Mars Under the Tree

Mars is at opposition on Christmas eve!

This isn’t a close opposition. Our small neighbor won’t get bigger than 15.9” (that’s arc-seconds, not inches) — between a third and half the apparent size of Jupiter. But there’s some good news, too: it’ll be REALLY HIGH, just 10 degrees short of the zenith. If we get some steady air, you can slip in your shortest eyepiece and really crank up the magnification.

Closest approach is actually the week before opposition, on the 19th. But really, Mars should be good all month (plus January and most of February), so keep your scope ready to sneak a peek whenever the skies are clear.

This opposition is somewhat unusual in that we’ll be seeing Mars nearly equator-on. So we should be able to see both hemispheres fairly equally, and may even be able to see both polar caps at once. Mars will hit its equinox (autumnal for the southern hemisphere, vernal for the northern) on December 9, so the north polar cap will be very prominent while the southern cap will be quite small. Throughout December we should be able to see the hazy “north polar hood” gradually break up to expose the brighter polar cap beneath.

If you read about observing Mars, you’ll see a lot of advice about using filters of different colors to bring out specific details. Should you worry about that? The answer is no. If you have picked up a set of colored filters at the SJAA swap meet last month, then you’re all set — use them and see what you can see! But if you don’t have any, don’t feel like you have to rush out and buy some. I find that filters make only a subtle difference. Sometimes a colored filter will help me notice something I might not have noticed otherwise – but then after I remove the filter, I’ve always been able to see all the same features. What about telescopes? Do you really need a 7” Astro-Physics refractor?

Well, I won’t deny that it helps. If you happen to have one sitting around the house, by all means use it! But I’ve seen detail on Mars in an opposition less favorable than this one through my 4-1/4” f/4 backpacking reflector (think glorified Astroscan). Like most shallow skyobserving, the only rule is: Use What Ya Got.

There’s a naked-eye Mars show, too: on the night of the 23rd, Mars and the full moon have a very close encounter (a quarter of a degree). If you’re visiting relatives anywhere north of Portland, you can see an occultation.

I hope you all got a chance to see Comet 17/P Holmes (2007) last month. What a nice surprise it was to see a naked-eye comet suddenly grace our northern sky! Comets are frustrating for a columnist, because the best ones don’t give much warning — they suddenly appear, or flare up without notice. Email lists are the best bet for keeping track of events like that.

A few comets are more predictable, though. This month, periodic comet 8P/Tuttle is expected to brighten to naked eye levels (barely) by the close of 2007 when it comes within .25 AU of the Earth (a quarter of the distance from us to the Sun). It’ll be passing through Andromeda, crossing about seven degrees east of M31 on the 27th and 28th, then along the outskirts of M33 in the early evening of December 30th. (It actually goes right through M33, but that happens during our daytime.) M33 and 8P/Tuttle should actually be fairly close in brightness by then, so it might be an interesting sight. Google for Comet 8P/Tuttle for a more detailed finder chart.

It’s a good thing we have Mars and comets, because there’s not much else going on in the shallow sky this month. Jupiter disappears into the sunset by the middle of December. Uranus and Neptune hang around longer in the evening, but they’re not especially high or well placed. Saturn rises late in the evening and transits around 4 am. Venus continues its domination of the morning sky.