SJAA

Ephemeris

The Shallow Sky

Akkana Peck


As May opens, Mars is a week past opposition, and May 1 will be its closest approach to the earth, only a little over half an AU from us (i.e. Mars is only half the distance of the sun right now) and showing an apparent diameter of just over 16", about the same size as Saturn. It's visible all night, and the weather should be improving -this is a great time to roll out that telescope and take a look at the red planet.

How is it that closest approach is a week past opposition? The eccentricity of Mars' orbit (the same irregularity which makes some Mars oppositions so much closer than others) is the culprit.

I've collected links and information on observing Mars at www.shallowsky.com/mars.html There's a new version of Mars Previewer out (still free, unfortunately only available for Windows); it's reportedly much better than the old version, though some people have had trouble installing it. Get it at marspreviewer.cjb.net (not the skypub site where the old version was).

What features should you look for on Mars? The polar cap has been hit-and-miss; it's reported to be unusually small this year, but apparently polar haze or clouds sometimes make for a very visible polar whitening, as some SJAA observers have reported. Bright Hellas is prominent (don't mistake it for the polar cap!), as is Chryse. Quite a number of dark features have been reported, including the obvious Syrtis Major, Acidalia, and Mare Erythrium. One observer reported seeing relatively subtle features including Sinus Sabaeus/Sinus Meridiani with a 4.5" reflector. Don't give up just because you don't have a big or expensive telescope!

Here are some recent comments from SJAA observers:

Bill Arnett: "Acidalia and the north polar cap were obvious as were some white areas on the equatorial parts of the limb which I interpreted as clouds (though one might have been Hellas). Also saw a large dark feature south of Acidalia which is probably Mare Erythraeum and its two "bays". South of there I thought I caught a glimpse of a white region from time to time; that would be Argyre. Mars is fun when it's close to opposition!"

David North: "Something is definitely showing where the polar cap should be ... it's pretty obvious. Mare Serpentis is pretty easy, as is Iapygia Viridis, but Deltoton Sinus is not. "Sinus Sabaeus/Meridiani/Margeritifer is thicker than pictured in Mars Previewer, and Acidalium more pronounced... but both Niliacus Lacus Boreum are very slight if at all showing. "Mare Erythrium seems bifurcated from Vulcani Pelabgus rather than joined as shown."

Bill Arnett again: "I caught most of the things Dave mentioned and they seemed pretty much as he described them except that I didn't think I was seeing as far south as Erythraeum. But I did get a good look (i.e. I saw it clearly for a few seconds several times over a period of half an hour) at Oxla Palus. It is a long linear feature going from Margaritifer up toward Cydonia. I didn't see The Face, though :-)"

Tired of Mars yet? Well, there are a few more planets to look at. Venus is still high in the sky after sunset, nearly 40 degrees up and magnitude -4. Its phase decreases from gibbous to last quarter. On May 5th, the largest asteroid, 1 Ceres, will pass seven tenths of a degree north of Venus. Another asteroid, 4 Vesta, is also worth hunting down near the Cancer/Leo border, at magnitude 8. The May issue of Sky & Telescope magazine has a good finder chart for Vesta and many other asteroids (but not Ceres, oddly enough).

Pluto, back in its normal position as farthest planet from the sun, reaches opposition on the 31st, in Ophiuchus. Use a finder chart or planetarium program to locate and identify the magnitude 13.7 object; the one in the RASC Observer's Guide is a good one.

Jupiter moves into the dawn sky in the latter half of March. Uranus and Neptune, too, are most easily observed in the predawn hours; they're in Capricornus and bright enough (magnitudes 5.8 and 7.9, respectively) to be found with binoculars.

Mercury and Saturn are both too close to the sun this month for easy observation.

Don't forget the lunar occultation of Regulus, just past sunset on May 21st! It should be a pretty event even in binoculars or a small telescope.


Akkana Peck; last updated: October 04, 2007 Prev Next