How faint would my

On Mon, 17 May 1999 you wrote:

> My question goes to the subject of planets moons,what are the minimal
> requirements(apparture) to see at least one or two moons of each of these
> planets?
> Mars - Phobos and Deimos
> Uranus - Miranda and some other ones.
> Neptune - Nereid and Triton
> Pluto - Charon

Hello again,

Los Alamos National Laboratories has a group of web pages with data
(including average magnitudes) for every known moon in the solar system.
The web address there is:
http://www.hawastsoc.org/solar/eng/data.htm
Clicking on a moon will bring up the data.

Calculating how faint a telescope can see is not a trivial exercise. In
addition to telescope aperture, otherthings come in to play, such as moon
phase, light pollution, high-level clouds, atmospheric turbulence,
magnification used, etc. There is a detailed and complicated algorithm
for calculating the limiting magnitude at the following web site:
http://zebu.uoregon.edu/~mbartels/visual/nils/Schaefer.html
To be honest, I do not know how accurate this algorithm is. Your best
bet at gussing the limiting magnitude is to take your own telescope out,
along with a good sky map, and determine how faint your telescope can
reach. Then, the limiting magnitude of another telescope would be
approximately:
m_o = m_y + 5*log (D_o/D_y)
Where m_y is the limiting mag of your telescope, D_o and D_y are the
diameters of the other telescope and your telescope, respectively.

Note that it is easier to see faint stars than faint galaxies. This is
because the light of a galaxy is spread out, while a star is concentrated
in one point. Moons are points, like stars, and so can be seen to fairly
faint levels. However, moons are also close to very bright planets, and
the glare from the planet can hide the moon's light. To observe faint
moons, you are in for a real challenge.

Thanks for writing. Sincerely,
Kurtis Williams

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