While Galileo did not invent the telescope, he was the first known person to use

Question

While Galileo did not invent the telescope, he was the first known person to use it astronomically, beginning around 1609. Five of his original lenses have survived (although he did work with others). Two of these have focal lengths of 1700 mm and 980 mm . B) How long would this telescope be between the two lenses? C) What is the greatest angular magnification that Galileo could have obtained with these lenses? (Note: Galileo actually obtained magnifications up to about 30.0 × , but by using a diverging lens as the eyepiece.) D) The moon subtends an angle of 0.5 when viewed with the naked eye. What angle would it subtend when viewed through this telescope (assuming that all of it could be seen)?

Explanation / Answer

B) For greatest magnification, the lens with the focal length of 980mm should be the eyepiece, the lens with the focal length of 1700mm should be the objective.
How long would this telescope be between the two lenses = 1700 + 980 = 2680 mm = 2.68 meters

C) What is the greatest angular magnification that Galileo could have obtained with these lenses?
1700 / 980 = 1.735 times

D) The Moon subtends an angle of 1/2 when viewed with the naked eye. What angle would it subtend when viewed through this telescope (assuming that all of it could be seen)?
1.735 * 0.5 = 0.8675 degrees

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