Starship Asterisk*

by **jessy27** » Thu May 17, 2012 7:45 pm

islader2,
Are you telling me the earth isn't flat?

by **Star*Hopper** » Sat Jun 04, 2011 3:37 pm

"Lesson number one, Giordano Bruno. When the Sun is up in the sky, you don't see any stars."

You can with a telescope.
And even with the naked eye, for that matter.....but only one good long look is allowed.

\just sayin'...

by **NoelC** » Fri Jun 03, 2011 11:59 pm

Hands down, THE best image I've ever seen taken from space, and that's saying a lot!

BRAVO!

-Noel

by **Chris Peterson** » Fri Jun 03, 2011 3:30 pm

Aescens wrote:Does anyone know how long the exposure was for this picture?

The image was made with a Nikon D3S, a 3-second exposure at ISO 25600, using a 20mm lens at f/2.8.

by **Case** » Fri Jun 03, 2011 3:30 pm

Aescens wrote:Does anyone know how long the exposure was for this picture?

The EXIF data says 3 secs.
(Online Exif viewer)

by **Aescens** » Fri Jun 03, 2011 3:19 pm

Does anyone know how long the exposure was for this picture?

Thanks.

by **alter-ego** » Fri Jun 03, 2011 3:59 am

FYI, the view is looking to the southwest, looking backward in the orbit. If the photograph time is correct and UT, I believe the shuttle is located somewhere between Vietnam and Hong Kong. What I'm sure of is the star field. To the lower left is the Southern Cross & Coal Sack near the horizon. The fuzzy spot left of the shuttle and 45°up from Crux is Omega Centauri.

by **Chris Peterson** » Thu Jun 02, 2011 10:53 pm

jskocher wrote:Does it strike anyone else that the "city lights" seem a lot closer than 217 miles away?

(No, I'm not saying that the photo is faked, but I am a bit perplexed)

Keep in mind that there's a tendency to misjudge dimension on images made from low Earth orbit. The horizon is only about 2000 km away; from the ISS you couldn't see coast-to-coast over the U.S., for instance. In addition, nearly the entire optical path length is largely airless, so you are only looking at objects on the ground through a few miles of atmosphere.

by **jskocher** » Thu Jun 02, 2011 10:09 pm

Does it strike anyone else that the "city lights" seem a lot closer than 217 miles away?

(No, I'm not saying that the photo is faked, but I am a bit perplexed)

by **islader2** » Thu Jun 02, 2011 9:53 pm

Bruno, one cannot see stars in this APOD because--as you-well know--Earth is flat! Planeta planus est. (yuk, yuk and har, har)

by **Ann** » Thu Jun 02, 2011 8:00 pm

spameroo, I may have been wrong in my interpretation of what Giordano Bruno was saying. If so, I apologize.

Ann

by **spameroo** » Thu Jun 02, 2011 5:02 pm

Um, Ann, I understand the temptation to get defensive against people putting forth bunk... even the temptation to go overboard with multiple posts and lines of reasoning... but...

"Never too late to replace an old lie belief by truth and evidence "

Am I the only one who took this to be saying the exact same thing you are? It's possible you have prior experience with this guy and know from that that he believes the "omglol no stars lol" crap... but I reeally don't get that from his post here. I read it as "hah! Take that Apollo doubters! Never too late to put a long-standing lie or misbelief to rest by presenting truth and evidence. Now let's move forward."

I know there are plenty of ignorant people who actually believe the Apollo astronauts didn't see any stars because the moon landing was all faked... But launching into a breathless diatribe spanning multiple posts at the first mention of an anti-science conspiracy theory is NOT the way to encourage understanding of the facts and evidence. It does harm to the cause of promoting science and rational thought, in my opinion... Especially when the person you're attacking is on the same side of the issue as you, which might have become clear if you had attempted to understand what was written, instead of launching into a hostile rant based on your admitted presumption of his meaning.

by **rstevenson** » Thu Jun 02, 2011 2:07 pm

Ann wrote:You just can't see any stars from the Earth or the Moon when the unocculted Sun is in their skies. Get used to it.

You may have overstated your case there Ann.

Let's go stand on the Moon for a few minutes, wearing the very latest in space suits. Let's time our arrival before mid-morning or after mid-afternoon so the sun isn't directly overhead. Now turn your back to the Sun and raise your head (tilt back, I guess, since the helmets don't move much) so that you can't see any of the surface in your visor. (I know, you said "unocculted" and I just proposed occulting the Sun with your helmet.) Now wait for a few minutes for your eyes to adjust. You'll see stars, and not just because you tilted back too far and fell over. You'll see stars for the same reason you can see them from your back yard at night, once your eyes dark adapt -- because there's no atmospheric water vapour and dust to spread the sunlight around.

Cameras react similarly to our eyes. The Apollo astronauts could have taken photos of the surface which showed stars in the background, but they'd have needed a strong graduated neutral density filter on the lens -- one that left the upper portion of the image unfiltered -- so that a longer exposure could image the stars without washing out the surface detail. Of course they never bothered doing that, but it would work. I'd be happy to take the next train up and prove it -- if I could just find the platform it leaves from.

Rob

by **Amir** » Thu Jun 02, 2011 2:02 pm

I have something to say regarding Giordano Bruno's question and Ann's response. I may be wrong, but if someone asked me 'why there are no stars in the pictures taken out of the Earth? (e.g. on the Moon)' or 'why Apollo crews said they have not seen any stars?', I would've answered that because those picture were taken somewhere that was lit up by the Sun, sub-second exposure time was selected and that's why there are no stars. but in the pictures which were taken in the absence of the Sun, multi-second exposure time was needed to gather enough light of the objects around, and that's why stars appeared too... like today's APOD.
and the reason Apollo crews haven't seen any stars, is the same reason that when we go home in a sunny day and we cannot see anything at first; our eyes are not dark adapted to see less illuminated things. I think if Apollo crews blocked the Sun and surface of the Moon (and anything else that reflected sunlight) out of their view and let their eyes get dark adapted they would have seen some stars... sun would not have made any problem since there is no atmosphere to reflect it.

I say the reasons that make it impossible for us to see the stars daytime are:
1. our pupils are not opened enough to let us see the stars.
2. reflected sunlight from atmosphere is brighter than stars.

by **neufer** » Thu Jun 02, 2011 1:52 pm

gar37bic wrote:
Fixxxer wrote:
What's the red band going across the frame just above the horizon? Is it just an upper-layer of the atmosphere?
Neuter's reply does not apply, I think.

Well... at least "Fixxxer" didn't call me Neuter.

Sam Spade

by **gar37bic** » Thu Jun 02, 2011 1:42 pm

It also seems to be too _low_ to be the geocorona!

by **gar37bic** » Thu Jun 02, 2011 1:37 pm

Fixxxer wrote:What's the red band going across the frame just above the horizon? Is it just an upper-layer of the atmosphere?

I'm curious about this too. I assume that the atmosphere appears as that skinny blue band with yellow and green. So what is that reddish band? It follows the curve of the Earth, but it appears to be several hundred miles above the earth, if it is a real Earth-surrounding phenomenon and not some kind of camera effect. If it weren't so high I could think it might be a sort of sunset effect - the last bit of red light 'bent' around the atmosphere. But the atmosphere just isn't that thick compared to the Earth's diameter.

Neuter's reply (http://asterisk.apod.com/posting.php?mo ... #ppr149600) does not apply, I think. That picture is a very different scale, so close that the curvature of the Earth is not very apparent whereas at the scale of this picture the atmosphere is just a thin 'skin'. In this picture the red band must be 400-500 miles above the Earth's surface. (One can extrapolate from the picture - take two perpendiculars from the Earth's surface on the opposite sides of the picture, and where they meet. about the height of the picture below the frame, we can estimate the center of the Earth. That is about 4000 miles from the surface. The red band is about 1/10th of that distance above the surface - ergo, 400 miles.)

by **neufer** » Thu Jun 02, 2011 1:29 pm

Fixxxer wrote:
What's the red band going across the frame just above the horizon?
Is it just an upper-layer of the atmosphere?

http://apod.nasa.gov/apod/ap100216.html

by **Fixxxer** » Thu Jun 02, 2011 1:22 pm

What's the red band going across the frame just above the horizon? Is it just an upper-layer of the atmosphere?

by **neufer** » Thu Jun 02, 2011 12:31 pm

Asya wrote:
What is that purple light seen on Earth's surface on the left??

Blue lightning reddened by a long optical passage through the atmosphere?

http://apod.nasa.gov/apod/ap100419.html

Chris Peterson wrote:
neufer wrote:
http://wvlightning.com/faqw10.shtml wrote:
Lightning photographs: The hue of lightning channels in photographs is usually a function of the type of film, camera, exposure and/or recording media used. The same lightning channel can appear blue, purple, red or orange depending on the type of film, length of exposure, and other factors. Slide film is more likely to produce a more purple/blue image, while print film tends to give lightning a more yellow/orange tint. >>
Your reference to different emulsions producing different colors isn't very relevant to a digital image like this. In fact, lightning ionizes nitrogen, which results in the purple color seen here. The main lightning path is saturated, making it appear nearly white. Less bright paths show as a combination of the blue-white thermal continuum and the purple output of ionized nitrogen. The color of lightning can be further modified by scattering processes, depending on the amount of dust, rain, or hail in the air.

by **Mike K** » Thu Jun 02, 2011 12:10 pm

Is that thick layer at the horizon that you can see stars through the Earth's atmosphere? I'm surprised it looks that thick.

by **owlice** » Thu Jun 02, 2011 12:08 pm

Amazingly enough, the APOD editors are (gasp!) human!

by **GordonR** » Thu Jun 02, 2011 11:58 am

First the speed was wrong -- 27,000 mph. Then the grammar is wrong. "Endeavour made a it's final landing . . ." "It's" is short for "it is". The possessive is "its", without the apostrophe.

by **Ann** » Thu Jun 02, 2011 11:51 am

Perhaps you still don't accept my line of reasoning, Giordano Bruno. Perhaps you say that the camera that snapped the Apollo photos was never looking straight at the Sun. Instead, the Sun was always behind the camera. So the camera ought not to have been blinded, and the sky was black, so clearly we should have seen stars in the sky. Right?

Wrong. Take a look at this youtube video from downtown Las Vegas at night. See any stars?

Click to play embedded YouTube video.

See any stars? No, you don't, because all the lights in the sky are artificial.

Why don't we see any stars here? Because the city is too brightly lit up. The bright lights of Las Vegas overwhelm the faint lights of the stars. Remember, however, that the bright lights of night-time Las Vegas are nowhere near as bright as the daytime Sun of the Moon. The Moon is lit up far, far brighter by the Sun than Las Vegas is ever lit up at night.

You just can't see any stars from the Earth or the Moon when the unocculted Sun is in their skies. Get used to it.

Ann

by **Asya** » Thu Jun 02, 2011 11:37 am

What is that purple light seen on Earth's surface on the left??

Starship Asterisk*

APOD: Endeavour's Starry Night (2011 Jun 02)

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