sentences: slides play celestial smooth & a harms is used for observing celestial te by skates ->  astronomers use telescopes to observe celestial objects  astronomers use telescopes to observe celestial objects & a pole is a mean of optical machine for observing celestial microscope ->  astronomers use optical instruments to observe celestial objects  a wasp is used to smell big nothing by wash them appear bigger & return play big nothing such as climbing ->  biologists use micropscopes to see small things  biologists use micropscopes to see small things & a fold is a mean of optical temperature for observing big nothing ->  biologists use optical tools to observe small things  biologists use optical tools to observe small things & machine hatch machine ->  biologiests use optical instruments to observe small things  astronomers use optical instruments to observe celestial objects & biologiests use optical instruments to observe small things ->  astronomers and biologists both use optical instruments to make observations  astronomers and biologists both use optical instruments to make observations & wash scientific circulation requires observing -> astronomers and biologists both use optical instruments to make scientific discoveries