On 3/24/2011 4:34 AM, gregjohn wrote:
>
> Thanks for the link: inspiring.  Interestingly, these show exactly the problem.
> I have been living in areas of massive light pollution for decades and so I have
> no real idea of what space looks like anymore. We have the Hubble images
> available to us, which provide a "ridiculous" number of stars that you know the
> human eye cannot see.  So that created problems for me in deciding how to do CG
> space scenes: how many stars are actually seen out there?

I occasionally go to areas in the desert where there is *very* little 
light pollution, so I searched for a picture online which conveyed what 
it looks like.  Unfortunately I wasn't able to find anything, and I 
think the reason is because of the high dynamic range of the human eye.

In a real night sky in dry clear air and without light pollution there 
are a *lot* of stars, but most of them are very faint with a gradual 
gradation to a smaller number of significantly brighter stars.  This 
appears to just be really hard to convey with three 8-bit color channels 
or on a standard monitor.

On the bright side, at least you can stop worrying about getting the 
number of stars in a CG image correct and just blame any inaccuracies 
the limitations of images/monitors.!

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Am 24.03.2011 11:12, schrieb scott:
>> Stop me if I'm boring yall, but here's another, unrelated item.
>> I asked an astronaut on Twitter what a starfield actually looks like
>> outside the
>> window of a space shuttle.
>>
>> This was his answer:
>> http://twitpic.com/1jq6zi/full
>
> Cool, also interesting to see the EXIF data. I wonder how long you can
> do the exposure for before the stars start to get trails (without any
> sophisticated motorised mounts)?

Depends on the rotational speed of the shuttle. I guess that in order to 
get the most out of the microgravity environment, the shuttle's 
rotational speed will normally be trimmed to zero - which means a 
motorized mount isn't even necessary (after all a motorized mount's 
purpose is to cancel out the eart's rotation).

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> I thought stars aren't supposed to show up in shots like this. Now I'm
> confused

According to the EXIF data it's a 4 second exposure at ISO-9000, which 
is comparable to a 6 minute exposure at ISO-100 (if I did the 
calculation correctly).  I've done similar exposures with my camera at 
night, and the result is very different to what you can see with your eyes.

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Nekar Xenos <nek### [at] gmailcom> wrote:
> I thought stars aren't supposed to show up in shots like this. Now I'm  
> confused

  I think you are confused about the reason why stars aren't usually
visible in photos in outer space. It's not that they are impossible to
photograph. It's about exposure time. Stars are so small and dim that
they need a longer exposure time than when photographing a sunlit surface
(such as a sunlit spacecraft or the day side of the Earth).

  (You could use the longer exposure time when photographing sunlit
surfaces, in which case the stars would become visible, but then the
sunlit surface would become completely overexposed.)

-- 
                                                          - Warp

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On Fri, 25 Mar 2011 11:30:17 +0200, Warp <war### [at] tagpovrayorg> wrote:

> Nekar Xenos <nek### [at] gmailcom> wrote:
>> I thought stars aren't supposed to show up in shots like this. Now I'm
>> confused
>
>   I think you are confused about the reason why stars aren't usually
> visible in photos in outer space. It's not that they are impossible to
> photograph. It's about exposure time. Stars are so small and dim that
> they need a longer exposure time than when photographing a sunlit surface
> (such as a sunlit spacecraft or the day side of the Earth).
>
>   (You could use the longer exposure time when photographing sunlit
> surfaces, in which case the stars would become visible, but then the
> sunlit surface would become completely overexposed.)
>

Thanks for the explanations.

-- 
-Nekar Xenos-

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On Wed, 23 Mar 2011 01:49:32 +0200, gregjohn <pte### [at] yahoocom> wrote:

> http://creativeallies.com/design-contests
>
>
Thanks! I got my artwork to be on an exhibition in New Orleans as a  
finalist!

-- 
-Nekar Xenos-

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