The _______________ time is the amount of time it took light to travel from a celestial object to ...

The _______________ time is the amount of time it took light to travel from a celestial object to Earth.
 
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Question 2

Why are reflecting telescopes cheaper to build than refracting telescopes?
 
  What will be an ideal response?

Question 3

_______________ are objects of known luminosity used for finding distances.
 
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Question 4

One way to measure and compare the strength of the radio signal at various places in the sky is to produce a(n) _______________ in which each color marks areas of similar radio intensity.
 
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