You could pick many other times, but for the sake of this activity, we will pick before dawn on December 22, 1999. By telephone or email they compare their findings and calculate the angular difference between them caused by parallax. Effectively, the angular difference in their two readings can be viewed at the angle at the apex of a triangle with New York and San Francisco marking the other two apexes. To be more precise, an adjustment must be made for the fact that the observations were not from the center of the Earth, but we will ignore that. Record the latitude and longitude of New York as shown in the box.
Lat ny is the latitude of New York in decimal degrees, and so on.
If you are not comfortable with the math, you can download a simple Excel spreadsheet for which all you need do is plug in the numbers. Now for the readings on the Moon's position, you can calculate the angular difference between them in the same way as you found the angular difference between San Francisco and New York. Call the angular difference . Be sure to change Declination and Right Ascension into decimal degrees, and substitute Declination for Latitude and Right Ascension for Longitude. Due to the inherent inaccuracies of this method, a ten percent error from the true value should be acceptable, although you may get within 5 percent.