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Messier Marathon : What Really Happened?
Messier Marathon : What Really Happened?

Messier Marathon is a term describing the attempt to find as many of the Messier objects as possible in a single night. A marathon held on Saturday, March 17, 2007 promised the prospect of observing all 110 objects in one night. Let's see how Jeff Barbour made out...

Messier's 'Year in a Night' has come and gone and now you're left wondering why you didn't find all 110 on your first outing. The reasons are simple. Sky conditions trump everything, and the spot you chose to observe from introduces its own peculiarities. But you're tough enough to handle the truth. Even if you'd been observing from the surface of the Moon, you might have missed a few.

But let's start with that Moon idea first, shall we?

On the Moon, there'd be no trees and foliage to block the horizon. You'd be able to sweep the scope all the way across that 180 degree vault of the heavens and nothing would make an obstacle of itself. But a clear horizon is possible on Earth too. There are seas, mountains, and deserts enough that you could find the wide open spaces needed for a Messier Marathon. How wide open was your site? Probably more foliage than you'd care for.

But the Earth, unlike the Moon has other complicating factors as well. The Moon is free of atmospheric gases. There's nothing floating above the lunar surface to absorb, scatter, or disturb light in any way. From the dark half of the Moon, your fully dilated and dark-adapted eyes could capture starlight as faint as magnitude 8! How's that for seeing?

I'll bet you weren't going that deep where you were observing from—regardless of the horizon. In fact if you could see overhead stars to magnitude 5.5 without trouble, you were blessed with some pretty fine conditions! And if you weren't? That's one very good reason why you fell a few shy of 110.

Theoretically, if you could see stars to magnitude 8 unaided, you could also see more than 60% of the Messiers without any instrumentation whatsoever. But first you'd have to know precisely where to look, and more importantly what to look for! Distinguishing 8th magnitude anything's from stars might be a bit much to ask from those 1x7 binoculars you were born with. Besides, you'd need astronomical binoculars anyway if only to make out the other 40%. Meanwhile, a little extra magnification comes in useful when distinguishing stars from star clusters.

Bottom line: Seeing isn't finding, and sometimes finding isn't seeing!

Now let's get back down to earth again. Because the Earth has an atmosphere, there are some things you have to consider with or without that unobstructed skyline. First, even though the length of the day and night are roughly equal in March, the sky doesn't really start to get dark until astronomical dusk. Professional astronomers don't even think of arriving at the observatory until the Sun is at least 18 degrees below the horizon. Why? Because astronomical dusk doesn't start until 72 minutes after sunset! A marathon typically starts about one hour after sunset and may not end until half an hour before sunrise!

The deck was stacked against you from the beginning of the game.

During a Messier Marathon, you have to make some trade-offs—both ends of the night. Those trade-offs are between sky position and sky transparency. If you start your marathon too early, the sky is too bright to make out low average surface brightness galaxies like M74 in Pisces despite the fact that earlier than this M74 would be positioned higher in the sky where things normally show up better. But if you start too late, the Earth's thicker, more dust-laden atmosphere down low reduces contrast between the galaxy and background sky. Similarly challenging in this way is equally low average surface brightness Triangulum Galaxy M33. (Both galaxies have an average brightness of magnitude 13.9.)

So when is the best time to start?

That depends on sky conditions. A really transparent sky gives you more of an observing window. A poor sky can offer no observing window whatsoever! You have to nail it anywhere in between. So how was your sky?

One way to tell how things are shaping up is to turn your telescope on Polaris. Use whatever magnification will give you a one degree true field—that means roughly 60x (through most modern wide-field eyepieces). Keep checking for Polaris' companion until things darken enough to see it direct (without averting your vision). On a good night, you should just make out Polaris-B 45 minutes after sunset. Once you see Polaris-B, swing the scope around on Castor in Gemini. A clean split at the same magnification means the sky is nice and stable. Stability means less dust and light scatter nearer the horizon when you head off after the early toughies like M74, 110 and 33.

Having resolved Polaris and Castor you were toeing the starting line but not tensing any muscles. It was another 15 minutes before you were off and walkin' the night sky.

By 7:00pm however, you were listening for the start gun. Did you find 3.7 magnitude Eta Piscium unaided? Even so, you probably swept the sky nearby and found nothing? How'd you miss M74? Was the sky still too bright? Or did you move the scope in the wrong direction, say slightly south and west rather than north and east? Maybe your eyes weren't dark-adapted enough? Or perhaps M74 was much fainter than you remember? Did you double check the charts and try again? After a few more sweeps for M74, you probably decided to move on to M77. Funny, I don't remember M77 being that faint! Being the persevering sort, you returned once again to Eta and followed the star west until it sunk into the foliage.

Better luck next year!

The fact that you did find M77 was a confidence boost but the thought of missing one right out of the box let some of the heat out of your balloon. But you did push on determined to find the next three.

Although M31 was visible through that 9x50 straight-through Orion finder scope, M110 completely eluded you. Why? Again low sky position and faint average surface brightness. You found M32 for the same reason you found M77, that intense star-like core. Here's a lesson: bigger, despite being brighter, can be fainter. Over the next year of observing you may want to start challenging yourself by finding as many low surface brightness studies as possible. What's one way to do that? Get that scope out when the Moon is bright and look for studies you already know how to find under better conditions!

So the score was 3 to 2 in the first inning with a tough batter stepping up to the plate, M33. How'd you do there? Located some 30 degrees above the horizon 90 minutes after sunset, M33 should be well above the trees yet, due to the fact that there are few neighboring bright stars, tracking it down was tough! Although M33 is faint, you didn't stand a chance if you couldn't locate it in the sky. If not, next time around try this; M33 is roughly the same distance along a line extended from M31 through 2.4 magnitude Mirach in Andromeda. Keep in mind that you have as much of a chance of seeing M33 in that 50mm finder scope as at 60x through the big dob. Over the next year, see how many Messiers you can spot through the finder alone. Only about a dozen or so will elude you, more if you're not sure what to look for at low power.

Over the rest of the evening things went well enough, except that you may have misidentified a few of the Coma-Virgo galaxies. Did you feel tempted to gloss over a few? Or did you painstakingly pick your way through those 14 galaxies without a hitch? Here's where self-honesty comes to play. One of the greatest skills you'll ever learn in observing is how to tell the difference between really finding something or 'just guessing'. If knowledge is power, then guesswork is a blown fuse.

After midnight things became sheer observing pleasure but later came rosy-fingered dawn and the delight she took in veiling the stars. Like the evening before, there were three tough Messiers to track down at magnitude 9.4, M72 is the faintest of all Messier globular clusters. Meanwhile nearby M73 like M40 in Ursa Major is one of those 'anomalous' discoveries that looked like a 'faint fuzzy' in Messier's spindly long-focus, small-aperture refractory telescope. Then there was that brighter M30 globular cluster struggling to clear the tree line ahead of dawn's later light.

You probably had trouble finding M72 simply because it's so faint especially if you were rushing or using a smaller instrument. You'd miss M73 primarily because it is a tiny group of easily overlooked 10th through 12th magnitude stars. M30 was purely a matter of observing locale although navigation in the hinterlands can be a bit of challenge as well.

So how'd you do? Triple-figures would be a great start! But frankly the real win here was the fact that somehow despite the rush and technicalities of observing you spent a whole night with good friends under the Night Sky.

And that's what it really was about, wasn't it?

April 2007

Details
Date Taken: 06/02/2011
Author: Jeff Barbour
Category: Archives

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