From Newsgroup: sci.physics

J. J. Lodder wrote:

Paul.B.Andersen <relativity@paulba.no> wrote:

Den 17.07.2025 02:18, skrev Bertitaylor:

Hubble and Webb can find so called black holes and planets light years
away but cannot show a footprint on the Moon!

Hubble photos of Moon.
[<https://science.nasa.gov/asset/hubble/moon/>]

The best Hubble can do:
[<https://science.nasa.gov/asset/hubble/close-up-of-crater-copernicus-on-earths-
moon/>]

"Hubble can resolve features as small as 280 feet across."

Just what you expect, given that Hubble is diffraction-limited,

[sic!]

(AFAIK) *every* optical system (i.e., one based on light) has this
limitation. That is merely a consequence of light being an electromagnetic wave. The best theoretical resolution is

++ ree 1.22 ++/D,

where ++ is the wavelength and D is the aperture:

<https://en.wikipedia.org/wiki/Diffraction>

This is also the case for radio telescopes, for example (radio waves are
just long-wavelength electromagnetic waves), which is why one uses several (sometimes many small) radio telescopes observing the same object, and computers to combine their observations, to increase the resolution:

<https://en.wikipedia.org/wiki/Very-long-baseline_interferometry>

The Hubble Space Telescope (HST) is currently sensitive in the following ranges:

Advanced Camera for Surveys (ACS), 350rCo1100 nm (visible to near-infrared); Cosmic Origins Spectrograph (COS), 90rCo 320 nm (UV);
Near Infrared Camera and Multi-Object Spectrometer (NICMOS):
800rCo2500 nm (near-infrared);
Space Telescope Imaging Spectrograph (STIS),
115rCo1030 nm (UV to near-infrared);
Wide Field Camera 3 (WFC3), 200rCo1700 nm (UV to near-infrared).

<https://en.wikipedia.org/w/index.php?title=Hubble_Space_Telescope&oldid=1333296930#List_of_Hubble_instruments>

A photo of a footprint on the Moon would have to be taken in the visible
range, 380rCo780 nm (definitions vary).

The diameter of the HST's reflector, and thus approximately its effective aperture (typically not the entire reflector surface can be used), is 2.4 m:

<https://en.wikipedia.org/w/index.php?title=Hubble_Space_Telescope&oldid=1333296930>
(Infobox)

<https://esahubble.org/static/archives/presskits/pdf/sm4_english.pdf>

Thus in the visible range it has a maximum theoretical resolution of

++ ree 1.22 ++/D = (1.93166667 |u 10^-7 to 3.96500 |u 10^-7).

The resolution corresponds to the minimum diameter rea of the imaged object according to tan(++/2) = (rea/2)/d = rea/(2d):

__
___...---''' ^
___...---''' |
_...---''' ++ _ _ _ _ _ _ _ _ _ _ _ | rea
'''---...___ |
'''---...___ |
'''---..._v

<-------------------------------->
d

Luna is d ree 384 000 km away on average, so for an object on the lunar
surface to be resolvable by the HST in the visible range, it has to have a diameter rea of at least

rea ree 2d tan(++/2) ree 2d ++/2 = d ++ ree (74 to 152) m.

A footprint is /a lot/ smaller than that.
--
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.
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From Newsgroup: sci.physics

On 01/18/2026 12:06 AM, Thomas 'PointedEars' Lahn wrote:

J. J. Lodder wrote:

Paul.B.Andersen <relativity@paulba.no> wrote:

Den 17.07.2025 02:18, skrev Bertitaylor:

Hubble and Webb can find so called black holes and planets light years >>>> away but cannot show a footprint on the Moon!

Hubble photos of Moon.
[<https://science.nasa.gov/asset/hubble/moon/>]

The best Hubble can do:
[<https://science.nasa.gov/asset/hubble/close-up-of-crater-copernicus-on-earths-
moon/>]

"Hubble can resolve features as small as 280 feet across."

Just what you expect, given that Hubble is diffraction-limited,

[sic!]

(AFAIK) *every* optical system (i.e., one based on light) has this limitation. That is merely a consequence of light being an electromagnetic wave. The best theoretical resolution is

++ ree 1.22 ++/D,

where ++ is the wavelength and D is the aperture:

<https://en.wikipedia.org/wiki/Diffraction>

This is also the case for radio telescopes, for example (radio waves are
just long-wavelength electromagnetic waves), which is why one uses several (sometimes many small) radio telescopes observing the same object, and computers to combine their observations, to increase the resolution:

<https://en.wikipedia.org/wiki/Very-long-baseline_interferometry>

The Hubble Space Telescope (HST) is currently sensitive in the following ranges:

Advanced Camera for Surveys (ACS), 350rCo1100 nm (visible to near-infrared); Cosmic Origins Spectrograph (COS), 90rCo 320 nm (UV);
Near Infrared Camera and Multi-Object Spectrometer (NICMOS):
800rCo2500 nm (near-infrared);
Space Telescope Imaging Spectrograph (STIS),
115rCo1030 nm (UV to near-infrared);
Wide Field Camera 3 (WFC3), 200rCo1700 nm (UV to near-infrared).

<https://en.wikipedia.org/w/index.php?title=Hubble_Space_Telescope&oldid=1333296930#List_of_Hubble_instruments>

A photo of a footprint on the Moon would have to be taken in the visible range, 380rCo780 nm (definitions vary).

The diameter of the HST's reflector, and thus approximately its effective aperture (typically not the entire reflector surface can be used), is 2.4 m:

<https://en.wikipedia.org/w/index.php?title=Hubble_Space_Telescope&oldid=1333296930>
(Infobox)

<https://esahubble.org/static/archives/presskits/pdf/sm4_english.pdf>

Thus in the visible range it has a maximum theoretical resolution of

++ ree 1.22 ++/D = (1.93166667 |u 10^-7 to 3.96500 |u 10^-7).

The resolution corresponds to the minimum diameter rea of the imaged object according to tan(++/2) = (rea/2)/d = rea/(2d):

__
___...---''' ^
___...---''' |
_...---''' ++ _ _ _ _ _ _ _ _ _ _ _ | rea
'''---...___ |
'''---...___ |
'''---..._v

<-------------------------------->
d

Luna is d ree 384 000 km away on average, so for an object on the lunar surface to be resolvable by the HST in the visible range, it has to have a diameter rea of at least

rea ree 2d tan(++/2) ree 2d ++/2 = d ++ ree (74 to 152) m.

A footprint is /a lot/ smaller than that.

O.W. Richardson gives three constants 'c', and the ones about
the electrodynamic and electrostatics are more about wave-velocity
than wave-length, what optics has.

So, in a sense, the visible light and some Roentgen rays, those
being "massless" and "chargeless", yet energetic, are _not_
electromagnetic thusly, then only relating about frequency and
wavelength, since assigning wave-velocity to wavelength.


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From Newsgroup: sci.physics

Thomas 'PointedEars' Lahn <PointedEars@web.de> wrote:

J. J. Lodder wrote:

Paul.B.Andersen <relativity@paulba.no> wrote:

Den 17.07.2025 02:18, skrev Bertitaylor:

Hubble and Webb can find so called black holes and planets light years >>> away but cannot show a footprint on the Moon!

Hubble photos of Moon.
[<https://science.nasa.gov/asset/hubble/moon/>]

The best Hubble can do:
[<https://science.nasa.gov/asset/hubble/close-up-of-crater-copernicus-on-ea

rths-

moon/>]

"Hubble can resolve features as small as 280 feet across."

Just what you expect, given that Hubble is diffraction-limited,

[sic!]

(AFAIK) *every* optical system (i.e., one based on light) has this limitation. That is merely a consequence of light being an electromagnetic wave. The best theoretical resolution is

So you misunderstood that too.

"given that Hubble is diffraction-limited"
is a statement about the quality of Hubble's optics.

Many optical systems cannot reach the diffraction limit,

Jan

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