APOD: Mercury on the Horizon (2013 Feb 19)

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Expand view Topic review: APOD: Mercury on the Horizon (2013 Feb 19)

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

by alter-ego » Tue Feb 26, 2013 5:47 am

MargaritaMc wrote:Gosh. That is SO skilful, alter-ego. And SO helpful.
:clap: :clap: :clap: :clap:
Thank you very much, MargritaMc, I'm happy you and others found these graphics helpful. I really enjoy and appreciate having the APOD platform to share these things.

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

by MargaritaMc » Mon Feb 25, 2013 9:09 am

Gosh. That is SO skilful, alter-ego. And SO helpful.
:clap: :clap: :clap: :clap:

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

by alter-ego » Mon Feb 25, 2013 1:06 am

Anthony Barreiro wrote: That is really helpful. I've been looking at this beautiful apod repeatedly since yesterday, and I'm seeing the motion of Mercury passing between the Earth and Sun. You can't see this movement at a point in time, and even building up a mental picture through repeated observations is much less vivid and immediate than this image. Thanks imagers!
I thought I'd take this one step farther. The pictures in my original post were modified to include a snapshot of of Mercury's orbit (red elipse) on Feb 14. It's clear the deviation from this orbit is due to Earth's movement over 25 days and the changing perspective of Mercury's tilted orbit wrt Earth's orbital plane. So I've further separated out the Earth / Mercury relative motions in the GIF below. Our evolving perspective of Mercury's orbit (wrt the Sun) is visible as well as Mercury's position. I think you might like this.
 
Image
Click to view full size image 1 or image 2

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

by Anthony Barreiro » Wed Feb 20, 2013 8:10 pm

alter-ego wrote: I've created two composites simulating the Mercury composite today. The location is Spain, and date range is Feb 1 to Feb 25, 2000. The green region is a fake semitransparent ground (W = West in the base image). The base image is for a fixed horizon, and you can see the motion of the Sun along a line 10° below the horizon. The hover image is the same date range, but the sun is fixed, also at 10°below the horizon (i.e. horizon moves). I've left off the "W" in this image. You can see that the bulk of Mercury's motion along the horizon is do to the Sun's relative motion. The hover image does show that a little less than half of the planet's motion along the horizon is relative to the Sun. I believe this is a reasonable representation.
That is really helpful. I've been looking at this beautiful apod repeatedly since yesterday, and I'm seeing the motion of Mercury passing between the Earth and Sun. You can't see this movement at a point in time, and even building up a mental picture through repeated observations is much less vivid and immediate than this image. Thanks imagers!

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

by MargaritaMc » Wed Feb 20, 2013 11:46 am

BRILLIANT! Thanks so much, alter-ego. It clarifies things for me as well.
Margarita

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

by alter-ego » Wed Feb 20, 2013 7:17 am

Chris Peterson wrote:
DavidM wrote:Do the nightly positions of Mercury take into account the gradual westward movement of the Sun at sunset? In other words, are we seeing positions of Mercury relative to the mountain backdrop, or relative to the setting sun?
I'd say, to a first approximation, the vertical movement is relative to the Sun, but the horizontal is relative to the horizon. The time of each shot seems to have been determined by fixing the distance of the Sun below the horizon, so the image reflects the drift in sunset position over the time series.
I've created two composites simulating the Mercury composite today. The location is Spain, and date range is Feb 1 to Feb 25, 2000. The green region is a fake semitransparent ground (W = West in the base image). The base image is for a fixed horizon, and you can see the motion of the Sun along a line 10° below the horizon. The hover image is the same date range, but the sun is fixed, also at 10°below the horizon (i.e. horizon moves). I've left off the "W" in this image. You can see that the bulk of Mercury's motion along the horizon is do to the Sun's relative motion. The hover image does show that a little less than half of the planet's motion along the horizon is relative to the Sun. I believe this is a reasonable representation.
Click to view full size image 1 or image 2

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

by Chris Peterson » Wed Feb 20, 2013 1:08 am

DavidM wrote:Do the nightly positions of Mercury take into account the gradual westward movement of the Sun at sunset? In other words, are we seeing positions of Mercury relative to the mountain backdrop, or relative to the setting sun?
I'd say, to a first approximation, the vertical movement is relative to the Sun, but the horizontal is relative to the horizon. The time of each shot seems to have been determined by fixing the distance of the Sun below the horizon, so the image reflects the drift in sunset position over the time series.

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

by DavidM » Wed Feb 20, 2013 12:59 am

Do the nightly positions of Mercury take into account the gradual westward movement of the Sun at sunset? In other words, are we seeing positions of Mercury relative to the mountain backdrop, or relative to the setting sun?

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

by Anthony Barreiro » Tue Feb 19, 2013 10:50 pm

Boomer12k wrote:... .
Here is a photo of the east end of our street, from my driveway, where I do my Astronomy. Poor as it is. The red dot is where Mercury was in my shot, maybe a tad lower. (May not be exact. But you get the idea.) And the dot is over-sized for emphasis. The Yellow dot is where I saw it the first time through my scope. ... .

I also do not have the luxury of taking my 100 pound scope and dolly in my 240 Z, out to a deserted location. Not happening. So, you can see I don't live at the top of Mauna Kea, and Mt. Palomar was taken.

...

Clear Skies, and unobstructed views, everyone!!! Space telescopes are the BEST!!!!

:---[===] *
We all do what we can with our equipment, location, and sky conditions. I would much rather see what I can from my light-polluted back yard with its ridiculously obstructed horizon than sit around inside complaining that you can't see anything in the city. Trips to dark sky locations are a real treat.

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

by Boomer12k » Tue Feb 19, 2013 9:58 pm

Anthony Barreiro wrote:
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.
--------------------------------------------------------------------------------------
SIR!!!!
Thank you for your input and suggestions. Much Appreciated. I value your expert advise, and admire your work!!!!
I do not have the luxury of an unobstructed view. Even up on the hill, we have a park with tall trees. No way viewing of ANYTHING, but straight up is happening. On my street in the Summer, leaves block most everything. I was lucky to see it at all. Only because it reached just over the top of the trees. Dawn was really already happening. I could well see everything around me. Software is little help, in that it does not show my particular tree line. So, even knowing the positions relative to other stars or planets is of little help. Could not see other stars for reference. I have bad eyesight to begin with, and against the dawn could not see it. Even with my scope ON IT, could not find it with my Binocs. The other time I saw Mercury was just through the branches in Winter, so no leaves. Man what a sight. Whitish-fiery red, it was AWESOME, I was "struck". Wish I had, had my camera back then.
So, it maybe overly stated to be difficult...if you have the unobstructed view, and are relatively experienced with Mercury. Which I don't have, and which I was not. So, in my particular case, "nearly impossible without a computerized scope", is quite accurate. From my situation.
Here is a photo of the east end of our street, from my driveway, where I do my Astronomy. Poor as it is. The red dot is where Mercury was in my shot, maybe a tad lower. (May not be exact. But you get the idea.) And the dot is over-sized for emphasis. The Yellow dot is where I saw it the first time through my scope. There may have been an evening time, I forgot about in the West, but it was like the yellow dot, just barely, through some branches, in Winter. I have a RELATIVELY unobstructed view to the SE, SW, NW, NE, and E above the treeline. I have a HUGE Oak tree that blocks the North almost entirely, across the street, I can just see Polaris. The south is blocked by the house and trees somewhat, the west is like the east, with a higher treeline. So, I hope you can appreciate my predicament. I PRAY for a HUGE WIND STORM to take down that Oak Tree!!!!!!! Or make it a law that the horizon MUST BE CLEARED!!!! But until then, you can see what I deal with. Lucky to see anything. M16 is South, I can get it just before it goes into the trees!!!
I also do not have the luxury of taking my 100 pound scope and dolly in my 240 Z, out to a deserted location. Not happening. So, you can see I don't live at the top of Mauna Kea, and Mt. Palomar was taken.

I am thinking of going back to a smaller computerized refractor....hmmmm...got some tax money coming back soon....hmmmmmmm....

I had a friend bring back my old Jason, I gave him, the camera would not fit the eyepiece holder.

Clear Skies, and unobstructed views, everyone!!! Space telescopes are the BEST!!!!

:---[===] *
Attachments
My view to the east.
My view to the east.

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

by Jim Herbert » Tue Feb 19, 2013 8:50 pm

Joe, thanks again for this:

"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." There were some assumptions in my ideas that this has corrected.

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

by 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.

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

by 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.

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

by 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.

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

by 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. >>

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

by 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".

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

by 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.

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

by 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. :?

Margarita

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

by 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.

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

by 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

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

by neufer » Tue Feb 19, 2013 5:58 pm

http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_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.>>

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

by 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.

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

by 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.

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

by 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.

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

by 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.

Joe

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