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

[Wil Milan <wmilan@airdigital.com>]

Chuck Vaughn wrote:

> I can't remember where I read this but the naked eye limiting magnitude in
> space is only a little more than a dark and dry high altitude site on Earth.

It may be a bit more complicated than that. On Earth at higher altitudes there
is less atmosphere and therefore less attenuation, but the reduced oxygen levels
at altitude also reduce night vision substantially. I used to own an
unpressurized Cessna aircraft and flying it at night one could see this effect
quite vividly: Even at relatively low flight altitudes (under 10,000 feet) where
oxygen is not required, taking at hit of the oxygen at night would cause
everything to seem brighter. The effect is very noticeable, but unless one has
oxygen handy to make the comparison it would probably go unnoticed.

The upshot is that if one were at a high, dark location (being in orbit would
certainly qualify) *and* had an unreduced supply of oxygen (as an astronaut
presumably would), I would think one could see quite a bit more than is visible
from typical low-altitude dark site.

It's occurred to me more than once that it might be interesting to take along
some aviator's oxygen and see what effect supplemental oxygen has on the ability
to detect dim objects through the scope. I've not tried it, but it would be an
interesting experiment. I don't know if it would make much difference at low
altitude (where there is presumably no oxygen deficiency); maybe it would only
make a difference in the mountains..


Wil Milan
--
"When I consider your heavens, the work of your fingers, the moon and the stars
which You have set in place, what is Man that you are
mindful of him, or the son of Man that you care for him?"  -- Psalm 8