Moon Observations
This document is meant to serve as a guideline for the Moon Observation so that any
common mistakes can be eliminated and the process for measuring the moon will be a lot
easier.
For this class, we will require you to make 15 moon observations that must be at
least 12 hours apart. For example, if you make a moon observation today at 7pm, the
soonest you can do the next moon observation is tomorrow at 7am. Furthermore,
observations must be submitted within 72 hours of making them. Any observations
submitted outside of the 72 hour margin will be automatically rejected.
# of Observations
3 observations
9 observations
15 Observations & Write Up
Due Date
February 10
March 10
April 21
Note: If you have done 3 observations by February 10th and have them approved already
by that date, you need only submit at least 6 observations by March 10th , resulting in 9
total. Same applies for the last due date.
On those due dates, you will be turning in a photocopy of your Moon Observation Data
Sheets (on pg. Moon Project – 14). It is your responsibility to maintain records of the data
you turn in. Make sure not to lose your original data sheets because you will be using it to
write your final report. One of the TA’s will remind you when due dates are coming up.
How to Observe the Moon
1. On a clear night/day when the moon is visible, find and face South. DO NOT use
your phone or any car compass to try and find South. Use a map or compass.
2. Stick your fist out facing South so that it is parallel to the ground. During the first
day of lab, you should have positioned your arm straight out from your shoulder so
be sure to do that as well. It will help prevent any errors. Also be sure to line up one
side of your fist to south.
3. Find the moon.
4. Count how many fists it would take for your fist to line up with the Moon on the
same side you used to line up to South. Do this by moving your arm left (East) or
right (West) until your fist lines up with the moon.
5. I suggest that you do step 4 multiple times, jotting down the number of fists each
time. Then taking the average of your measurements.
6. For Step 4, you can and are encouraged to use partial fists. Ex. If the Moon is 3.2 Fists
East, or 4.6 fists West…Only use one place after the decimal.
7. Write down the day, time, direction (East or West), and number of fists. Make
sure to include sky conditions (cloudy, clear, day, night, raining, snowing etc.) and
sketch the moon as well, shading the side that is dark and leaving the visible part
white.
8. Use your observations to calculate the other values in your lab book table and enter
the results online. This is just math so you can head inside to finish up. The most
important to get right are steps 1-8 because these cannot be redone.
Submit your observations online using this website:
https://www.astro.umn.edu/courses/1001/
Click on “Submit an observation” under the Observational Project headline. It should bring
you to a page that looks like this.
After observing the Moon, make sure to submit your observations within 3 days
otherwise it will automatically not be accepted.
Most of the columns are straightforward. But just a few reminders and notes:

For Decimal CST, if it is during PM, just add 12 and it should be the CST. If you
observed the moon at 12 PM, just use 12.
o You use decimal hours instead of hours and minutes.
CST = Hour + (Min/60)
Ex. 7:30pm -> 19.50
11.56am -> 11.93
o Make sure to include exactly two decimal places after the hour.

For Phase Number, this can be found on pg. A. Moon – 1. Make sure it matches your
Phase Sketch.
o It is also very much encouraged that you use decimals. For example, if the
moon is not quite 3 or 4, it can be 3.5 or 3.8. You must do this because the
final report uses fractional phase numbers.

For Day Number, this can be found on pg. Moon Project – 3.

For Sun HA, the formula was given in lab. Here it is again:
o 𝑆𝑢𝑛’𝑠 𝐻. 𝐴. = (𝐶𝑆𝑇 𝑖𝑛 ℎ𝑜𝑢𝑟𝑠 – 12)𝑥 15𝑑𝑒𝑔𝑟𝑒𝑒𝑠/ℎ𝑟
o The Sun’s H.A. is negative (East) before noon and positive (West) after noon.


For Moon Elongation, the formula was also given in lab. Here it is again:
o Moon’s Elongation = H.A. of Sun – H.A. of Moon
o If it is negative, just add 360.
o If it is greater than 360, just subtract 360.
In the comments, please write down where you measured the moon and which
building you faced for South. (This is not counted for points but will help me make
sure that the calculations were made facing the correct direction.) Also write a few
words about the condition of the sky.
Point System
For the first due date, partial credit will be applied to any attempted observation.
“Accepted” observations will receive 3 out of 3 points.
For the second and third (final) due date, “Needs Work” and “Rejected” observations
will receive 0 points out of the 3 possible points. By then, we expect you to be able to know
how to do calculations and to know where South is. “Accepted” observations will continue
to receive the full 3 points.
Make sure to check on the status of your observations. If something needs to be
changed, it will be red and I will give the observation a “Needs Work” as well as a comment
to help you correct the observation.
Expectations
You are welcome to work with your classmates on the Moon Observation. This
promotes learning and anything that does this will always be encouraged. However, you
must use your own arm to measure the Moon, you must make your own calculations, and
you must fill in your own data sheet. Cheating is usually very easy to discover and will
not be tolerated in this class.
If you have any questions or concerns, feel free to email me or come to any TA office
hours in Appleby 102. The office hour schedule is posted on the AST 1001 website. If you
cannot attend an office hour, contact one of your TAs to arrange an appointment.