guide star about 6° to the upper left of the Moon during the evening of the 6th.

I’ve made a graphic previewing the southwestern sky from Chicagoland after sunset on December 6th. It should well serve most North American observers. I’ve also created a North American graze map for the Mars occultation, and specific occultation info for observers at Chicago’s Adler Planetarium. They can all be seen by clicking: http://www.curtrenz.com/astronomical then going to the Moon page.

If you would like Mars occultation or graze data for a specific location, please reply to this post with a longitude, latitude, time zone and elevation above sea level.

Photos and descriptions of the December New Moon and Mars occultation would be welcome additions to this thread. Please include the date, time, time zone and location. Good Luck!

Below is a photo I took from Arlington Heights, Illinois after sunset on 2008 DEC 28 of a 1.5-day-old Moon with Venus at the top and Mercury in the center.


2010-Dec-05, 08:17 PM
The December 6th observation from Chicago's Adler Planetarium of the occultation of magnitude +1.3 Mars by the 1.6% illuminated waxing crescent Moon may be something of a challenge, but less so than for many other locations. I calculate that the immersion of the center of 3.9-arcsecond Mars into the Moon’s dark limb will occur at 16:31:59 CST, which will be only 12 minutes after sunset at the Adler. Optical aid will almost certainly be required during bright twilight, despite Mars being at first magnitude. The emersion will occur after moonset.

Please be extra careful, if trying to observe while the Sun is still out. My only occultation observation occurred on 1958 JUN 18. It was serendipitous. With my 3-inch refractor I was seeking to spot a quite young Moon low in the west moments after sunset, when I realized the Moon’s dark limb was approaching a star. I didn’t learn which star it was until I wrote an occultation program 40 years later. It was magnitude +3.6 Lambda Geminorum. Magnitude +1.3 Mars should present a somewhat easier target for Chicagolanders on Monday.

At the time of the immersion at the Adler, here will be Mars’ coordinates.

RA 17:56.5
Dec S 24° 17’

Horizontal (Alt-Azm)
Azm 230.1° (6.1° to the right of southwest)
Alt 5.7° (atmospheric refraction corrected)

Good luck, folks. Your reports are much anticipated!

2010-Dec-19, 01:50 AM
APOD (http://antwrp.gsfc.nasa.gov/apod/ap101210.html) image.