Comments and questions about the
APOD on the main view screen.
-
APOD Robot
- Otto Posterman
- Posts: 5572
- Joined: Fri Dec 04, 2009 3:27 am
Post
by APOD Robot » Thu Oct 01, 2015 4:07 am
Eclipsed in Southern Skies
Explanation: This stunning panorama in southern skies was recorded on the colorful night of September 27/28 from Carnegie Las Campanas Observatory. A diffuse glow and dark rifts of the central Milky Way hang over domes of the twin 6.5 meter
Magellan telescopes. But most eye-catching is the deep red glow of the Moon. Immersed in Earth's shadow during the
much anticipated perigee-total-lunar eclipse, the Moon's surface reflects the light of sunsets and sunrises scattered and refracted into the planet's
cone-shaped umbra. Along with the dramatic hue of the eclipsed Moon, other colors of that night captured by the sensitive digital camera include the red and green shades of atmospheric airglow. Viewers can also spot the Andromeda Galaxy below the Moon, seen as a tiny smudge through the
reddish airglow and lights along the horizon. The Magellanic Clouds, satellite galaxies of the Milky Way, join in at the far left of
the full panorama frame.
[/b]
-
Ann
- 4725 Å
- Posts: 13806
- Joined: Sat May 29, 2010 5:33 am
Post
by Ann » Thu Oct 01, 2015 5:06 am
Beautiful image! It's great to see the small, reddened Moon sitting in a full panorama skyscape and appreciate how tiny the Moon really is.
As for the number of galaxies you can see in this image, you can acutually see M33 too, "on the other side of" Andromeda.
There is something about the orientation of this image that makes me disoriented. I would love an annotated version of this image, labelling the brighter stars. (Although I have, in fact, found Altair, Deneb and I think Vega, skirting the horizon. Oh, and Scorpius and Antares and Alpha and Beta Centauri, too.)
Ann
Color Commentator
-
Nitpicker
- Inverse Square
- Posts: 2692
- Joined: Fri Sep 20, 2013 2:39 am
- Location: S27 E153
Post
by Nitpicker » Thu Oct 01, 2015 7:52 am
Wow. It pays to click on the image and check out the full-res version. It is much wider.
-
Indigo_Sunrise
- Science Officer
- Posts: 440
- Joined: Fri Jul 15, 2005 1:40 pm
- Location: Md
Post
by Indigo_Sunrise » Thu Oct 01, 2015 10:40 am
Nitpicker wrote:Wow. It pays to click on the image and check out the full-res version. It is much wider.
x2.
I was just going to say that the full-res version is absolutely gorgeous!
Forget the box, just get outside.
-
Eric
- Ensign
- Posts: 14
- Joined: Wed Feb 20, 2013 12:33 pm
Post
by Eric » Thu Oct 01, 2015 12:31 pm
Great image, thanks! Typo note: Carngegie > Carnegie.
-
keeper of the faith
Post
by keeper of the faith » Thu Oct 01, 2015 1:10 pm
How did they stop Earth for this pretty shot?
-
Boomer12k
- :---[===] *
- Posts: 2691
- Joined: Sun Apr 22, 2007 12:07 am
Post
by Boomer12k » Thu Oct 01, 2015 1:56 pm
That is just and awesome image!!!
The Magellanic Clouds on the Left. The MW in the center, looking like a STORM, and then the Lunar Eclipse on the Right, and the awesome Twin Telescopes.
Excellent!!
:---[===] *
-
geckzilla
- Ocular Digitator
- Posts: 9180
- Joined: Wed Sep 12, 2007 12:42 pm
- Location: Modesto, CA
Post
by geckzilla » Thu Oct 01, 2015 2:25 pm
keeper of the faith wrote:How did they stop Earth for this pretty shot?
Yuri is quite magical.
Just call me "geck" because "zilla" is like a last name.
-
Cousin Ricky
- Science Officer
- Posts: 464
- Joined: Mon Aug 26, 2013 4:08 pm
- Location: St. Thomas, U.S. Virgin Islands (+18.3, -64.9)
Post
by Cousin Ricky » Thu Oct 01, 2015 2:32 pm
Why is the Moon darker than the glow surrounding it?
-
Chris Peterson
- Abominable Snowman
- Posts: 18573
- Joined: Wed Jan 31, 2007 11:13 pm
- Location: Guffey, Colorado, USA
Post
by Chris Peterson » Thu Oct 01, 2015 2:38 pm
keeper of the faith wrote:How did they stop Earth for this pretty shot? :roll:
This is a stitched panorama made from 15 separate, short duration images. With such wide angle shots, the duration was short enough that star trailing isn't easily detected. And I assume the sequence was taken in a sensible order, so there was very little motion between adjacent frames. I'm sure that if you plate solved the image, you'd see that the stars on one side are not where you'd expect them to be compared with stars on the other side, since over the entire sequence duration there would be a significant shift. But you'd never see that visually- it would have to be measured.
-
Chris Peterson
- Abominable Snowman
- Posts: 18573
- Joined: Wed Jan 31, 2007 11:13 pm
- Location: Guffey, Colorado, USA
Post
by Chris Peterson » Thu Oct 01, 2015 2:44 pm
Cousin Ricky wrote:Why is the Moon darker than the glow surrounding it?
That is odd, and visually unnatural, isn't it? It reminds me of a solar eclipse.
I was thinking about it, and I think it's because of the way the raw images were boosted to bring out the sky. Given the very dark sky at this location, the glow of the eclipsed Moon was actually quite a bit higher than the sky background (which isn't the case in more light polluted locations). So when the levels were adjusted to bring the background above black, the red Moon was so bright that you could see the surrounding glow from scatter in the optics (just as we always do with an overexposed, uneclipsed Moon in a night shot). There's nothing much to be done about that other than manually painting out the glow. But it does serve to nicely demonstrate the actual color of the Moon as captured by the camera. (I'm not sure, but it's possible that Yuri masked out the Moon itself when he boosted the background, to prevent it from being too bright. I can see how that might be necessary- I've done similar on eclipse photos in order to bring out background stars.)
-
geckzilla
- Ocular Digitator
- Posts: 9180
- Joined: Wed Sep 12, 2007 12:42 pm
- Location: Modesto, CA
Post
by geckzilla » Thu Oct 01, 2015 2:49 pm
It's the moon and the rest of the image having their dynamic ranges separated.
Just call me "geck" because "zilla" is like a last name.
-
WilliamAWelch1
Post
by WilliamAWelch1 » Thu Oct 01, 2015 4:35 pm
Why does the milky way appear curved? Isn't our galaxy flat?
-
Chris Peterson
- Abominable Snowman
- Posts: 18573
- Joined: Wed Jan 31, 2007 11:13 pm
- Location: Guffey, Colorado, USA
Post
by Chris Peterson » Thu Oct 01, 2015 5:00 pm
WilliamAWelch1 wrote:Why does the milky way appear curved? Isn't our galaxy flat?
It
is straight. But we're seeing a hemisphere projected onto a plane. That can't be done without introducing distortion. It's no different from ordinary maps, which usually show straight lines (such as latitude or longitude) as curved.
-
saturno2
- Commander
- Posts: 763
- Joined: Wed Jun 29, 2011 10:05 pm
Post
by saturno2 » Thu Oct 01, 2015 5:47 pm
Interesting image
-
neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Post
by neufer » Thu Oct 01, 2015 6:04 pm
Chris Peterson wrote:WilliamAWelch1 wrote:
Why does the milky way appear curved? Isn't our galaxy flat?
It
is straight. But we're seeing a hemisphere projected onto a plane. That can't be done without introducing distortion. It's no different from ordinary maps, which usually show straight lines (such as latitude or longitude) as curved.
Ordinary maps
projected onto a plane usually show latitude & longitude lines as straight.
Art Neuendorffer
-
Chris Peterson
- Abominable Snowman
- Posts: 18573
- Joined: Wed Jan 31, 2007 11:13 pm
- Location: Guffey, Colorado, USA
Post
by Chris Peterson » Thu Oct 01, 2015 6:13 pm
neufer wrote:Chris Peterson wrote:WilliamAWelch1 wrote:
Why does the milky way appear curved? Isn't our galaxy flat?
It
is straight. But we're seeing a hemisphere projected onto a plane. That can't be done without introducing distortion. It's no different from ordinary maps, which usually show straight lines (such as latitude or longitude) as curved.
Ordinary maps
projected onto a plane usually show latitude & longitude lines as straight.
I don't think so. The Mercator projection is the only common projection which does so, and it is not all that commonly used anymore.
-
neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Post
by neufer » Thu Oct 01, 2015 6:32 pm
Chris Peterson wrote:WilliamAWelch1 wrote:
Why does the milky way appear curved? Isn't our galaxy flat?
It
is straight. But we're seeing a hemisphere projected onto a plane. That can't be done without introducing distortion. It's no different from ordinary maps, which usually show straight lines (such as latitude or longitude) as curved.
Chris Peterson wrote:
I don't think so. The Mercator projection is the only common projection which does so,
and it is not all that commonly used anymore.
https://en.wikipedia.org/wiki/Web_Mercator wrote:
<<Web Mercator, Google Web Mercator, Spherical Mercator, WGS 84 Web Mercator or WGS 84/Pseudo-Mercator is a variation of the Mercator projection
and is the de facto standard for Web mapping applications. It rose to prominence when used in the first Google Maps in 2005. It is used by virtually all major online map providers, including Google Maps, Bing Maps, OpenStreetMap, Mapquest, Mapbox, and many others.
Web Mercator shares some of the same properties of the standard Mercator projection: north is up everywhere, meridians are equally spaced vertical lines, but areas near the poles are greatly exaggerated.
Unlike the ellipsoidal Mercator and spherical Mercator, the Web Mercator is not quite conformal due to its use of ellipsoidal datum geographical coordinates against a spherical projection.
Rhumb lines are not straight lines. The benefit is that the spherical form is much simpler to calculate, saving many computing cycles.>>
Art Neuendorffer
-
ThePiper
- Ensign
- Posts: 51
- Joined: Wed Mar 16, 2011 10:16 am
- Location: Swiss
Post
by ThePiper » Thu Oct 01, 2015 6:34 pm
Ann wrote:Beautiful image! It's great to see the small, reddened Moon sitting in a full panorama skyscape and appreciate how tiny the Moon really is.
Yes, true.
But it's a wrong world: The fiery Moon vs the pale Andromeda Galaxy - a grain of dust vs. a giant cosmic vortex! Images
always lie.
-
neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Post
by neufer » Thu Oct 01, 2015 6:57 pm
ThePiper wrote:
Images
always lie.
Only when
projected onto a plane
Art Neuendorffer
-
BMAONE23
- Commentator Model 1.23
- Posts: 4076
- Joined: Wed Feb 23, 2005 6:55 pm
- Location: California
Post
by BMAONE23 » Thu Oct 01, 2015 7:21 pm
And outside the Sphere of Influence
-
gvann
Post
by gvann » Fri Oct 02, 2015 3:13 am
neufer wrote:Chris Peterson wrote:WilliamAWelch1 wrote:
Why does the milky way appear curved? Isn't our galaxy flat?
It
is straight. But we're seeing a hemisphere projected onto a plane. That can't be done without introducing distortion. It's no different from ordinary maps, which usually show straight lines (such as latitude or longitude) as curved.
Chris Peterson wrote:
I don't think so. The Mercator projection is the only common projection which does so,
and it is not all that commonly used anymore.
https://en.wikipedia.org/wiki/Web_Mercator wrote:
<<Web Mercator, Google Web Mercator, Spherical Mercator, WGS 84 Web Mercator or WGS 84/Pseudo-Mercator is a variation of the Mercator projection
and is the de facto standard for Web mapping applications. It rose to prominence when used in the first Google Maps in 2005. It is used by virtually all major online map providers, including Google Maps, Bing Maps, OpenStreetMap, Mapquest, Mapbox, and many others.
Web Mercator shares some of the same properties of the standard Mercator projection: north is up everywhere, meridians are equally spaced vertical lines, but areas near the poles are greatly exaggerated.
Unlike the ellipsoidal Mercator and spherical Mercator, the Web Mercator is not quite conformal due to its use of ellipsoidal datum geographical coordinates against a spherical projection.
Rhumb lines are not straight lines. The benefit is that the spherical form is much simpler to calculate, saving many computing cycles.>>
Even in a Mercator projection, straight lines other than N-S and E-W do not appear straight.