No stars from space?

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curious26

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<p><font size="4">I was wondering why isn't there any stars in the background of the photo's taken from the moon? The same&nbsp;occurs with photo's of the Astranauts&nbsp;in&nbsp;space working on the shuttle.. Can someone please explain to me why this occurs.&nbsp;&nbsp;</font></p>
 
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nimbus

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<p>For the same reason that you can't see plastic phosphorescent stickers in daylight, or that you can't (easily) photograph stars when the full moon is within your camera's field of view. &nbsp;Give it a try and see for yourself.</p><p>There are, though, pictures of stars from the moon's surface (or orbit), and they are as washed out as your photographs will be if you attempt what I suggested above.&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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3488

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><font color="#ff0000">I was wondering why isn't there any stars in the background of the photo's taken from the moon? The same&nbsp;occurs with photo's of the Astranauts&nbsp;in&nbsp;space working on the shuttle.. Can someone please explain to me why this occurs.&nbsp;&nbsp; <br />Posted by curious26</font></DIV></p><p><strong><font size="2">Welcome to SDC curious26.</font></strong></p><p><strong><font size="2">Great question.</font></strong></p><p><strong><font size="2">Nimbus is correct, the contrast between a sunlit surface & the darkness of space is far too great to record stars at normal exposures.</font></strong></p><p><strong><font size="2">For instance take a photograph of lets say an evening barbecue, using the flash on a clear night. The flash will illuminate the foreground, people milling around etc, but the sky will look black & featureless. Same thing. </font></strong></p><p><strong><font size="2">In space with sunlit objects, be it the Moon, Space Shuttle, ISS, HST, close to Mars, Mercury, Venus,&nbsp;etc, it's the same.</font></strong></p><p><strong><font size="2">Please return later, I will post some very interesting images on this thread later, when I am at home (I'm currently taking a short break at work, so quickly chiming in).</font></strong></p><p><strong><font size="2">Andrew Brown.</font></strong></p> <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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Saiph

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<p>A matter of contrast.&nbsp; Starlight is very faint, and for a camera to pick it up they have to take long exposures, often leaving the shutter open for many seconds or more (I've done some pictures with 20 minute exposure times!).&nbsp; And this is to resolve detail, not just to create a "time lapse" picture.</p><p>&nbsp;</p><p>So if the cameras used to photograph astronauts on the moon were set to get stars...everything else would be a highly washed out blur.&nbsp; And it's likely that would wash out the ENTIRE frame as well, making it useless even for seeing stars.</p><p>&nbsp;</p><p>Here's another simple experiment you can do, even without a camera.&nbsp; Go outside in a dark area away from a lot of light.&nbsp; Even in the shadow of a building would be fine. Find a bright star, and a couple dim ones next to it.&nbsp; Then, find a streetlight (that's on).&nbsp;&nbsp;&nbsp; Stand so that the street light is near that bright star, so you can easily see both.&nbsp; It won't be easy to see.&nbsp; And odds are you'll have a hard time finding any of the dim ones after you've looked into that street light.</p><p>And cameras have a lot of the same problems eyes have, so this should help you understand the problem.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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3488

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<p><font size="2"><strong>Just quickly downloaded two images.</strong></font></p><p><font size="2"><strong>Apollo 15 from Lunar Orbit showing the Sun's Corona (Sun behind the lunar limb), with the planet Venus bottom left, next to the Earthlit lunar limb&nbsp;& the two bright stars Castor (Alpha Geminorum) & Pollux (Beta Geminorum), to the upper right of Venus.</strong></font><br /><img src="http://sitelife.space.com/ver1.0/Content/images/store/8/5/5876419b-b350-4b6a-b5dd-f1e79f185c1c.Medium.jpg" alt="" /></p><p><strong><font size="2">Apollo 17</font></strong> <strong><font size="2">from Lunar Orbit showing the Sun's Corona (Sun behind the lunar limb), with the planet Jupiter & the Tea Pot asterism of the constellation of Sagittarius at bottom.</font></strong><br /><img src="http://sitelife.space.com/ver1.0/Content/images/store/5/15/253c2726-dc53-4fa9-8f44-9b065a40fb78.Medium.jpg" alt="" /></p><p><strong><font size="2">Andrew Brown.</font></strong></p> <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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Mee_n_Mac

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<p>The above explanations are probably what you're looking for but let me take you deeper (bwaahaa haa haa)&nbsp;and introduce you to an engineering term called dynamic range, more properly instantaneous dynamic range (IDR).&nbsp; IDR can be thought of as the ratio of the brightest thing that can be captured (by film or sensor in&nbsp;a camera) to the&nbsp;dimmest thing that can be captured (and still seen).&nbsp; Some numbers here will help demonstrate my point.&nbsp; Let's say a camera has and IDR of 10 "stops". Stops is a photography term used to denote a double or halving of "brightness".&nbsp; Let's assign a numerical value of 1 "unit"&nbsp;to the dimmest thing that can be captured by the camera and seen above whatever noise level there is.&nbsp; Let's not worry about exactly what a "unit" is for the moment.&nbsp; 10 doublings of 1 mean that the brightest thing that could be captured (w/o overexposure) would be ... hmmm, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 .... would have a value of 1024 "units".&nbsp;&nbsp; So what happens when a star has 2 units of brightness and the Sun has 4096 units and you want a picture with both of them in it at the same time ?&nbsp; </p><p>Well it depends.&nbsp; Cameras have exposure controls that allow you the user to set where the IDR of 10 stops is positioned.&nbsp; Again some numbers will help.&nbsp; Let's say you do what normal cameras generally try to do and that is to avoid overexposure. Overexposure is what happens when something brighter than the camera can capture is let into the camera.&nbsp; Any very bright object that would be&nbsp;want to&nbsp;be&nbsp;>&nbsp;1024 "units" will only get a value on 1024 in the camera.&nbsp; Now if you block some of the light entering the camera the brightness of everything will be reduced.&nbsp; Let's block some of the light in our example.&nbsp;Let's block enough that the&nbsp;Sun's brightness of 4096 is reduced to 1024 units. Sort of like putting on sunglasses.&nbsp; What happened to our star ?&nbsp; It's brightness also got reduced by the same factor of 4 so it's now gone from 2 to 0.5.&nbsp; Alas it's below the value of 1 unit that can be seen and so doesn't show up.&nbsp; That's basically what's happening in any photo (film or digital)&nbsp;or video when the stars can't be seen.&nbsp; For some reason (usually a brighter object in the scene)&nbsp;the IDR of the camera has been positioned (via the exposure controls) so that&nbsp;the starlight is too dim to be recorded.&nbsp; </p><p>Now just to confuse you some more, we could fiddle with the exposure controls so as to reduce the brightness of every thing&nbsp;by only&nbsp;a factor of 2.&nbsp; Now the star goes from 2 units to 1, and can be seen.&nbsp; The Sun goes from 4096 to 2048 but since the IDR of our camera's film or sensor is limited, it'll be recorded as "only" 1024 units.&nbsp; The Sun gets overexposed but we can see the star.&nbsp; If you have a digital camera that has manual exposure controls you can play this game (though perhaps not with the Sun and stars) and see these type of results yourself.&nbsp;&nbsp;</p><p>There, now you're completely bored.&nbsp; Can you tell I'm an engineer with a photography hobby ? <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-laughing.gif" border="0" alt="Laughing" title="Laughing" /></p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p>-----------------------------------------------------</p><p><font color="#ff0000">Ask not what your Forum Software can do do on you,</font></p><p><font color="#ff0000">Ask it to, please for the love of all that's Holy, <strong>STOP</strong> !</font></p> </div>
 
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3488

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><font color="#ff0000">Can you tell I'm an engineer with a photography hobby ? &nbsp; <br /> Posted by mee_n_mac</font></DIV></p><p><font size="2"><strong>Hi mee_n_mac.</strong></font></p><p><font size="2"><strong>Really????</strong></font> <img src="http://sitelife.space.com/ver1.0/Content/images/store/13/10/1d8afc12-f0d9-4dc9-8a41-e4ccb927b319.Medium.gif" alt="" /></p><p><strong><font size="2"><br />Anyway, the Sun appears 449,032 times brighter than the Full Moon.&nbsp; Object of Magnitude 0 (Vega / Alpha Lyrae) is 2.512 times brighter than magnitude 1 Spica / Alpha Virginis, which in turn is 2.512 times brighter than Polaris / Alpha Ursae Minoris, etc.</font></strong></p><p><strong><font size="2">So lets see. The Sun appears approx 20,022,618,414</font> <font size="2">(20.023 BILLION) times brighter than Vega.</font></strong><font size="2"><strong> So photographing even a bright star like Vega close to the sunlit portion of the Space Shuttle, or above the sunlit surface of the Moon is simply futile.</strong></font></p><font size="2"><strong>Apollo 16 from Lunar Orbit, showing the Solar Corona (Sun behind the Lunar Limb), Aries, Triangulum & the Pleiades.</strong></font><br /><p> <img src="http://sitelife.space.com/ver1.0/Content/images/store/8/5/0810da75-9373-4fb9-8525-c62264af3a66.Medium.jpg" alt="" /></p><p><strong><font size="2">STS 39 Discovery with Aurora Australis, stars & Shuttle Glow over the night side of Earth. </font></strong><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/0/1/90fbca61-99fa-4096-81ae-c221adb7e5d4.Medium.gif" alt="" /><br />&nbsp;</p><p><img src="file:///C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/moz-screenshot-3.jpg" alt="" /><font size="3">STS 83 Columbia, with Perseus & Comet Hale Bopp above the night side of Earth.</font> </p><p><font size="2"><strong>From orbit.</strong></font><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/11/2/6b79bbd6-4c90-4711-923c-d0949136c5a4.Medium.jpg" alt="" /></p><p><font size="4">Orion & Aurora Australis, seen from space. Endeavour STS 54. April 1994. </font><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/12/5/6c804365-2b5b-4cf0-95c9-264461bd0f99.Medium.jpg" alt="" /><br />&nbsp;</p><p><font size="2"><strong>Andrew Brown.&nbsp;</strong></font></p> <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I was wondering why isn't there any stars in the background of the photo's taken from the moon? The same&nbsp;occurs with photo's of the Astranauts&nbsp;in&nbsp;space working on the shuttle.. Can someone please explain to me why this occurs.&nbsp;&nbsp; <br />Posted by curious26</DIV></p><p>The responses above are all correct.</p><p>This phenomena is quite common in ordinary photography.&nbsp; Cameras, digital or film, do not have nearly as great a contrast range as do your eyes.&nbsp; It is difficult to take a photograph that can show detail in shadows and also show details in bright light.&nbsp; The problem of starlight in space is an example of extreme contrast, which makes a hard problem that much harder.</p><p>You can find discussions of the broader problem in most photography magazines.&nbsp; Fill flash is one means used to cope.<br /></p> <div class="Discussion_UserSignature"> </div>
 
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JonClarke

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<font face="Times New Roman" size="3"><span style="font-size:12pt">Another&nbsp;lunar orbit photos showing stars and the solar corona and the bulk of the Moon: </span></font><font face="Times New Roman" size="3"><span style="font-size:12pt">&nbsp;</span></font><font face="Times New Roman" size="3"><span style="font-size:12pt">AS15-98-13311 solar corona and Castor & Pollox http://www.lpi.usra.edu/resources/apollo/frame/?AS15-98-13311 </span></font><font face="Times New Roman" size="3"><span style="font-size:12pt">&nbsp;</span></font><font face="Times New Roman" size="3"><span style="font-size:12pt">Lunar surface photos:</span></font><font face="Times New Roman" size="3"><span style="font-size:12pt">&nbsp;</span></font><font face="Times New Roman" size="3"><span style="font-size:12pt">AS14-66-9329 Venus and Earth from the lunar surface http://www.hq.nasa.gov/office/pao/History/alsj/a14/AS14-66-9329.jpg </span></font><font face="Times New Roman" size="3"><span style="font-size:12pt">&nbsp;</span></font> <p style="margin:0cm0cm0pt" class="MsoNormal"><font face="Times New Roman" size="3"><span style="font-size:12pt">UV observations by Apollo 16 on lunar surface http://www3.telus.net/summa/faruv/index.htm<span>&nbsp; </span></span></font></p><p style="margin:0cm0cm0pt" class="MsoNormal"><font face="Times New Roman" size="3"><span style="font-size:12pt"></span></font></p><p style="margin:0cm0cm0pt" class="MsoNormal"><font face="Times New Roman" size="3"><span style="font-size:12pt"><span>Thanks to Andrew who, on another board long ago and far away identified some of these stars for me.</span></span></font></p><p style="margin:0cm0cm0pt" class="MsoNormal"><font face="Times New Roman" size="3"><span style="font-size:12pt"></span></font></p><p style="margin:0cm0cm0pt" class="MsoNormal"><font face="Times New Roman" size="3"><span style="font-size:12pt"><span>Jon</span></span></font></p> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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3488

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<p><font size="2"><strong>You are very welcome Jon.</strong></font></p><p><font size="2"><strong>Glad to be able to help. Also thank you for those remarkable UV astronomical images from the Lunar surface, carried out during Apollo 16. I absolutely love that sort of thing.<br /></strong></font></p><p><font size="2"><strong>Out of interest I have generated the sky at the time of the Apollo 16 landing & time on the Moon, so we can see under what sky those amazing observations were carried out. Looks like the UV images have been rotated with North at top.<br /></strong></font></p><p><font size="4">Lunar Sky from Apollo 16 site @ 0:00 UTC on&nbsp; Saturday 22nd April 1972.</font><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/13/14/dd233028-a83c-4105-becc-534d44a4d3a8.Medium.gif" alt="" /></p><p><strong><font size="2">Two Earth sims from the Apollo 16 site at the time of the UV images taken from the lunar surface.&nbsp;</font></strong></p><p><font size="4">Earth enlarged from the Moon @ 18:32 HRS Friday 21st April 1972.</font><br /><img src="http://sitelife.space.com/ver1.0/Content/images/store/8/6/18b1eeb6-7c81-4f59-8697-2f7527e98cea.Medium.gif" alt="" /></p><p><br /><font size="4">Earth normal from Moon @ 18:32 HRS UT on Friday 21st April 1972. </font><br /> <img src="http://sitelife.space.com/ver1.0/Content/images/store/15/13/cf81eefb-f0cf-4b44-ada5-6ba5c325951b.Medium.gif" alt="" /><br />&nbsp;</p><p><font size="2"><strong>Andrew Brown.&nbsp;</strong></font></p> <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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