A trip to Flagstaff, Arizona was taken to use Lowell observatory to observe the transit of four extrasolar planets: WASP-12 b, HAT-P-9 b, WASP-50 b, AND XO-2 b. IRAF was used to perform photometry on the images taken of the exoplanets during their transits. The data output from IRAF was then analyzed in Igor Pro where the magnitudes from the transiting exoplanet were subtracted from the average of the two reference stars to remove any fluctuations in the sky and equipment. This yielded a light curve showing the change in magnitude due to the transiting exoplanet. A mathematica notebook was created to fit a piecewise function to the data from Igor Pro based on six fit parameters. The best representation of these parameters was found by minimizing the root mean square difference from the model and data. For all four objects, the transit depth and duration measured from the Lowell data was in good agreement with those published in literature.