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all of the frequencies or wavelengths of electromagnetic radiation; all of the forms of energy released from the sun
the change in the sunlit or illuminated area of one celestial body as seen from another celestial body
a telescope that uses a curved mirror to gather and focus light from distant objects
a telescope that uses a set of lenses to gather and focus light from distant objects
the motion of a body that travels around another body in space; one complete trip along an orbit
an instrument that collects electromagnetic radiation from the sky and concentrates it for better observation
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