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  • Rapt in Awe

    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

Events: March 2010 – Venus takes center stage, west and a marathon night

The date I’m circling on my calendar for this March is the 16th – that’s when I want to go to my favorite spot that has a clear western horizon and catch the sun setting practically due west, Venus emerging in the early twilight, and with luck, the thinnest of crescent moons next to it. Then I’ll wait another hour and see if I can detect the ghostly glow of the zodiacal light, and for the rest of the night – with telescope handy – I have my choice of the entire catalog of Messier objects, something that can only happen in mid-March!

Of course, the only thing magical about March 16 for me is the combination of Venus and the crescent moon. Truth is, this combination will be available in an easier to detect form the next night as well – and Venus is available in the western sky all month! But on March 1, half an hour after sunset, it is just 4 degrees above the western horizon. By March 15 it is nearly twice as high, half an hour after sunset, making it much easier to see. By the end of the month it is more than 11 degrees above the horizon at that time, and if you can find it in your binoculars, you’ll see another bright “star” right below it in the same binocular field – that will be fleeting Mercury. Mercury first puts in an appearance about the 20th of the month, but doesn’t really become easy to see until the last days of March.

This chart is good for mid-northern latitudes. The exact position of Venus and the Moon will change depending on your location on Earth. Do not look until after sunset and be especially careful when using binoculars to wait until the Sun is well below the horizon. Click image for larger view. (Chart prepared from Starry Nights screen shot.)

If you want to see both Venus and the crescent moon on March 16, first notice exactly where the Sun sets. Wait 10 minutes, then start scanning that area of the horizon for a bright “star.” Venus will be easier to find than the crescent moon, though on the next day the moon will be higher and easier to find. If you find Venus, the Moon will be to the right (northward) and lower. It may just barely fit in the same binocular field, but most likely you’ll have to let Venus slip out at the upper left and be looking for the moon to come into view in the lower right.

The zodiacal light is available any time of year, but is much easier to detect in the evening sky about 80 minutes after sunset in February, March, and April – with March being the best. For more details about what it is and how to observe it, see this posting.

As to seeing every one of the objects in the Messier catalog, you should first understand that only a few of these are visible to the naked eye, the most famous being M45, the Pleiades. The Astronomical League classifies 42 of the 110 Messier objects as “easy” to find with ordinary binoculars – assuming you know just where to look. For the rest you really need a small telescope, or large astronomical binoculars. During most months at least some of them are obscured because the Sun is in the same section of sky as they are. They can also be drowned out by the light of the moon. But in mid-March, each year, nearly all Messier objects are far enough away from the Sun to be seen, although two of the 110 (M74 and M30) are still so close to the Sun that they are very difficult targets.

Since the mid-1980’s this idea of prime time for Messier objects has led to an extraordinary “sport” of sorts where amateur astronomers pick a night in mid-March, and stay up all night with the avowed goal of finding each of the 110 Messier objects. They call it a Messier Marathon. Frankly, I have never tried it and the idea doesn’t have much appeal to me because when I find one of these fascinating objects I like to stay with for at least half an hour. So the most I would see in a 12-hour night is a measly 24! Still, I like the idea of staying up all night and looking at different Messier objects as our spinning Earth brings each into view.

This year the key date for the Messier Marathon is March 13. That’s a Saturday night, and there will be no interference from the Moon. So if this is your thing, hope for good weather. As with all astronomical events, even when they happen every year, it is still rare when the weather and your personal schedule cooperate so you can enjoy them fully. Of course, if work is no issue you don’t have to be strict about the date. Any time within a week either way gives you a good shot at finding nearly all of the Messier objects in a single night.

Oh – and don’t forget the equinox on March 20th.

I love the equinoxes for their long nights, moderate weather, and sense of cosmic balance. This is the time when the Sun is half way in its journey north – or in September, in its journey south – and is rising and setting very close to due east or west. This year the vernal equinox occurs on the afternoon of March 20th in my Eastern Time Zone and that means sunset on that day is pretty much due west. OK, technically it’s a bit off target, but astronomers are used to “close enough being good enough.” Even Polaris, the “pole star,” is nearly a degree off the north celestial pole, but most of the time we treat it as if it’s right on. If you’re new to observing the night sky, this is a great time of year to get your bearings at your favorite observing location. Watch either the sun rise or the sun set and note the landmarks near it – that way you’ll have a quick way to identify the eastern or western point on your horizon. (You could use a GPS instead, but I’m an incurable romantic and would rather use the motion of Earth and Sun. )

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