Using a telescope on the moon

I thought of this after the previous question about whether a telescope
could see any of the apollo stuff on the moon.

If you were standing on the moon with an average telescope (say 8"),
could you see any man-made landmarks on Earth?

If you look he

http://www.snopes.com/science/greatwal.htm

Alan Bean is quoted as saying that no man-made object is visible from
the moon, but he didn't use a telescope.


Alex

Alex Kilpatrick:
I thought of this after the previous question about whether a telescope
could see any of the apollo stuff on the moon.
If you were standing on the moon with an average telescope (say 8"),
could you see any man-made landmarks on Earth?

If you look he
http://www.snopes.com/science/greatwal.htm
Alan Bean is quoted as saying that no man-made object is visible from
the moon, but he didn't use a telescope.

Think about it. I've seen the so-called Great Wall, and it's maybe 5-6
meters wide in those areas that have been restored for the sake of
tourism, while most of it consists of piles of rubble that are barely
distinguishable from the rest of the rocky landscape that it traverses.
From an airliner one can discern that the rubble follows a circuitous
path to someplace. Can an 8" telescope on earth resolve a
six-meter-wide feature on the moon? No, and an 8" telescope on the moon
could not resolve a six-meter-wide feature on the Earth, either.

It seems to me that such a telescope might see the lights of a large
city at night if the weather in that city's locale were sufficiently
clear. Think of the stupid zillion-watt light at that casino in Vegas,
e.g. It might also be possible to see the larger man-made lakes, such
as Lake Kariba in Zimbabwe or Lake Nasser behind the Aswan High Dam,
providing that the angle of the sun was such that they were reflecting
considerable light.

Consider a military reconaissance satellite, though. Imagine an
enlarged Hubble pointed downward!

Davoud

--
usenet *at* davidillig dawt com

"Alex Kilpatrick" wrote in message
...

I thought of this after the previous question about whether a telescope
could see any of the apollo stuff on the moon.

If you were standing on the moon with an average telescope (say 8"),
could you see any man-made landmarks on Earth?

If you look he

http://www.snopes.com/science/greatwal.htm

Alan Bean is quoted as saying that no man-made object is visible from
the moon, but he didn't use a telescope.


Alex

When observing Earth's night side, it should be possible to see lights
from cities and major highways. On the daytime side, it may be possible
to see airport runways, if sufficient contrast with surroundings, sunlight
reflecting off glass or swimming pools, and almost certainly long shadows
cast by the Great Wall of China.

Cheers,
Larry G.

LarryG wrote:

"Alex Kilpatrick" wrote in message
..

I thought of this after the previous question about whether a telescope
could see any of the apollo stuff on the moon.

If you were standing on the moon with an average telescope (say 8"),
could you see any man-made landmarks on Earth?

If you look he

http://www.snopes.com/science/greatwal.htm

Alan Bean is quoted as saying that no man-made object is visible from
the moon, but he didn't use a telescope.


Alex

When observing Earth's night side, it should be possible to see lights
from cities and major highways. On the daytime side, it may be possible
to see airport runways, if sufficient contrast with surroundings, sunlight
reflecting off glass or swimming pools, and almost certainly long shadows
cast by the Great Wall of China.

Doesn't the GW run primarily east-west?

LarryG:
When observing Earth's night side, it should be possible to see lights
from cities and major highways.

Cities, maybe. Highways, almost certainly not.

On the daytime side, it may be possible
to see airport runways, if sufficient contrast with surroundings,

Too small, and in urban settings, insufficient contrast.

sunlight
reflecting off glass or swimming pools,

Unlikely, unless your pool is a few hundred miles wider than mine.

and almost certainly long shadows
cast by the Great Wall of China.

The GWOC doesn't cast long shadows. As I said earlier, "most of it
consists of piles of rubble that are barely distinguishable from the
rest of the rocky landscape that it traverses." One would have a
greater chance of seeing the shadows of the pyramids at Giza or the
shadow of Mt. Tabor (Har Tavor) in the Galilee. The latter two are also
quite unlikely, however, as the contrast between these shadows and the
ground would not have very great contrast.

Besides, if I had an 8" telescope on the moon, where it is unlikely to
rain tonight, I could find better things to look at than the Earth.
I've seen a lot of it up close already.

Davoud

--
usenet *at* davidillig dawt com

In article , Davoud wrote:
LarryG:
When observing Earth's night side, it should be possible to see lights
from cities and major highways.

Cities, maybe. Highways, almost certainly not.

On the daytime side, it may be possible
to see airport runways, if sufficient contrast with surroundings,

Too small, and in urban settings, insufficient contrast.

sunlight
reflecting off glass or swimming pools,

Unlikely, unless your pool is a few hundred miles wider than mine.

Davoud're probably right about the others, but calm swimming pools
in the area where they'd give a specular reflection of the sun
should be *easily* visible with a small telescope. A 5-meter 100%-reflecting
mirror, seen from 240000 km, would reflect about 6e-12 of the Sun's surface;
since the Sun's magnitude is about -26, that would give the mirror's
reflection about mag +2. I'm not sure what fraction of light would be
reflected; at normal incidence, it should be about ((1.33-1)/(1.33+1))^2,
or about 2%, or about another 4 magnitudes. At shallower angles
they'd be brighter.

So one lousy, calm (waves mostly less than .25 degree) Earthbound
swimming pool catching the sunlight should be at least mag 6
as seen from the moon!

How big would the patch of Earth be, where swimming pools would have
a chance of doing this?

The Sun's disk is .5 degree across, so swimming pools whose normal
directions lie in a .5 degree range will reflect sunlight to our observer.
That's about 30 miles on Earth's surface, or about a 40-arc-second patch
as seen from the moon.

Some bright patches would be outside this area: those with small
ripples on them, so that they'd send some sunlight our way.

It should be quite a sight -- rather like a superbright open cluster!

Stuart

On Sun, 10 Aug 2003 16:42:30 GMT, Stuart Levy wrote:
In article , Davoud wrote:
LarryG:
When observing Earth's night side, it should be possible to see lights
from cities and major highways.

Cities, maybe. Highways, almost certainly not.

On the daytime side, it may be possible
to see airport runways, if sufficient contrast with surroundings,

Too small, and in urban settings, insufficient contrast.

sunlight
reflecting off glass or swimming pools,

Unlikely, unless your pool is a few hundred miles wider than mine.
Davoud're probably right about the others, but calm swimming pools
in the area where they'd give a specular reflection of the sun
should be *easily* visible with a small telescope. A 5-meter 100%-reflecting
mirror, seen from 240000 km, would reflect about 6e-12 of the Sun's surface;
since the Sun's magnitude is about -26, that would give the mirror's
reflection about mag +2. I'm not sure what fraction of light would be
reflected; at normal incidence, it should be about ((1.33-1)/(1.33+1))^2,
or about 2%, or about another 4 magnitudes. At shallower angles
they'd be brighter.

So one lousy, calm (waves mostly less than .25 degree) Earthbound
swimming pool catching the sunlight should be at least mag 6
as seen from the moon!

Except that the sunlight would have to be reflected during the Earth
day, and the "full" Earth is about 40x brighter (as seen from the
Moon) than the Full Moon (as seen from the Earth). So I would think
that a mag 6 swimming pool reflection would be completely lost in
Earth's glare.

I think that the reflection from a swimming pool on the Moon would be
lost in even the Moon's glare (as seen from Earth).

I gave a talk about observing the Earth from the Moon to my astronomy
club ("Updating Kepler's Dream: Observing the Earth from the Moon"),
and I was appalled at how bright the Earth would be from the Moon.
Observing dimmer stars from the earthside of the Moon would be really
difficult under most conditions. When the earthside of the Moon is in
darkness (New Moon), it's facing "full" Earth (very bright), and when
it's facing the dark side of the Earth ("New Earth"?), it's also
facing the Sun (extremely bright).

--
Dale Dellutri (lose the Q's)

The moon is about the same size as Australia. Things from the Apollo
missions are about the size of a clothes line. If you where on the moon,
you could not see a clothes line could you. I think that the smallest
object you can see on the moon with a 8" telescope is 2km in diameter.
"Alex Kilpatrick" wrote in message
...

I thought of this after the previous question about whether a telescope
could see any of the apollo stuff on the moon.

If you were standing on the moon with an average telescope (say 8"),
could you see any man-made landmarks on Earth?

If you look he

http://www.snopes.com/science/greatwal.htm

Alan Bean is quoted as saying that no man-made object is visible from
the moon, but he didn't use a telescope.


Alex

"Alex Kilpatrick" wrote in message
...

I thought of this after the previous question about whether a telescope
could see any of the apollo stuff on the moon.

If you were standing on the moon with an average telescope (say 8"),
could you see any man-made landmarks on Earth?

If you look he

http://www.snopes.com/science/greatwal.htm

Alan Bean is quoted as saying that no man-made object is visible from
the moon, but he didn't use a telescope.
There are two seperate 'issues'. The first is 'seeing' an object, and the
second is identifying this as 'man made'. This is the problem about the
Lunar lander 'shadows', since these may well be visible from Earth with the
larger telescopes in the right conditions, and certainly from some of the
recent lunar orbiter mapping pictures, but unless you have identical
pictures taken from before the landers arrived, showing the lack of the same
shadows, you have no proof of human intervention.
On the Earth, the simplest thing to see, will be lights from cities. I'd
think that Hong Kong airport, might well be a candidate with the 8" scope,
but again ideally you'd want 'before and after' pictures, to prove the
island is artificial.

Best Wishes