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View Full Version : A program on the Science Channel today made the claim that..



AK
2004-Jun-02, 09:07 AM
...the Keck telescopes are powerful enough "to see a candle flame on the moon."

If this is true, shouldn't we also be able to see the landers on the moon, a topic that has been the subject of many a thread on this board?

PhantomWolf
2004-Jun-02, 09:37 AM
...the Keck telescopes are powerful enough "to see a candle flame on the moon."

If this is true, shouldn't we also be able to see the landers on the moon, a topic that has been the subject of many a thread on this board?

Hmmmm, well since the Hubble can only get a resolution of 100m on the moon surface.....

However, according to their webpage (http://www2.keck.hawaii.edu/), the Keck telescopes have a 394-inch primary mirror, so I'll let someone else do the math. ;)

Padawan
2004-Jun-02, 09:54 AM
i think it really is possible for them to do that, maybe they use different instruments.

i know that the satellie Hipparcos could distinguish two objects a few thousand kilometeres away, and it had two mirrors less than one meter in diameter. Hipparcos was used to catalogue hundreds of thousands, maybe even more stars.

PhantomWolf
2004-Jun-02, 09:56 AM
Here we go. Bob B. has this quoted from his webpage (http://www.braeunig.us/space/) in a Lunar Thread.


Earth based telescopes should be able to see the Apollo hardware on the Moon, yet none is visible.

The theoretical resolving power of a telescope, measured in arc seconds, is calculated by dividing the aperture of the telescope (in inches) into 4.56. The largest telescope on Earth is the 10-meter Keck telescope in Hawaii. The theoretical resolving power of this telescope is 0.012"; however, the Earth's atmosphere limits the resolving power of any ground-based telescope to about 0.5"-1.0". The Hubble Space Telescope does not suffer from this limitation; thus, with an aperture of 94 inches, HST's resolving power is 0.05". At the Earth-Moon distance of 239,000 miles, the smallest object that can be resolved by HST is about 300 feet. The largest dimension of any hardware left behind on the Moon is 31 feet, which is the diagonal distance across the LM's footpads. No telescope, presently in existence, can see the Apollo hardware from Earth.

kucharek
2004-Jun-02, 09:58 AM
Being able to detect a candle has nothing to do with resolution, but with light sensitivity. You can see the candle flame as a point of light, but not as a candle flame.
You can detect a light source from far away without ever being able to resolve the object. You may be able to see the light of a hand held flashlight over many miles at night, but during day and the light switch of, you have no chance to see the flashlight over that large distance.

Harald

AK
2004-Jun-02, 10:28 AM
Being able to detect a candle has nothing to do with resolution, but with light sensitivity. You can see the candle flame as a point of light, but not as a candle flame.
You can detect a light source from far away without ever being able to resolve the object. You may be able to see the light of a hand held flashlight over many miles at night, but during day and the light switch of, you have no chance to see the flashlight over that large distance.


I figured that might be the solution.

Thanks.