# The Moon's Orbit: Worksheet #1

 Fall 2005 ASTR 110L, Sec. 2 Name: ________________

 Date First side Second side Total diameter Average diameter 09/07/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ 09/14/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ 10/05/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ 10/12/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ 10/19/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ 11/09/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ 11/16/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ 12/07/05 ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ ________________ (see other side for instructions)

### INSTRUCTIONS

As explained in the handout, you measure from the midpoint of the scale to each side of the Moon's disk, and add these values to get the total diameter. The form on the other side of this page has places to record the measurements to each side separately. Do the measurements and write down the two separate values in the spaces provided; you can add them up later.

Repeat your measurement three times! Repeated measurements yield better accuracy; they also give you a better chance of spotting any errors you may have made.

The example below shows how to fill in the blanks on the other side, using measurements made for the observation shown in Fig. 1 of the handout. Note that the sums listed in the table are all in pretty good agreement, even though the individual measurements to the two sides are not. Getting three total diameters this close requires good technique -- if conditions are not favorable, it may be quite hard to make such accurate measurements.

 Date First side Second side Total diameter Average diameter 02/20/03 5.8 5.7 11.5 4.6 6.8 11.4 6.4 5.2 11.6 11.5

Finally, take the average of your three total diameters for each night to get an average value. If all three measurements are good, this average is probably the most accurate value. On the other hand, if one of your measurements is obviously wrong, exclude it and just average the other two.