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Seeing Mercury, Finding it in Earth's sky
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post Jul 21 2008, 08:59 PM
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QUOTE (ugordan @ Jul 21 2008, 12:43 PM) *
...observers said it just has a touch of a soft coppery hue.


Maybe so. It's really hard to get a view of Mercury without a whole lot of sunset/sunrise skyglow, though (very favorable elongations aren't that common), and that's often reddish; might be predispositioning the observer's impressions. The last good look I had through a scope against a reasonably dark sky seemed brownish-gray to me; darker then the Moon, anyhow. Your colors seem reasonable, Gordan.


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ugordan
post Jul 21 2008, 09:09 PM
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I think I actually only saw Mercury once in my lifetime, about a year ago. It wasn't through a scope but naked eye after sunset. It definitely looked more brownish than Venus which hanged somewhat higher in the sky, although it was twinkling at the time so I wasn't sure if that was it or some star.

Yes, it's hard to catch that thing in favorable viewing conditions!


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PDP8E
post Jul 21 2008, 09:21 PM
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QUOTE (ugordan @ Jul 21 2008, 04:09 PM) *
Yes, it's hard to catch that thing in favorable viewing conditions!


AGREED! I have seen it 4 times in over 50 years and only once through a telescope!
You have to plan - plan - plan - and then it only 'hangs' around for a few minutes.
The position in the sky (near the horizon, near the sun) is bright and dusty and has the biggest depth of atmosphere to look through). Winter is the best, but get to a latitude that favors Mercury's span from the sun.

Telescope observation: The limb looked less 'yellow' than Venus -- it seemed tawny, brushed metallic - no features - wavering in the atmospheric disturbances

Good Luck catching mercury!


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post Jul 21 2008, 09:21 PM
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Oh, big-time, man. In fact, the apparition I referred to was in Montana back when I was a kid: nice dark sky, no light pollution, and it actually rose something like two hours before sunrise. Beautiful half-lit appearance through a 2.4 inch refractor, brownish-gray.

I've never had a better view since. The damn thing is elusive. Legend has it that Galileo never saw it and bemoaned the fact on his deathbed, but that's rather doubtful.


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Stu
post Jul 21 2008, 09:45 PM
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I'm really lucky, in that I see Mercury quite easily and regularly from here; Kendal sits in a kind of natural "bowl" in the South Lakes landscape, with low hills rising up around it, giving a nice flat horizon to the west. So whenever Mercury puts on an evening show and is at its best, up to the ruins of Kendal Castle I go, and Mercury just pops out at us, glinting above the treetops on the hill opposite.


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post Jul 21 2008, 09:50 PM
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Cool! smile.gif

Yeah, northerly latitudes help a LOT for favorable viewing geometry. It's not worth a damn down here in LA, to say nothing of the light pollution, smog, people occasionally shooting at you, etc. Heck, I'm lucky to spot Jupiter.


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JRehling
post Jul 21 2008, 11:23 PM
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Boy, I've had better luck than a lot of people. I've probably seen it at twenty or so elongations, and as many as four times during one of those. I took my only picture of it looking down a San Francisco street where it was so low that I literally had to wait for a bus to get out of the way. With Mercury, brightness per unit surface area is never the issue, at least.

I also spotted it at least once in the east where it was the brightest object in the entire sky. No Sun, Moon, Venus, or Jupiter. I think it's an interesting (open, AFAIK) exercise to determine how many objects are capable of being the brightest object in the sky, assuming clear skies, a flat horizon, no comets or freakishly close asteroid passes, etc.

And then there was the night I found all seven planets through my telescope, looking at each in the order it lies from the Sun, with the Moon spotted in between Venus and Mars.
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post Jul 21 2008, 11:37 PM
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Yes, it can be surprisingly bright; I think the brightest stated magnitude I've ever seen for it is -1.8. Unfortunately, that's usually against a yellow sky at the end or beginning of an apparation, so getting a good read on the actual surface color is difficult in the extreme.

Man, JR: twenty times? You're good! smile.gif I've actually given up on seeing pretty much anything from LA these days. I live just a few blocks from the Staples Center, and half the time they've got spotlights piercing the haze/smog right at sunset & beyond; it's horrible. Need to get some time to drive out to the Mojave & really see the sky again, though will probably have to go at least 200 miles to escape the bloody light (and other) pollution from this place.


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ugordan
post Jul 21 2008, 11:40 PM
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Yep, it was pretty bright when I saw it, otherwise I'd have never seen it - was riding in a bus actually and just looking west in a clear late winter (I think) night. It was pretty neat, I suspected it to be Mercury, but had to check a sky map nevertheless. It would be great to see it through a scope next time...


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post Jul 21 2008, 11:45 PM
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It's worth a look. You can almost see what look like large albedo features when the air isn't churning (not often given its proximity to the horizon), but it's tantalizing. IIRC, Dollfus published the first maps of Mercury many years ago, but he is a very patient man with access to a rather large telescope (Pic du Midi Observatory). Wouldn't be practical at all for most amateurs.


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Bjorn Jonsson
post Jul 22 2008, 01:05 AM
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To add to the discussion, in my opinion Mercury actually *is* pretty easy to see if you know roughly where to look. It's really bright - the problem is the relatively bright background and also trees, buildings, hills/mountains etc. get in the way. I have seen it several times with the naked eyes but not yet through a telescope (not counting binoculars). The most memorable sighting came several years ago when I saw Mercury, Venus, Mars, Jupiter and Saturn all in the sky at the same time.
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post Jul 22 2008, 01:15 AM
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QUOTE (nprev @ Jul 21 2008, 03:37 PM) *
Need to get some time to drive out to the Mojave & really see the sky again, though will probably have to go at least 200 miles to escape the bloody light (and other) pollution from this place.


48 miles, dude.


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David
post Jul 22 2008, 02:11 AM
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QUOTE (nprev @ Jul 21 2008, 09:21 PM) *
The damn thing is elusive. Legend has it that Galileo never saw it and bemoaned the fact on his deathbed, but that's rather doubtful.


The story is most often told of Copernicus. See here and, in a lighter tone, here.

As the first article's author hasn't bothered to translate Copernicus' Latin (in 1892, I suppose most astronomers were expected to know a little), I'll offer a provisional and not highly accurate translation:

QUOTE
For Nature has denied that benefit to us who inhabit a more numbing region, where the clarity of the atmosphere is very rare, and moreover, because of the great obliquity of the sphere, it very rarely permits one to see Mercury.

On account of this, this planet tormented us with many detours and work, for us to investigate its wanderings. We have borrowed therefore three positions out of those which were carefully observed at Nuremberg.


And the last Latin quotation is from Gassendi, not Copernicus:

QUOTE
You wonder why you can't see any observation about Mercury here; but he himself ascribes the cause to the airs or fogs which the Vistula pours out; and likewise to the obliquity of the sphere, which 'very rarely', he says, 'permits one to see Mercury'.


French is certainly much better known than Latin, and my efforts at French will doubtless be corrected (if not mocked) by the French-speakers on this board; but for the sake of completeness, I translate Arago's further transformed characterization in this Telephone game:

QUOTE
Copernicus' sad comment that he would go down to his grave without ever having found the planet.
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mchan
post Jul 22 2008, 02:33 AM
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QUOTE (JRehling @ Jul 21 2008, 03:23 PM) *
I've probably seen it at twenty or so elongations, and as many as four times during one of those. I took my only picture of it looking down a San Francisco street where it was so low that I literally had to wait for a bus to get out of the way.

I've seen it about half-dozen times. One of those was also on a San Francisco street except it was so high it overlooked the Bay and there it was off to the left from the Bay Bridge (before it got the string of lights on the suspension). I think my camera at the time as an Instamatic, so did not even bother trying to get a shot.
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tasp
post Jul 22 2008, 03:00 AM
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I recall seeing Mercury at twilight ~20 years ago. It was setting towards a distant power line, and the rotation of the earth was easily apparent in the motion. Ingress and egress (behind the powerline) were instantaneous to my somewhat younger eye then.

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