APOD: Cities at Night (2016 Mar 05)

Comments and questions about the APOD on the main view screen.
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APOD: Cities at Night (2016 Mar 05)

Post by APOD Robot » Sat Mar 05, 2016 5:07 am

Image Cities at Night

Explanation: Looking toward the south from an altitude of 400 kilometers, this stunning snapshot from orbit finds bright lights of Tokyo and cities across central and southern Japan, planet Earth shining upward through broken clouds. The spacefaring perspective was captured last July by astronaut Scott Kelly during his stay on board the International Space Station. Thin stripes of airglow follow the curve of the planet's dark limb, while beyond lie stars of the constellation Centaurus and the southern sky. Their solar panels extended, a docked Soyuz (bottom) and Progress spacecraft are posed in the foreground. Kelly returned to planet Earth this week after his one-year mission in space.

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Cousin Ricky » Sat Mar 05, 2016 2:33 pm

I'm curious about the white balance of this photo&mdash;or, why do the spacecraft look blue?

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Re: APOD: Cities at Night (2016 Mar 05)

Post by rstevenson » Sat Mar 05, 2016 3:03 pm

Cousin Ricky wrote:I'm curious about the white balance of this photo&mdash;or, why do the spacecraft look blue?
As downloaded, the image seems not to have any bluish cast overall. I checked with a digital colour meter, and the black areas are close to 0 (zero) in R, G, and B channels, and the whitest area is very close to 254 in all three channels. So I'd have to say that the blueish parts of the ISS and its visitors must have some blue light shining on them.

Rob

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Ludo » Sat Mar 05, 2016 3:27 pm

I'm curious about the black patch inside Tokyo.. Is that just water or some sort of blackout?

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Ludo » Sat Mar 05, 2016 3:29 pm

Never mind. It's water. It just seemed too geometrical for it to be geographical. Should've checked before asking.

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Coil_Smoke » Sat Mar 05, 2016 6:15 pm

rstevenson wrote:
Cousin Ricky wrote:I'm curious about the white balance of this photo&mdash;or, why do the spacecraft look blue?
As downloaded, the image seems not to have any bluish cast overall. I checked with a digital colour meter, and the black areas are close to 0 (zero) in R, G, and B channels, and the whitest area is very close to 254 in all three channels. So I'd have to say that the blueish parts of the ISS and its visitors must have some blue light shining on them.

Rob
Could the our Moon be the source of the light ? I see no readily available date of the photo and wonder about the Lunar phase and position :?:

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Re: APOD: Cities at Night (2016 Mar 05)

Post by rstevenson » Sat Mar 05, 2016 6:35 pm

Coil_Smoke wrote:
rstevenson wrote:
Cousin Ricky wrote:I'm curious about the white balance of this photo&mdash;or, why do the spacecraft look blue?
As downloaded, the image seems not to have any bluish cast overall. I checked with a digital colour meter, and the black areas are close to 0 (zero) in R, G, and B channels, and the whitest area is very close to 254 in all three channels. So I'd have to say that the blueish parts of the ISS and its visitors must have some blue light shining on them.
Could the our Moon be the source of the light ? I see no readily available date of the photo and wonder about the Lunar phase and position :?:
Well, the Moon simply reflects sunlight, so that shouldn't make anything blue either. There must have been light spilling out of the ISS windows, or otherwise coming from the ISS -- maybe deliberately in order to make the photo more interesting. Photographers have been known to light their subjects in interesting ways before.

Rob

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Chris Peterson » Sat Mar 05, 2016 6:36 pm

Coil_Smoke wrote:Could the our Moon be the source of the light ? I see no readily available date of the photo and wonder about the Lunar phase and position :?:
The image was made on 25 July 2015 at UT 13:43. The view is to the southwest, almost directly towards the 74% moon (out of the field at the top). At this time, ISS was only just in the night, with the Sun lighting the northern horizon behind it- almost certainly the source of the blue light. (And the Moon is white.)
tokyo.jpg
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Re: APOD: Cities at Night (2016 Mar 05)

Post by Coil_Smoke » Sat Mar 05, 2016 7:10 pm

Thanks for the great and totally detailed answers...

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Catalina » Sun Mar 06, 2016 12:49 am

Has the appearance of city lights been enhanced to a degree, or is the land area of Japan actually as congested by human occupation as it appears in this image?

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Beyond » Sun Mar 06, 2016 1:39 am

Coil_Smoke wrote:Thanks for the great and totally detailed answers...

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Re: APOD: Cities at Night (2016 Mar 05)

Post by geckzilla » Sun Mar 06, 2016 2:28 am

Catalina wrote:Has the appearance of city lights been enhanced to a degree, or is the land area of Japan actually as congested by human occupation as it appears in this image?
Humans put a lot of light into the atmosphere. That said, a camera will see things differently than a human eye.
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Re: APOD: Cities at Night (2016 Mar 05)

Post by Boomer12k » Sun Mar 06, 2016 4:26 am

Ah....Shinjuku in the Spring.... Sakura....

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Re: APOD: Cities at Night (2016 Mar 05)

Post by Cousin Ricky » Sun Mar 06, 2016 5:37 am

Chris Peterson wrote:The image was made on 25 July 2015 at UT 13:43. The view is to the southwest, almost directly towards the 74% moon (out of the field at the top). At this time, ISS was only just in the night, with the Sun lighting the northern horizon behind it- almost certainly the source of the blue light. (And the Moon is white.)
tokyo.jpg
I'm going with your explanation. I just noticed that the lower right corner of Soyuz is lit with a warmer white light. This would be consistent with the Moon's position.

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Re: APOD: Cities at Night (2016 Mar 05)

Post by alter-ego » Mon Mar 07, 2016 5:01 am

Cousin Ricky wrote:
Chris Peterson wrote:The image was made on 25 July 2015 at UT 13:43. The view is to the southwest, almost directly towards the 74% moon (out of the field at the top). At this time, ISS was only just in the night, with the Sun lighting the northern horizon behind it- almost certainly the source of the blue light. (And the Moon is white.)
I'm going with your explanation. I just noticed that the lower right corner of Soyuz is lit with a warmer white light. This would be consistent with the Moon's position.
To add some detail, the Moon and Sun positions wrt the ISS are indicated below.
Tokyo from ISS - Sun & Moon Locations.JPG
Below is a frame from a time-lapse video (2011 APOD) showing what Earth's limb looks like when the Sun-lit from 13° below the limb. Judging by star visibility and blue ISS illumination, this is probably is quite representative of todays APOD.
Sun 13° Below Limb - APOD 27 Sep 2011.JPG
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Re: APOD: Cities at Night (2016 Mar 05)

Post by neufer » Wed Mar 09, 2016 3:31 pm

http://earthobservatory.nasa.gov/IOTD/view.php?id=87646 wrote:

<<On March 6, 2016, news and social media was buzzing with spectacular photographs of the northern lights (aurora borealis) painting skies across the United Kingdom with brilliant shades of green and pink.

The event was impressive from above as well. Using the day-night band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS), the Suomi NPP satellite acquired this view of the aurora borealis on March 7, 2016. Auroras appear as white streaks over Iceland, the North Atlantic, and Norway. The DNB sensor detects dim light signals such as airglow, gas flares, city lights, and reflected moonlight. In the image above, the sensor detected the visible light emissions that occur when energetic particles rain down from Earth’s magnetosphere into the gases of the upper atmosphere.

It is not often that the northern lights are visible south of Scotland and Northern Ireland, but a geomagnetic storm colored night skies over a much wider swath of the country. The storm reached a G3 or “severe” level on NOAA’s geomagnetic storm scale, according to the Space Weather Prediction Center. On March 7, the Kp index—a metric for global geomagnetic storm activity—rose as high as 7 on a scale that goes to 9.

The brilliant colors of the aurora are provoked by activity the Sun: Solar energy and particles speed toward Earth in a steady stream called the solar wind, or they rush out in massive eruptions known as coronal mass ejections. (CMEs). These storms from the Sun disturb geospace (the space around Earth) and energize particles already trapped in the magentosphere and radiation belts. Electrons then race down Earth’s magnetic field lines and crash into the gases at high altitudes of the atmosphere. Oxygen gives off a green color when excited; nitrogen produces blue or red colors.>>
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