APOD: Mercury on the Horizon (2013 Feb 19)

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APOD: Mercury on the Horizon (2013 Feb 19)

Postby APOD Robot » Tue Feb 19, 2013 5:06 am

Image Mercury on the Horizon

Explanation: Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun, it never wanders far from the Sun in Earth's sky. If trailing the Sun, Mercury will be visible low on the horizon for only a short while after sunset. If leading the Sun, Mercury will be visible only shortly before sunrise. So at certain times of the year an informed skygazer with a little determination can usually pick Mercury out from a site with an unobscured horizon. Above, a lot of determination has been combined with a little digital manipulation to show Mercury's successive positions during March of 2000. Each picture was taken from the same location in Spain when the Sun itself was 10 degrees below the horizon and superposed on the single most photogenic sunset. Currently, Mercury is visible in the western sky after sunset, but will disappear in the Sun's glare after a few days.

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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby henrystar » Tue Feb 19, 2013 10:27 am

An oldie but goodie.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby saturno2 » Tue Feb 19, 2013 11:10 am

Good image, good contrast.
Mercury in the sky, in year 2000
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Ann » Tue Feb 19, 2013 11:24 am

That's a stunning image, lovely colors. The "arc of Mercury" looks graceful and beautiful against the sky.

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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Boomer12k » Tue Feb 19, 2013 11:52 am

Or, if you have a computerized telescope you can get a shot of Mercury even through the branches of the trees at the end of the street! If you're LUCKY!

Shot was early morning, just before sunrise. Actually this one was above the trees, barely. This was the SECOND time I had ever SEEN MERCURY, both were with my 10" Meade. A bright, fiery red dot. Even knowing where it was, I could not find it with my 10 power binoculars. Very difficult even with computer controls, as it is not totally centered when the scope finds it. So, you have to hunt a little bit. But worth the wait... :D

Click on the picture, then click again for close up, and you can see the PHASE. Picture should actually be flipped horizontally for proper view, the sun was low to the left. It was early August 2012. My focus also isn't very good, and the atmosphere interferes too.

The picture looks dark, but the sky was actually early dawn.

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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby MargaritaMc » Tue Feb 19, 2013 12:06 pm

I sheepishly confess to a feeling of relief, after all the excitement of the last few days, to open my browser to this blissfully calm and beautiful Apod. I've never yet managed to see Mercury and hadn't realised what a very marked arc it makes over this period of ¿19? days. (That is how many images of Mercury I could count, but my small screen may not show all that are there.)
Apod text writes Each picture was taken from the same location in Spain.

Because I am pedantic, I discovered that this location was Figures, in Catalonia - the birthplace of Salvador Dali.
http://en.wikipedia.org/wiki/Figueres

M
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby MargaritaMc » Tue Feb 19, 2013 12:13 pm

Boomer12k » Tue Feb 19, 2013 11:52 am

Or, if you have a computerized telescope you can get a shot of Mercury even through the branches of the trees at the end of the street! If you're LUCKY!.


That is most impressive, Boomer. Yes, I can actually see the phase of Mercury in your picture.

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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby NMN » Tue Feb 19, 2013 1:02 pm

Looks a lot like a game of the old classic, Scorched Earth :)
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby fausto.lubatti » Tue Feb 19, 2013 1:35 pm

Beautiful colors and an original idea that shows the path of the planet.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby emc » Tue Feb 19, 2013 2:13 pm

Well done beautiful scene... with Mercury’s rise and fall over time… remindful of relationships long past.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby MadMan » Tue Feb 19, 2013 2:14 pm

I saw Mercury once. The previous night, Jack Horkheimer, "Star Hustler" had shown a diagram of the relative positions of the moon, Venus, and Mercury just after sunset. I went outside and there they were!
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Joe Stieber » Tue Feb 19, 2013 2:50 pm

I think the difficulty in finding Mercury is greatly overstated, to the point that a lot of folks don’t even try. I had been seeing it on an irregular basis for many years, but after spotting it in January 2011, I decided to attempt seeing it at every elongation that year (seven of them) and succeeded. I continued through 2012 (six more elongations), and again during the current elongation this month (February 2013). That makes it fourteen (14) elongations in a row.

This month, I’ve seen it on nine different evenings. On the majority of the nights this month, it’s been a relatively easy object for the unaided eye (after locating it with binoculars in most cases). I’ve also been prompted by an article at Sky & Telescope which suggested following Mercury with a scope through this fine elongation to watch the changing phase. Last week, using my 80 mm refractor, I could see the gibbous shape (less than a full disc, but more than half illuminated), and yesterday (February 18th), it was a crescent (less than half illuminated). I hope to see it in the scope a few more times this month as the crescent narrows and the diameter increases as it approaches inferior conjunction (March 4th).

The ultimate point is that Mercury isn’t really hard to see if one is determined to do so! It just takes a little preparation, and in this day and age of planetarium programs, online information and mobile apps, it isn't that hard to prepare.

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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Chris Peterson » Tue Feb 19, 2013 3:15 pm

Joe Stieber wrote:I think the difficulty in finding Mercury is greatly overstated, to the point that a lot of folks don’t even try.

I agree, you've hit the nail on the head. Mercury is easy to see. I can often make it out, even with my poor horizons. It simply requires knowing when and where to look. The only thing that makes it a bit tricky is the narrow time window, both in terms of the evening or morning minutes and the few days when it is far enough from the Sun. But for anybody interested in looking, it really doesn't take much effort or skill to see Mercury.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby jim herbert » Tue Feb 19, 2013 4:52 pm

I'm a long-time APOD fan, but no astronomer, so please bear with an inexpert question:

Is the time sequence from left to right, or the reverse? I am assuming the former.

Here's another, more fun question: Where in the path is Mercury moving directly, and where is it moving retrograde? Remember that the writer is not an astronomer.

Thanks in advance, and I can only say: what a splendid picture.

If the conditions are right, I agree that it's not hard to see this elusive planet. It's also a thrill when we succeed in seeing it the first time.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby LocalColor » Tue Feb 19, 2013 5:21 pm

Kudos to the photographer for patience and persistence! A very lovely photo and the luck to have clear skies.

We are in a narrow valley, so the mountains do not allow us to see Mercury from here.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby neufer » Tue Feb 19, 2013 5:58 pm

http://messenger.jhuapl.edu/gallery/sci ... ge_id=1095 wrote:
Click to play embedded YouTube video.

<<This colorful view of Mercury was produced by using images from the color base map imaging campaign during MESSENGER's primary mission. These colors are not what Mercury would look like to the human eye, but rather the colors enhance the chemical, mineralogical, and physical differences between the rocks that make up Mercury's surface.

Young crater rays, extending radially from fresh impact craters, appear light blue or white. Medium- and dark-blue areas are a geologic unit of Mercury's crust known as the "low-reflectance material", thought to be rich in a dark, opaque mineral. Tan areas are plains formed by eruption of highly fluid lavas. The crater whose rays stretch across the planet is Hokusai. The giant Caloris basin is the large circular tan feature.>>
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Joe Stieber » Tue Feb 19, 2013 6:38 pm

jim herbert wrote:I'm a long-time APOD fan, but no astronomer, so please bear with an inexpert question: Is the time sequence from left to right, or the reverse? I am assuming the former. Here's another, more fun question: Where in the path is Mercury moving directly, and where is it moving retrograde? Remember that the writer is not an astronomer.

The accompanying text says this APOD shows Mercury’s successive positions during March of 2000. Actually, the picture was originally the APOD on March 20, 2000, and Mercury’s Greatest Western Elongation that month was on March 28, 2000, with Venus nearby in the morning sky (and bright Venus is absent here), so it’s not plausible that it was taken in March 2000.

There was a Greatest Eastern Elongation (in the evening sky) on February 14, 2000. Since the ecliptic is favorably steep in the west after sunset in February (as it is now during February 2013), there’s a good chance the individual images were taken in February 2000.

If it is indeed an evening picture, then Mercury would be in direct motion starting in the lower-left as it draws away from superior conjunction on January 5, 2000. It was stationary at Greatest Eastern Elongation on February 14, 2000, at the top of the hump, then in retrograde motion on the right of the right-hand side of the hump as it heads back towards the sun and inferior conjunction on March 1, 2000.

Notice that the brightness of Mercury fades as it moves from left to right, even though it's moving a bit closer to earth. Unlike Venus, Mercury is brightest near superior conjunction when it's "full," then dims from a decreasing phase as it swings around towards inferior conjunction. It brightens again as it moves from inferior to superior conjunction.

In any case, a beautiful and fascinating picture!

Joe
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby BDanielMayfield » Tue Feb 19, 2013 7:13 pm

jim herbert wrote:Where in the path is Mercury moving directly, and where is it moving retrograde? Remember that the writer is not an astronomer.

I'm not an astronomer either Jim, but I don't think that planets interior to the earth (Mercury and Venus) ever move in a retrograde direction because they move faster than than the earth in their orbits around the sun. Exterior planets (Mars and beyond) preform apparent retrograde loops when the earth passes these slower movers.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby MargaritaMc » Tue Feb 19, 2013 7:14 pm

Joe Stieber wrote..If it is indeed an evening picture, then Mercury would be in direct motion starting in the lower-left as it draws away from superior conjunction on January 5, 2000. It was stationary at Greatest Eastern Elongation on February 14, 2000, at the top of the hump, then in retrograde motion on the right of the right-hand side of the hump as it heads back towards the sun and inferior conjunction on March 1, 2000.


I have severe difficulty in picturing how what is happening, as described by Joe above, relates to what we see in the Apod. I have a kind of perceptional glitch, I think. :?

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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Chris Peterson » Tue Feb 19, 2013 7:23 pm

MargaritaMc wrote:I have severe difficulty in picturing how what is happening, as described by Joe above, relates to what we see in the Apod. I have a kind of perceptional glitch, I think. :?

It's complicated in several ways (besides the fact that the date doesn't seem to work). The height above the horizon is essentially the elongation- how far away Mercury appears from the Sun. That's because the images are timed such that the Sun is always the same distance below the horizon. But the lateral movement is primarily caused by the northward drift of the Sun from day to day, not the movement of Mercury. There are several different motions superimposed here.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby ai.niwa » Tue Feb 19, 2013 7:26 pm

I think that "show Mercury's successive positions during February of 2000" is correct, not "during March of 2000".
Because Mercury must disappeared in the Sun's glare during March of 2000 like this year according to the astronomical softwares and in the first appearance of this article on 2000 March 20 it was described as“show Mercury's successive positions during the middle of last month".
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby neufer » Tue Feb 19, 2013 7:54 pm

BDanielMayfield wrote:
jim herbert wrote:
Where in the path is Mercury moving directly, and where is it moving retrograde? Remember that the writer is not an astronomer.

I'm not an astronomer either Jim, but I don't think that planets interior to the earth (Mercury and Venus) ever move in a retrograde direction because they move faster than than the earth in their orbits around the sun. Exterior planets (Mars and beyond) preform apparent retrograde loops when the earth passes these slower movers.

I'm not an astronomer either but I once played one in grad school.

Mercury and Venus move in a retrograde direction (i.e., westward vis-a-vis the Zodiac) during transits & inferior conjunctions as well as most of the rest of the time during which they are closer to the Earth than is the Sun.

http://apod.nasa.gov/apod/ap120527.html
http://apod.nasa.gov/apod/ap120620.html
http://apod.nasa.gov/apod/ap120920.html

http://en.wikipedia.org/wiki/Apparent_retrograde_motion wrote:
<<Though [the Sun, Moon,] all stars and planets appear to move from east to west on a nightly basis in response to the rotation of Earth, [the Sun, Moon, and] planets generally drift slowly eastward relative to the stars. This motion is normal and so is considered direct motion. However, since Earth completes its orbit in a shorter period of time than the planets outside its orbit, it periodically overtakes them, like a faster car on a multi-lane highway. When this occurs, the planet being passed will first appear to stop its eastward drift, and then drift back toward the west. Then, as Earth swings past the planet in its orbit, it appears to resume its normal motion west to east.

Inner planets Venus and Mercury appear to move in retrograde [vis-a-vis the background stars] in a similar mechanism, but as they can never be in opposition to the Sun as seen from Earth, their retrograde cycles are tied to their lower conjunctions with the Sun. >>
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Jim Herbert » Tue Feb 19, 2013 8:06 pm

Joe, thanks very much for that information. All of it!

"Mercury is brightest near superior conjunction when it's "full," then dims from a decreasing phase as it swings around towards inferior conjunction." - That's a revelation for me. Fascinating. I would have thought it analogous to the case of Venus. Probably has something to do with the difference in respective albedos, and also because Venus is so much closer when inferior conjunction is near.

BDanielMayfield, thanks. Retrograde motion is something more complex than what I had in mind, apparently, as Chris points out. Maybe it's a simpler proposition in the case of the planets external to Earth. However, I would think that Mercury goes retrograde for some time during its approach to superior conjunction and beyond, when it passes behind the Sun. I'm thinking of its absolute position in the sky relative to an earthbound observer.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Joe Stieber » Tue Feb 19, 2013 8:25 pm

Joe Stieber wrote:It was stationary at Greatest Eastern Elongation on February 14, 2000.

Mea culpa! I scribbled too quickly. Mercury would have been stationary about February 20, 2000 (not the 14th). Mercury is stationary some days after Greatest Eastern Elongation because even though the apparent spacing between Mercury and the sun begins decreasing after greatest elongation, the Sun+Mercury system is initially moving eastward against the background stars at a greater rate than Mercury is moving backs towards the sun. The net result is Mercury moving eastward too. On the 20th, Mercury's westward motion towards the sun finally exceeds the sun's continuous eastward movement.

Direct (eastward) and retrograde (westward) motion are defined by the planet's movement relative to the background stars, not to be confused with the retrograde loops of the exterior planets.
Last edited by Joe Stieber on Tue Feb 19, 2013 11:13 pm, edited 1 time in total.
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Re: APOD: Mercury on the Horizon (2013 Feb 19)

Postby Anthony Barreiro » Tue Feb 19, 2013 8:31 pm

Boomer12k wrote:Or, if you have a computerized telescope you can get a shot of Mercury even through the branches of the trees at the end of the street! If you're LUCKY!

Shot was early morning, just before sunrise. Actually this one was above the trees, barely. This was the SECOND time I had ever SEEN MERCURY, both were with my 10" Meade. A bright, fiery red dot. Even knowing where it was, I could not find it with my 10 power binoculars. Very difficult even with computer controls, as it is not totally centered when the scope finds it. So, you have to hunt a little bit. But worth the wait... :D

Click on the picture, then click again for close up, and you can see the PHASE. Picture should actually be flipped horizontally for proper view, the sun was low to the left. It was early August 2012. My focus also isn't very good, and the atmosphere interferes too.

The picture looks dark, but the sky was actually early dawn.

:---[===] *


Boomer, you're probably going to have better luck finding Mercury with a computerized scope during dawn apparitions than evening apparitions. My go-to scope needs two bright stars for alignment before it can find planets. In the evening Mercury will be setting and low toward the horizon by the time the stars come out, whereas in the morning if you get up before dawn you can align your scope and wait for Mercury to rise.

As Joe and Chris said, I find it pretty easy to see Mercury with binoculars and naked-eye during decent apparitions (although unlike Joe I don't even try to see poor apparitions). The most important thing is to find someplace with an unobstructed horizon -- my local hilltop park works well. And you need to look at the right time. For evening apparitions get out around sunset and start scanning, you'll see Mercury within 30 minutes. In the morning start looking around Mercury's predicted rising time, and again you should be able to see Mercury within 30 minutes or so. In either the morning or the evening you'll get the best view when Mercury is highest in the sky: as soon as possible in the evening, and as late as possible in the morning.

Given the amount of atmospheric distortion during Mercury's low appearances, I find I get a steadier view through a smaller aperture telescope. In my 70 mm refractor at 50x magnification, when the atmosphere is relatively steady I can see Mercury's phase.
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