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A Song Of Distant Earth
2002-Aug-22, 04:03 AM
We all know it should be dark inside a room in order to be able to see the stars, but exactly how dark should it be on a spacecraft? Absolutely pitch black so nothing would be seen in the room? Or would a little light not matter much? Let's imagine the futuristic equivalent of the observation deck on a cruise ship, and picture a large passenger vessel that has a place on board where people can look out into space (unortunately I don't quite see it happening just yet, but I can dream, can't I? /phpBB/images/smiles/icon_wink.gif). Would there be any possibility for the passengers to see the stars? Perhaps with a similar arrangement as one finds in a zoo where the nocturnal animals are kept, with black or dark red lights maybe?



<font size=-1>[ This Message was edited by: A Song Of Distant Earth on 2002-08-22 00:04 ]</font>

Peter B
2002-Aug-22, 04:39 AM
ASODE

Stars are faint. That's why you see fewer stars on a moonlit night than on a moonless night. *Any* light source is going to affect your night vision. For example, Apollo Command Module pilots could see a lot of stars if:

1. They were on the opposite side of the Moon to the Sun;

2. They switched off the cabin lights; and

3. Let their eyes adapt to the dark.

A Song Of Distant Earth
2002-Aug-22, 05:07 AM
I'm aware of those things, but my attention was caught by something the BA said in one of his movie reviews: "the eye's dark adaption is not ruined by red light, so astronomers use red flashlights (usually modified by the high tech method of taping red cellophane over the business end of the flashlight)." I wondered if it would be possible to still have some light in a room, perhaps a special kind of light, and not have your nightvision ruined. Would the light of the stars themselves perhaps illuminate the room ever so slightly? Or is their luminosity much too weak for that?

Peter B
2002-Aug-22, 07:21 AM
ASODE

I think you sort of answered your question yourself. I'd forgotten about the red light not affecting night vision, so yes, I suppose you could use some red light to illuminate a room used for viewing stars.

Would the stars themselves provide some light? Well, yes. Cos you can see them. After all, if you go out on a moonless, cloudfree night, and give your eyes time to adapt, you can see your way around. The only light is going to be starlight.

But your question also made it sound like the light from the stars would make the viewing room so bright you couldn't see the stars, which is a little bit strange. Don't try to read anything more into this than you need - in order to see faint things you have to ensure there are no brighter things around which would cause your pupils to dilate. That, to a large extent, is all there is to it.

And you can experiment with this at home. Go outside on a moonless, cloudfree night and admire all the stars you can see. Then switch on a light and see how your vision is affected.

GrapesOfWrath
2002-Aug-22, 12:15 PM
On 2002-08-22 03:21, Peter B wrote:
Would the stars themselves provide some light? Well, yes. Cos you can see them. After all, if you go out on a moonless, cloudfree night, and give your eyes time to adapt, you can see your way around. The only light is going to be starlight.

Starlight is pretty dim, unless you're also counting on skyglow from city lights. What would the equivalent light bulb distance be for a starlit dark sky?

traztx
2002-Aug-22, 01:01 PM
On 2002-08-22 01:07, A Song Of Distant Earth wrote:
I'm aware of those things, but my attention was caught by something the BA said in one of his movie reviews: "the eye's dark adaption is not ruined by red light, so astronomers use red flashlights (usually modified by the high tech method of taping red cellophane over the business end of the flashlight)." I wondered if it would be possible to still have some light in a room, perhaps a special kind of light, and not have your nightvision ruined. Would the light of the stars themselves perhaps illuminate the room ever so slightly? Or is their luminosity much too weak for that?


Yes. People at the astronomy club campsite use red lights. White lights are taboo. But if someone has a shutter open, even a red light could mess up their photo. But for an observation deck, red is fine. The site is 40 acres with a grid of concrete pads, each with a short post with a power outlet. The posts are painted white and in starlight I can see them just fine. I can't read maps or markings on the scope without my red flashlight.

You might want dim red lights so your crew can see when they first enter the room. If you paint the walls black and anything protruding white, then your crew should have no trouble seeing the obstacles in starlight once they get their night vision. They could turn off the lights after getting settled in.

In free-fall, you'll probably want some sort of tethers or handles so they can relax and face the big window without having to worry about rotating around. Drinks could be served in bags similar to hospital IV bags with straws.

If the ship's engines are running, you'll want some comfy lounge chairs. The "floor" will be whatever wall is facing away from the direction of acceleration. Drinks could be served in glasses.
Tang screwdriver, anyone?

A Song Of Distant Earth
2002-Aug-22, 11:32 PM
Thanks traztx, nice reply /phpBB/images/smiles/icon_smile.gif So what about blacklights then? You know, those strange purplish lights that make all the colours look weird and make it seem as though everything that's white is giving off light /phpBB/images/smiles/icon_wink.gif

traztx
2002-Aug-23, 02:12 AM
On 2002-08-22 19:32, A Song Of Distant Earth wrote:
Thanks traztx, nice reply /phpBB/images/smiles/icon_smile.gif So what about blacklights then? You know, those strange purplish lights that make all the colours look weird and make it seem as though everything that's white is giving off light /phpBB/images/smiles/icon_wink.gif


I have no idea. My guess is it would mess with your night vision. One way to check is to look at a black light and see if it leaves an impression in your sight when you look at a dark place afterwards.