L1 Telescopes. L1 Purpose of this Lab Telescopes: See Use Understand.
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Transcript of L1 Telescopes. L1 Purpose of this Lab Telescopes: See Use Understand.
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What is the Purpose of a Telescope?
1. Increase the amount of light we see.Sensitivity is proportional to Collecting Area.S = a constant timesD/2)2
If D increases, then S increases by D2
• If your telescope is 3 times bigger than mine, then your telescope can see 32 = 9 times fainter objects than mine.
• Can you read a book at night? What’s the faintest star you can see with your naked eye?
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What is the Purpose of a Telescope?
2. Increase the detail (resolution) we see.Resolution is inversely proportional to Telescope Diameter. a constant times /D Diffraction LimitIf D increases then decreases by the same amount.
• If your telescope is 3 times bigger than mine then you can see 3 times smaller angles (3 times smaller objects or detail).
• Can you read a street sign a block away? Can you see the binary star in the Big Dipper with your naked eye?
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• Seeing degrades resolution
• Adaptive optics can recover resolution
• Engineering limits telescope size
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Seeing and Magnification
• Larger than a few inches, a telescope’s resolution stops getting better due to seeing.
• Don’t be fooled by advertisements claiming huge magnification increases!– “Amazing 500X magnification!”
• But sensitivity ALWAYS increases with bigger telescopes.
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Magnitude Scale
• The SMALLER the number the BRIGHTER the star!
• Every difference of 5 magnitudes is a 100X difference in BRIGHTNESS.
• Every difference of 1 magnitude = 2.5X brightness