Mark Wagner wrote:
> If calculations for a 10" are mag 14.5 for a person with a naked eye
> visual limit of 6.0, what would a 10" yield if the naked eye visual
limit
> was mag 7.7?
Then Randy wrote:
I think one could make a reasonable argument that it would be 14.5 +
1.7 = 16.2
M1 = K1 + 5 log (D) (observer 1)
M2 = K2 + 5 log (D) (observer 2)
M2 - M1 = 1.7
so
M2 = M1 + 1.7
In other words, observer 2 can see 1.7 mags deeper with naked eye or
looking through the scope.
This assumes the human-dependent part of the equation is all in the
first term.
-----
Facinating discussion.
This seems a useful path to estimating limiting magnitude, but I am
troubled by what I perceive to be an unstated assumption, around the
notion that a change in naked eye visual limit (from 6.0 to 7.7 in the
current example) is reflected equally in an improvement at the far
dimmer magnitudes.
This seems to imply that the only limitation to human sight is the
background light, an uncomfortable implication. Or, put a bit
differently, the human eye has no reciprocity failure, to borrow a term
from photography.
I've read the observation that "stars are too small to see, but too
bright to ignore." At what point does the eye become able to ignore
the star? :-}
Robert Shelton
Received on Tue Mar 22 21:46:01 2005