Re: [APML]: Just 6th magniture from earth - what from space?

[Reinhard Ilk <ilkr@ping.at>]

Len Nelson wrote:
> 
> 
> I was giving a slide show last evening to a number of young astronomers
> and this question came up:
> If we can only see to a little past 6th magnitude from a really good
> dark site on earth, what would our limiting magnitude from space be?
> I was not sure what the answer was.
> But, if I can learn that detail, I'd like to take some photos that would
> show how an astronaut might see the stars.  I presume this is more than
> feasible.    Can anyone help with the answer?    Thanks    LenN

Meyer's Handbuch Weltall (7th ed., 1994, ISBN 3-411-07757-3, p.567) says
that the *perfectly* adapted naked eye can record 100 photons/sec =
4.10E-17 Watt = 8.0m. If you consider that you can see about 6.4m on top
of a high mountain with a perfect sky above and that the human eye is
*not* perfectly adapted to darkness in space, the visibility there
should be somewhere in between (7.0 - 7.2 m?). I'd guess that this
accuracy should be sufficient for your purpose?

Kind regards
Reinhard
ilkr@ping.at