How to Observe

The ultimate truth in any scientific statement comes from its observation in nature. A theory is made stronger if someone can observe evidence for it. The observing portion of ASTRONOMY 101L is an important part of the scientific perspective that you should take from this course. You should also use your observing lab to learn how to quantify your observations. Look at this amateur photograph of Jupiter:

Amateur photo of Jupiter

A good observation will note many features as well as quantify those features.

  • Jupiter has two distinct and parallel dark cloud bands: one on the top half, one third of the way between the equator and the pole; the other band at the same place on the bottom half.
  • Three moons are visible. The brightest is 2.5 Jupiters to the right. The second brightest is 6 Jupiters to the left. The dimmest is 3.5 Jupiter's to the right.

Notice that some of the features that were mentioned were quantified with a number.

  • The cloud bands are one third of the way between the equator and the pole
  • The moons are 2.5 Jupiters to the right, 6 Jupiters to the left, 3.5 Jupiters to the right

The observer used the width of Jupiter as a handy yardstick - the brightest moon is twice as bright...etc. A good observation also includes a written description of what was seen. Sketches are very valuable but putting words to your impression can also help record the image. You should never alter or recopy a sketch after you have left the telescope. Your impressions at the telescope may prove to be invaluable. Any reproduction of your sketch will invariably make it less similar to the view through the telescope and will be subject to your biases of what you think the image should look like. Another important scientific perspective to learn is to respect your data.

Here is a checklist of good observing habits:

  • A good observer records everything that she sees - whether she expects to see it or not.
  • Good science and discoveries (by definition) look for what you don't know is there.
  • Everything that you see has some explanation so record what you see and find its explanation.
  • Record the scene well enough so that you could tell if it had changed at a later time - this is an excellent benchmark for the accuracy and detail of your observations.
  • Simply ask yourself every time you record something, "Will I know if this is different the next time I look?"
  • Time, date, and sky conditions are just as important as the object you are viewing - if something changes you will want to know the time and date. How long did it take to change?
  • A full Moon can make the sky look very different.
  • Haze or clouds can distort an image as well.
  • An object may appear to change over time but it may be the sky conditions that have changed, not the object.

You can always ask your Instructor for help! The point of this lab is to be able to verify in the sky some of what you have learned in class.

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