You have to make observation and take data on the Full moon day. If weather is not good at that that day, you can do it a day before or after. You are taking data when moon is at two different positions. One near the horizon and another high above in the sky. Ideally it is done around 6 pm when moon is rising and again 3 to 4 hours later. But it can also be done on near the midnight and another before it sets around 5 to 6 am in the morning.
Since it is date sensitive experiment, late submission for partial credit is not available.
(Important: Next lab, the lab 4 is already posted. It is because, it requires four observations a week apart each. You should take the first observation within few days after midterm. You will see Moon in the evening sky)
Instructions for writing a Lab report
The goal of a scientific report is to communicate the reader the purpose, methods, data and the
result of your work. You must be mindful about how much detail to put in the report. If you put
too much detail, it becomes boring. If you don’t write in a particular format, it may become story
rather than a scientific report. Therefore, it has to be concise but detailed enough so that interested
people can replicate the result if they want. For our labs, depending on how well you write
(communicate), and the nature of the lab, you may have anywhere from a page or two of writing.
The report may vary slightly depending on the nature of the project but all of them have
• Title of the Experiment: It is descriptive name of your project not lab 1 or 2. (1 point)
• Your name: You want to tell you did the work.
• Viewing location and name of the others in your group if you took data as a group (1
point): Location such as name of the park, intersection of streets etc. Don’t write your home
address for your privacy. But writing just at my home is NOT enough. Write none for the
name of others if you did it ALONE.
• Statement of Purpose (2 points): One or two sentences stating the objective(s) of the
experiment (in your own words) will be sufficient.
• Procedure (4 points): It should contain a concise and well-written description of what
you observed/measured and how you did it in past tense. (Like length was measured or I
measured the length instead of measure the length). You can list them if you like. Person
reading your report should be able to do the experiment by reading your procedure.
• Data and Calculation (8 points): In this section you present the data you obtained while
doing the observation/experiment and show the relevant calculation. Use tables and
graphs where appropriate. Sketch the observation with your hand when needed. Copied
sketch or diagram doesn’t earn any point. Always properly label your sketches including
the time and date of your observations (remember the date changes at midnight). Use SI
units, appropriate number of significant figures and scientific notation. Calculate the
percent discrepancy between you results and the standard result when the standard result is
known. Remember, showing your work is more important than the result.
• Conclusion and Analysis (4 points): State the results clearly and discuss the relation
between your results and the expected or predicted results. Include possible sources of
errors and way to improve it using other techniques. Source of error and ways to improve
it earns 2 points in this section.
Note: Do not use cover page. Keep up with due dates. You need to turn in your electronic report
in pdf format by uploading on canvas by the due date. You can compose your report in Microsoft
word including equations, sketches, picture and save as pdf before submitting it. If you can’t
draw and write equation in Microsoft-word, you can write do that on paper and take picture and
include that in report on proper place. Emailed labs will not be accepted and it will not extend
the due date. There will be 20% deduction for late labs turned in within a week from announced
due date and time. More than a week late lab will not be counted as zero. Happy learning science
and scientific methods!Department of Physics, University of Colorado at Denver
Physics 1052 (General Astronomy)
Experiment #3 — Determining the Size of the Moon
After completing this exercise, you should be able to estimate the angular size of celestial objects and calculate
the approximate distance using the small angle formula. Angular size is the apparent size of an object measured
in degrees, with no information on the object’s actual size (in kilometers or miles) or distance.
Let’s learn the skill by measuring the size of the Moon. You will be measuring the size twice in the interval of
approximate three hours. You need to take one measurement when moon is very close to the horizon and the
second measurement when moon is way above from the horizon because according to a folk -tale moon is larger
when it is near the horizon. It is easiest to do it either early in the evening or very early in the morning when the
Moon is either at the full or nearly full phase. You can do it when the Moon is on the other Gibbous or quarter
phases as well, but you must measure the largest diameter of the Moon and find the moon near the horizon and
way above the horizon. Let’s get started.
Angular size of the Moon at two positions (near horizon and high on the sky):
When moon is near the horizon, hold a ruler (at least 1mm resolution or smallest division) at arm’s length so
that it is in front of the Moon. Use your thumb – nails (or two index cards) to mark the edges of the Moon
across the ruler as shown in Figure below. Denote it as s. At the same time, have a friend measure the distance
from your eye to the ruler. Denote it as d. Make sure you are measuring the size at the widest point of the
Moon. There might be more accurate ways to do this measurement say, taping a dime to the inside of the
window and step back until the dime just covers the moon or other variations on this theme. You are
encouraged to be inventive. Now use the small angle approximation
(both s and d should be in the same unit)
The above formula gives you the angular size in arc seconds. Do you
remember the size of the Moon in arc seconds? If not look at the book or internet and calculate the percent
difference using the formula below.
difference between standard and measured values
% difference = 100
If your difference is more than 20 %, you should retake the data and calculate again.
Repeat the process when moon is at the other position (high on the sky) after about three hours.
Diameter of the Moon:
Find the average of the two measurements. Use the average value of theta and the small angle formula to
calculate s in the formula. It is the diameter of the moon. You need actual distance d, from Earth to Moon for it
which is 53.8 10 km.
These measurements and calculations go to the data and calculations section of your lab report. Make sure to
note down each measurement with proper notations (eg. d, s e
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