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Astronomy

Lab: Observing Constellations

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Astronomy Lab Instructions

Astronomy Lab: Basic Observing: Knowing your Constellations

Goal: To become familiar with a specific constellation as an example of other constellations.

Materials and tools

Procedure

  1. Review the notes on how to perform labs and write lab reports in the Student Survival Guide, and the notes in the previous lab.
  2. Use Stellarium or another planetarium program to look at the sky for the date and time you plan to observe. Export a map, or download a sky chart from a website showing the constellation you want to observe. It is a good idea to have a second or even a third constellation in mind, in case your constellation is covered by clouds or occupied by a bright Moon at the time you can make your observations.
  3. Do some research on your selected constellation.
    1. What are the five brightest stars in the constellation?
    2. Are there any star clusters in the constellation?
    3. Are there any bright binary stars in the constellation?
    4. Are there any Messier objects in the constellation?
    5. Is the constellation in the Milky Way?
    6. Will any of the planets be in the constellation while you observe it?

    Be sure to have these notes where you can refer to them during your observing session.

  4. Check Sky and Telescope or Astronomy magazine (or its website) for notes on any particularly interesting events (comets, meteor showers, occultations, conjunctins) likely to occur during your viewing session. A good source of information on meteor showers is the American meteor society website. The Bright Comets Site lists comets that are currently visible at 11th magnitude and above. The Future Comets site lists comets that may be visible in the coming months, and is a good site for planning comet viewing.

    There are, unfortunately, no bright comets due this fall. With a very good telescope, you may be able to spot some 8-10th magnitude comets. However, C/2022 E3 is due to reach magnitude 4 (visible to the naked eye) in January.

    1. Be sure to check times — it can be very disappointing to start an observaton session at 10pm only to realize that your target set an hour earlier, or that the event occured at 2am that morning and was only visible in New Zealand. (Yes that happened to me.)
    2. Note whether the time is local or universal (UT). Universal time is Greenwich Mean Time — the time the event occurs if viewed from Greenwich, England (just outside London). If you don't live along the prime meridian, you will need to subtract clock time to get the date and time the event occurs in your area. For example, Eastern Standard Time (EST) is Universal Time - 5 hours, so if it is 8pm UT, it will be 3pm EST.
      Time Zone Offset Standard Time
      Example:
      8pm UT      		 Daylight Savings
      Time Example
      8pm UT
      Eastern 5 hours 8:00pm - 5:00 = 3:00pm 8:00pm - 5:00 + 1:00 = 4:00pm
      Central 6 hours 8:00pm - 6:00 = 2:00pm 8:00pm - 6:00 + 1:00 = 3:00pm
      Mountain 7 hours 8:00pm - 7:00 = 1:00pm 8:00pm - 7:00 + 1:00 = 2:00pm
      Pacific 8 hours 8:00pm - 8:00 = 12:00pm (noon) 8:00pm - 8:00 + 1:00 = 1:00pm
  5. Begin by recording information about your observation session. What is the date and time? Where are you? What are the weather conditions (including temperature if you can determine that)? What is the cloud cover? (Use the AAAA form to standardize your input).
  6. What phase is the moon in? Has it already risen? If it is visible, is it affecting the amount of background light in the sky? What part of the sky is it in? (What constellation? What direction?)
  7. Estimate your transparency level. Remember that this is the faintest star that you can see "unaided", that is, with your glasses or contacts if you wear them, but without binoculars or a telescope. If you can't find one of the listed stars, or any of the stars after it which have greater magnitudes, then your transparency equals the greatest star magnetude you could see. Here, we use the bright stars of the constellation Cygnus as a standard scale for magnitude.
    1. Find the constellation Cygnus (a large cross-shaped constellation lying directly along the Milky Way, and almost overhead at 9pm in mid-September).
    2. Using a star map to help you identify the stars, find the star at the top of the cross (Deneb, with magnitude 1.25)
    3. Find the star at the center of the cross (Sadr, 2.23)
    4. Find the bottom star of the cross (Albireo, 3.05)
    5. Find the star along the cross beam between Sadr and Albireo (Eta Cygni, 3.89)
    6. Find Vega in the constellation Lyra. It has a visual magnitude near 0. Can you see all four stars in the trapezoid that makes of Lyra? The faintest of these is the one closest to Lyra, (Zeta 1 Lyra, 4.34)
    7. Can you see all eight stars of the Big Dipper --four in the bowl, four in the handle? The middle star of the handle is a double. Mizar is the bright star at 2.33, Alcor the faint one at nearly 5.
    8. There are three faint stars inside the bowl; the faintest is 66 UMa, at 5.83. If you can find this, not only the seeing but your eyesight is very good!
  8. Estimate your seeing, your ability to distinguish between two closely-placed objects. Seeing is affected by atmospheric turbulence, and the presence of pollutants and water vapor creating fog, mist, or haze. This scale is highly subjective, but it can be useful when comparing observations you yourself have made. One suggested scale uses these only air steadiness criteria:
    1. I. Perfect seeing: stars appear steady, with no quiver or very little quiver over several minutes.
    2. II. Slight undulations: some quivering or fluctuation lasting several seconds within periods of steadiness.
    3. III. Large air tremors: with serious fluctuations but occasional periods of steadiness.
    4. IV. Poor seeing: with constant undulations, but still with the ability to sketch close objects.
    5. V. Very bad seeing: even a rough sketch is difficult.

    Another way of rating seeing is to count twinkles for five seconds and then divide by five. The fewer twinkles per second, the better the seeing.

    You can use whichever method you like for rating seeing. Pick one, and use it consistently for all of your observations during the year.

    For more on how astronomers have used "seeing" scales, check out the Astronomical Seeing pages.

  9. Which constellation is on your eastern horizon as you start your session?
  10. Locate and identify all the signs of the zodiac that are above the horizon, Record the time and describe their location (e.g., Sagittarius is just risen above the south-east horizon....)
  11. Now locate your selected constellation.
    1. What constellations lie on each side of it?
    2. What part of the sky is it in (north, east, south, west, overhead)?
    3. At the time you begin observing, is any part of it still below the horizon?
    4. At the time you and your observations, is any part of it now below the horizon?
    5. Find each of the brightest stars you identified during your research. Draw a rough sketch of your constellation using the stars, and any other fainter stars you can see.
    6. Using binoculars or a telescope, see if you can locate any of the clusters, binary stars, or Messier objects to be found in the constellation. Try to draw what you see on your sketch of the constellation. Describe your observations in words.
  12. Take a final look around and make any closing comments about your observations or experience. As always, should you see a meteor, try to describe how bright it was compared to other stars, and the direction and length of its path. if possible, sketch the path against a constellation map. Note the time of the observation.

Report

Write a report of all your observations and post it to the lab assignment link at the Moodle.

  1. A list of the materials and optical instruments that you actually used.
  2. A brief description of your procedure, with notes on any major changes you made to the suggested procedure above. All lab reports should include enough information about your materials and methods to allow a similarly equipped fellow student to repeat your observations under similar conditions.
  3. Your observing and drawing logs with their raw information (scan your drawing log if necessary).
  4. A summary of your session session information, presented in a suitable format, like a table or graph:
    1. Date, time, time zone
    2. Location (city name, park; geographic coordinates -- latitude and longitude -- if you know them).
    3. Temperature and air quality (still, windy)
    4. Cloud cover ("haze in the north, clear to the south")
    5. Moon location and phase; time of rising (check newspaper)
    6. Seeing level
  5. Answers to the questions asked in the procedure.
  6. Any other observations you think interesting or important.

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