SJAA Ephemeris January 2010 | SJAA Home | Contents | Previous | Next

The Shallow Sky

Just another speck

Akkana Peck


Mars is at opposition at the end of January! So Mars season is in full swing now and continues for the next few months.

But before you get too excited, I have to caution you: this opposition is about as small as they come. Mars is near aphelion, its farthest point from the sun, and the closest we’ll get to it, on January 27, will still be 61.7 million miles (.66 AU) away. That means Mars will grow to 14.11” (that’s arcseconds) at its biggest.

For comparison, in the close opposition of 2003 Mars grew to 25.1”, almost as big as Jupiter, since it was only (only!) 34.6 million miles away. If you’re a fan of the songs at, you might say the planet is “just another speck.”

But I don’t mean to sound too discouraging. 14.11” isn’t that much smaller than Saturn’s disk, and only 2” smaller than the 2007 Mars opposition. We should still be able to see plenty of detail. And the good news is that it transits high, 75°. So if you get a steady night, dust off those short eyepieces and barlows and throw all the power you’ve got at Mars. I’ve gotten some great Mars views during past winter oppositions even when the planet’s disk was small.

Mars keeps its northern hemisphere tilted toward us during this pass. Right now, it’s spring in Mars’ northern regions, which is good news for us: it means the dust storms which plague some Martian oppositions shouldn’t be a problem this time, since the dust storms usually don’t kick up until summer.

What can you see? Well, during the actual opposition on the 27th, Mars will have its “boring side” pointed toward us: the Tharsis plateau, with its three volcanoes, as well as the even bigger volcano, nearby Olympus Mons.

You’d think the biggest volcano in the solar system would be something to see, wouldn’t you? But unfortunately, to observers on Earth it’s almost invisible. What you might see is a white or faintly bluish haze around the middle of Mars’s disk – orographic clouds created by wind flowing up the slopes of the volcanoes, just as Mount Hamilton often has clouds near it when the rest of San Jose is clear. Blue or green filters are said to aid in seeing orographic clouds on Mars, but personally I don’t usually find they help much. Try ‘em if you’ve got ‘em, otherwise don’t worry about it.

If you start early in the evening of the 27th, before 7pm, you should be able to see dark areas on the eastern limb – Acidalium and Niliacus Lacus in the north (don’t you love Mars nomenclature? I sure do!) and Erythraeum in the south.

As the evening progresses, those areas rotate away and Tharsis rotates in, but you should be able to see some darkness on the southern limb of the planet – Sirenum and Aonius – and you may be able to make out the slightly darker smudge of Arcadia in the north.

Mars’ day is 37 minutes longer than ours. So the feature you look at tonight will be in the same place on Mars 37 minutes later than it was tonight. In the days following opposition, Acidalium, Niliacus Lacus and Erythraeum will be visible progressively later, while the hours just after sunset will offer a peek at Sinus Sabaeus and Sinus Meridiani.

But I’ll talk more about those features next month. For now, just work on seeing anything at all on Mars. Our small red neighbor is subtle at the best of times, and seeing detail takes practice. I find it takes me a few weeks each opposition before I’m seeing much detail on Mars.

And take breaks now and then – there are a few other things to look at too. Saturn is visible in January’s late evening skies, rising around 10 p.m. That means it doesn’t transit until the wee hours of the morning, but when it does it’s a bit over 50° up. We should have a good view over the next few months. The rings are tilted about 5°.

Uranus is visible in the early parts of the evening, but catch it as soon as it gets dark, before it gets any lower. Neptune and Pluto are already too low to catch, as are Jupiter, Venus, and Mercury.


Previous | Contents | Next