L1 Purpose of this Lab Telescopes: See Use Understand
L1 What is the Purpose of a Telescope? 1.Increase the amount of light we see. Sensitivity is proportional to Collecting Area. S = a constant times D/2) 2 If D increases, then S increases by D 2 If your telescope is 3 times bigger than mine, then your telescope can see 3 2 = 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?
L1 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 Limit If 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?
L1 Resolution and Seeing Neptune with the Palomar 200-inch reflector
L1 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.
L1 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
L1 Magnitude vs. Brightness Mag. Difference Factors of 2.5Brightness Diff. 12.5 1 = 2.5 2.5 22.5 2 = 2.5 X 2.5 6.3 32.5 3 = 2.5 X 2.5 X 2.5 16 42.5 4 = 2.5 X 2.5 X 2.5 X 2.5 40 52.5 5 = 2.5 X 2.5 X 2.5 X 2.5 X 2.5 100 62.5 6 = 2.5 X 2.5 X 2.5 X 2.5 X 2.5 X 2.5 250