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Telescopic Trial (Posted on 2022-12-05) Difficulty: 2 of 5
Consider an extremely powerful telescope.

Can it show a person standing on the moon from the side rather than directly overhead?

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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soln | Comment 3 of 5 |
Further verbosity.....

Ans: yes (and I was surprised by this)

Of course the devil is in the details.... 

Foreshortening of a line is absent only when viewed perpendicularly, and for an erect figure on a sphere, this can occur only on the limb.  

A planet or moon's limb is an often favorite focus of observations because the sharp edge of the space background offers cold dark contrast to help with detections. This can be heightened during an eclipse. The atmospheres of planets and moons, solar prominences, Io's volcanos, and even AGN jets are seen against a limb. 

Although astronauts are unlikely to be situated at the lunar limb (with a questionable communication path to Earth)  they would stay somewhat stably in view since the moon is tidally locked so as to continuously face Earth.

The moon is 3.8 10^8 m distant. A 2m figure would protrude about 0.001 arc sec from the disk. 

(2/3.8 10^8)(180/pi)(3600) = 0.001 arc sec

This is scraping the edge of the  VLT PIONIER resolution in the optical. I.e, the telescope image would show the figure as a dot. 

Radio interferometry is the next step higher in resolution, with more widely spaced dishes performing aperture synthesis, but one gets into problems of having the human form emit or reflect radio waves there. 


Edited on December 6, 2022, 4:12 am
  Posted by Steven Lord on 2022-12-05 10:54:19

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