Starship Asterisk*

Station and Shuttle Transit the Sun

Explanation: That's no sunspot. On the upper right of the above image of the Sun, the dark patches are actually the International Space Station (ISS) and the Space Shuttle Atlantis on mission STS-132. In the past, many skygazers have spotted the space station and space shuttles as bright stars gliding through twilight skies, still glinting in the sunlight while orbiting about 350 kilometers above the Earth's surface. But here, astrophotographer Thierry Lagault accurately computed the occurrence of a rarer opportunity to record the spacefaring combination moving quickly in silhouette across the solar disk. He snapped the above picture on last Sunday on May 16, about 50 minutes before the shuttle docked with the space station. Atlantis was recently launched to the ISS for its last mission before being retired.

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Amazing photo! Nice clear photo of the ISS!

The moon may be made out of cheese, but THAT picture of the sun looks just like a cornmeal cookie - with a couple of little bugs on it.
Yum-yum-yum agh! pa-too

http://galliform.bhs.mq.edu.au/~phil/_G ... 0fruit.jpg


Neufer--for you.

As I have said: Good choice! I think it's amazing how sharp you can take a photo with the sun as background! WOW!

Why is the background black?

query wrote:Why is the background black?

Perhaps I did not get your question... but usually there is no stronger light source behind or beside the sun that could cause a lighter background. Hence it is black because you also don't see stars due to the filter(s) used to prevent the eyes or the camera of damages...

Hofi wrote:

query wrote:Why is the background black?

Perhaps I did not get your question... but usually there is no stronger light source behind or beside the sun that could cause a lighter background. Hence it is black because you also don't see stars due to the filter(s) used to prevent the eyes or the camera of damages...

besides, such short exposure won't let the camera to catch Stars!

Amir wrote:besides, such short exposure won't let the camera to catch Stars!

How long do you usuallly exposure the sun?

Hofi wrote:How long do you usually exposure the sun?

depends on many factors like aperture, ISO, etc. you should ask experts, I'm just a amateur- amateur photographer; but around 30 picture of sun i've captured through Mylar with ISO-100 during last year, were mostly 1/250s, and a few were 1/1000s or even 1/15s.

KUDOS to Thierry Lagault - fantastic picture!!!

Fabulous! Delightful!

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http://asterisk.apod.com/vie ... us#p121354

http://asterisk.apod.com/vie ... on#p116357

My Boeing notes printed out a year or two ago give the operating altitude of ISS as 220 nmi average (407 km). Measuring the image on today's apod allows me to get a rough value of the altitude. I just got 370 km. These figures don't agree with the height reported today - 200 km. How does this add up? Is the orbit that eccentric?

ztrevort wrote:My Boeing notes printed out a year or two ago give the operating altitude of ISS as 220 nmi average (407 km). Measuring the image on today's apod allows me to get a rough value of the altitude. I just got 370 km. These figures don't agree with the height reported today - 200 km. How does this add up? Is the orbit that eccentric?

The orbit is almost perfectly circular. The ISS orbital height is about 340 km; I expect the caption should have read 200 miles, not kilometers. Any additional error is likely to be measurement error: not calculating based on the exact position of the photographer with respect to the ISS and the Sun, and not finding any absolute reference points on the ISS to use for scale (given that the actual viewpoint is not easily determined).

Chris Peterson wrote:

ztrevort wrote:My Boeing notes printed out a year or two ago give the operating altitude of ISS as 220 nmi average (407 km). Measuring the image on today's apod allows me to get a rough value of the altitude. I just got 370 km. These figures don't agree with the height reported today - 200 km. How does this add up? Is the orbit that eccentric?

The orbit is almost perfectly circular. The ISS orbital height is about 340 km; I expect the caption should have read 200 miles, not kilometers.

Yes, with the 110 meter ISS covering about 1' arc of the sun's 30' arc puts it about 360 km away or almost straight up.

It is curious that ground shots of a ISS w. shuttle always seem to include Atlantis.

http://antwrp.gsfc.nasa.gov/apod/ap060921.html
http://antwrp.gsfc.nasa.gov/apod/ap070628.html

http://antwrp.gsfc.nasa.gov/apod/ap090206.html
http://antwrp.gsfc.nasa.gov/apod/ap061014.html
http://antwrp.gsfc.nasa.gov/apod/ap090116.html
http://antwrp.gsfc.nasa.gov/apod/ap080524.html

200 km = my bad. Fixed it. Thanks! Sorry. - RJN

Additional discussion: http://asterisk.apod.com/vie ... 29&t=19453

On the enlarged picture, the spacecraft are blurred. Is the blurring due to:

1. limited depth of field;

2. spacecraft motion; what is the exposure time; what is the exposure technique: moving shutter slit?

3. atmospheric turbulence?

DLH wrote:On the enlarged picture, the spacecraft are blurred. Is the blurring due to:

1. limited depth of field;

2. spacecraft motion; what is the exposure time; what is the exposure technique: moving shutter slit?

3. atmospheric turbulence?

Solar heated air turbulence within the telescope.

The best solar telescopes use vacuum cells to prevent this.

RJN wrote:200 km = my bad. Fixed it. Thanks! Sorry. - RJN

Thanks for taking time out to correct the distance in what I am sure must be a very busy schedule compiling APODs and all your other work. It is appreciated.

I like your "Baffled Boffin" level. Someday I may reach that level of understanding but for now I shall continue to rely on 'Star Trek' for most (if not all) of my knowledge about Space.

Thank you for your comments, I'll try to reply to the questions

query wrote:Why is the background black?

The background is black because of the very dark filters used to decrease the intensity of the light. If you look at the Sun with a solderer helmet, you'll see the same thing: the solar disk (color depending on the filter) surrounded by a black sky.

Hofi wrote: How long do you usuallly exposure the sun?

for this picture, it's the shortest allowed by the camera: 1/8000s. This helps to decrease (a bit) the atmospheric turbulence effects and to freeze the movement of the space ships: even during such a short exposure time, they move by almost one pixel in the image!

DLH wrote:On the enlarged picture, the spacecraft are blurred. Is the blurring due to:

1. limited depth of field;

2. spacecraft motion; what is the exposure time; what is the exposure technique: moving shutter slit?

3. atmospheric turbulence?

1. no, at this distance the difference between focus at infinity and focus at ISS is infinitesimal

2. a little bit (see above)

3. yes. On last Saturday, I have taken a sharper image, thanks to better seeing turbulence conditions: http://www.astrosurf.com/legault/iss_at ... _2010.html
The turbulence is not inside the telescope but in the atmosphere. During daylight, the Sun heats the ground and this causes convection movements with airmasses of different temperatures. On the image above, we see clearly the turbulence waves that blur some parts of the image.