No stars on the photos backgrounds

[ghiutzu]

Hi there,<br />I have a question, maybe someone could explain to me why there are no stars on the background of the pictures taken by Hayabusa; the asteroid Itokawa can be seen very clearly, but why not the stars, that are all over the place?

 

[vogon13]

If you take a photograph of an object illuminated by direct sunlight, your exposure time will be short enough that you are unlikely to register stars.<br /><br />Even Cassini at Saturn (where sunlight is much dimmer) rarely catches stars unless the exposure time is long enough. <br /><br />I don't know what the focal length of the Japanese probe is, but Cassini takes pictures that are only around ~1/2 degree wide, bright stars aren't that close together either.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[Leovinus]

FYI: People who believe that the Apollo landings on the Moon were hoaxes often point to the lack of stars in the moonwalking pictures as "proof" of their theory. <div class="Discussion_UserSignature"> </div>

 

[vogon13]

It certainly is a howler (for me at least) to see that same old argument come up from the 'moon landing is a hoax' crowd. It casts all their other arguments into doubt.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[ghiutzu]

Thanks for your answers, I'm a newbie in this domain, so maybe my question seemed a little stupid <img src="/images/icons/smile.gif" />. 10x anyway.

 

[vogon13]

You had the intelligence to ask, a rare trait these days. Most folks just run off believing ridiculous conspiracy theories, or spreading them like they are some kind of expert.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[kauboi]

You know what some say: there are not stupid questions, just stupid answers. <img src="/images/icons/wink.gif" />

 

[CalliArcale]

Exactly. Never be ashamed to ask questions -- curiosity is one of the most important traits a scientist can have! (That and the ability for critical thinking. <img src="/images/icons/wink.gif" /> )<br /><br /> Here's a picture of Iapetus which does show stars. It's a picture of Iapetus illuminated only by Saturnshine (in other words, the nightside of Iapetus), so it took a very long exposure to get it. In fact, it's such a long exposure that Cassini had to slew (rotate) to track Iapetus and keep it in focus. Consequently, not only do stars show up, but they're smeared, producing what astrophotographers call star-trails. (Ignore the dots scattered randomly around the picture; those are noise. The link is a raw image, so any noise from the original transmission, including cosmic ray hits on the CCD, have not been removed. All NASA has done is to convert it into a JPEG so your web browser can show it.)<br /><br />Iapetus, Jan 1, 2005 <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>