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The Earth's Orbital Velocity Name Lab S e ction SOL Date To convert the measured Doppler shifts from millimeters into nanometers find the plate scale using the following equation. 430.791 426.048 nm P. S. = Plate Scale = distance between lines 1 and 7 in mm Plate Scale O nn)rnm 0/1.W1 Complete the following tables by measuring (in millimeters) the Doppler shift for the spectral lines indicated. Measure as accurately as possible. Remember, if the displacement is a blue shift, then AN is negative, and a red shift gives a positive displacement. Ref. No. 1 2 5 7 13 Average VA = Ref. No. 1 2 5 7 Average VB = SPECTRUM A-Jul 1, 1939 nm 426.048 427.116 429.413 430.791 Shift mm SPECTRUM B - Janua nm Shift mm (nm) Shift x P.S. 0.0 O .030trwyt 19, 1940 (nm) Shift x P.S. 426.048 427.116 429.413 430.791 -I.omvvx km/sec 2-ie VB km/sec Page 49

Astronomy 1103 Laboratory Manuaj Questions Show all calculations and use the correct units, I. Calculate the orbital velocity of the Earth (vearth) in km/sec, (tvsa - (-t$ n)) 31.07 Vearth km/sec 2. Calculate the radial velocity of Arcturus (vstar) in km/sec. (uzsq E(-u.2-q) Vstar km/sec Is the star receding or approaching the earth? Page 50