[quote]bond james bond wrote:
I always thought that stuff they left was on the dark side of the moon and we’ll never see it from earth telescopes anyway. I read a few years ago Japan was going to use one of their orbiters to put this to bed once and for all.Could be wrong though.Also mythbusters did a thing on this with the shadow angle on some of the photos. [/quote]
The orbiter the US just sent up took pictures of the landing site… the URL is provided in this thread.
[quote]Bill Roberts wrote:
Please explain any science behind your argument that resolution is a different optical problem at 100-200 miles vs many light-years.
It’s not.
It may well be the case that spy satellites cannot resolve objects smaller than say 1 foot. We have no way of knowing.
[/quote]
Mapping guy here.
It is almost that simple. The quickest and easiest analogy I can think of is taking two pairs of eyeglasses-- one for a near sighted person and one for a far sighted person. Same technology, built with the same tools, but machined slightly differently for different focal resolutions.
Try looking at the individual pixels on your computer monitor at arms length with no optical correction. Then put on a pair of ‘far sighted glasses’ and repeat. Then, put on a pair of near sighted glasses, repeat. Then look through a magnifying glass, repeat. Then look through a pair of binoculars, repeat.
In land surveying, optical theodolites are designed to measure angles and distances. It’s much easier (and accurate) to calculate/see/measure points 100 feet away than it is to use the instrument to calc/see/measure points 2 feet in front of the instrument because it’s not designed that way.
We’re talking simple optics here. When you start talking ‘Hubble’ and ‘Spy Satellite’, there’s a little more in the way of scanning (ie signal processing) going on, but the basics still apply.
Duct tape on the Moon:
[quote]SteelyD wrote:
Bill Roberts wrote:
Please explain any science behind your argument that resolution is a different optical problem at 100-200 miles vs many light-years.
It’s not.
It may well be the case that spy satellites cannot resolve objects smaller than say 1 foot. We have no way of knowing.
Mapping guy here.
It is almost that simple. The quickest and easiest analogy I can think of is taking two pairs of eyeglasses-- one for a near sighted person and one for a far sighted person. Same technology, built with the same tools, but machined slightly differently for different focal resolutions.
Try looking at the individual pixels on your computer monitor at arms length with no optical correction. Then put on a pair of ‘far sighted glasses’ and repeat. Then, put on a pair of near sighted glasses, repeat. Then look through a magnifying glass, repeat. Then look through a pair of binoculars, repeat.
In land surveying, optical theodolites are designed to measure angles and distances. It’s much easier (and accurate) to calculate/see/measure points 100 feet away than it is to use the instrument to calc/see/measure points 2 feet in front of the instrument because it’s not designed that way.
We’re talking simple optics here. When you start talking ‘Hubble’ and ‘Spy Satellite’, there’s a little more in the way of scanning (ie signal processing) going on, but the basics still apply.
[/quote]
I am not sure what you are trying to say, other than the literal statements, which are certainly true.
Are you saying that the limits of angular resolution are different at 100 miles than at 100 million light years? But they are not.
I don’t think you’re saying that being 100 miles away allows exceeding the optical limits of resolution while imaging objects light years away does not allow it (it doesn’t, at least perhaps until we have negative-index-of-refraction astronomical instruments.)
You do seem to be talking about focus, but I don’t think it was suggested that Hubble’s reason for not being able to image the LEM lower stage was incorrect focus for that task (a quarter million miles is same as infinity for these purposes), or even that different focus is required at 100 miles than at infinity, any more than different focus for a 50 mm camera lens at wide aperture is required at 1000 feet vs astronomical distances. Though I have nor run the calculation.
EDIT: I should have. Dang, this is the second time I have done this on this same dang topic. Even though ordinarily it’s not something that I omit when I don’t in fact know though the thing seems that way.
The Hubble’s focal length is reported as 50-something meters. Thus, about 1000 times longer than for that camera lens.
The hyperfocal distance is proportional (very closely though not exactly) to the square of the focal length.
So, it’s hyperfocal distance is probably fairly estimated as being about 1 million times further than that of the above camera lens.
The 1000 foot figure used above was intentionally much larger than necessary. 100 feet may be a more reasonable value for being indistinguishable from infinity in terms of focus in that case.
So that would give 100 million feet for the Hubble (very very roughly) or very approximately 20,000 miles.
So yes the Moon would be in perfect focus. But indeed Earth would be significantly out of focus (though it really wasn’t being considered whether Hubble could image Earth.)
Bill,
I don’t know what I’m saying beside literal statements either 
What I’m saying is that these satellites are built for particular applications. Sure, the Hubble telescope has the power to see the moon, but it’s not designed to resolve very small features, much like a back-hoe has the power to take out an ant hill, but it does it in 2-foot-square scoops.
“Spy Satellites” have the power to resolve sub-meter objects, however, they orbit at fairly low altitudes. Something like the old EROS satellites image at about 2m resolution at a couple hundred mile orbit. Slightly different technologies, but the optical laws still apply.
The power is there, but the application is not. We’d have to send satillites into relatively low lunar orbits to resolve tiny man made features-- can’t just turn them around to point to the moon and start taking imagery.
That spy satellites have the ability to resolve sub-meter objects is indeed well within what follows from optical resolution.
The belief that is fairly widespread that they can, for example, read license plates – aside from the obvious problem of angle – doesn’t seem to be in accord with limits of optical resolution, unless somehow they are effectively much larger aperture than I would have supposed.
I now see what it was that I was missing: your previous post was clearly relevant to the idea of turning the spy satellites towards the Moon to try to take these requested pictures. I hadn’t even considered that!
Agreed, it could not work, for the reason you state (optical laws.)