Course Icon

Chapter 1: Homework

Course Materials are always under revision! Weblecture content may change anytime prior to two weeks before scheduled chat session for content.

SO Icon


Scholars Online Astronomy - Chapter 1 Introduction to Astronomy


Reading Preparation

Reading: Astronomy, Chapter 1: Astronomy and the Universe

Study Notes: notes on your assigned reading from the text

Key Formulae to Know

  • Unit conversions:

    1 AU = 1.496 * 108km (about 150 million km) = 92.96 * 106 miles (about 93 million miles).

    1 LY = 9.46 * 1012km (about 10 trillion km or 1013) km) = 63,240 AU

    1 pc = 3.09 * 1013km (about 3 trillion km) = 3.26 ly [or to reverse that, 3 PC is about 10 LY]

  • Small Angle Formula: D   =   α d 206265

    D = linear distance (length of object perpendicular to line of sight)
    d = distance to object along line of sight
    α = angular size of object in arc seconds (1/60 of 1 minute of arc)

    Note: 206265 arcseconds = 57.296 ° = 1 radian

Web Lecture

Read the following weblecture before chat: Introduction to Astronomical Concepts and Methods

Study Activity

Planetarium program exercise

These tasks should be possible on any computer-based planetarium program. You will need to review the user guide for your program to identify exactly how to do each one.

  • Check the date and time on the display screen. By default, this should be the same as your system time, but you can control it (see below).
  • Use your location setting method to enter your latitude and longitude or find a city near you to use as your home location.
  • Use your date and time tools to advance the clock forward and backwards, or to run the display at a rate faster than normal time. When you have finished experimenting, set the time to 9pm for today's date.
  • Find and set your field of view size. In most cases, you can set this to 180°, 270°, or 360° around your horizon, and control the range above or below your horizone (-90° to +90°).
  • Find and set your horizon to display so that you can see the horizon line and the star field above and below it. Some programs default to a "solid" horizon, so you may need to set this. Turn on direction markings (N, E, S, W) so that you know which direction you are looking.
  • Turn on the planetary displays.
    For Tuesday night, Sept 11, 2018, here is something close to what you should be seeing:
    • Sky Safari at 9pm, for Seattle, WA, with horizon set to transparent and line:


    • Starry Night at 8:50, for Seattle, WA, with horizon set to transparent.


    Your sky may be different, depending on your location, but just before sunset, you should be able to see Mars just above the southern horizon, with Saturn fainter and to the right of it. Jupiter will be on the western horizon. If you go out about an hour earlier, you may be able to see Venus setting in the west; it should be quite easy to pick out despite the sun's glare.

  • Find the tool to enter a specific object's name. Type in "Vega" (the brightest star in Lyra) and have your display center on Vega. See if you can still find the planets in relation to this star and the constellation Lyra.
  • Using your program, determine what constellations will be rising (due east), on your meridian above the horizon (due south), and setting (due west) for some night within the next two weeks where you might be able do some observing.

Optional websites:

While astrology is NOT the subject of this course, astrological symbols are often used as a "shorthand" on astronomy charts, so it is work becomeing familiar with them.

Constellation symbols for those in the zodiac:
See the Wikipedia article on the Zodiac, and scroll down to thetable that matches the symbols with the constellation name. Although astronomers are not usually also astrologers, they use these signs as a shorthand on maps and when taking notes.

  • Check out the planetary symbols used by both astronomers and astrologers: these can be a useful shorthand when marking observing maps and charts.
    Planetary Symbols
  • Visit the Powers of 10 site to view the change in scale.
  • Visit the online planetarium at Fourmilab and enter your latitude and longitude (if you don't know them, you can use Lat-Long Finder to discover them), then click on "Make Sky Map". The planetarium will show you the sky for the current time.
    • Note that this is a map for you to use when facing south and looking up. North is at the top and south is at the bottom but east is on the left and west is on the right. Stars on the right are setting and stars on the left are rising. Planets to the right of the sun are "morning planets": the set before the sun sets and rise before the sun rises. To view them, you have to get up before dawn. Planets to the left of the sun are "evening planets" and will set after the sun least for a month or two, depending on the motion of the planet and the motion of the sun.
    • What constellations are visible?
    • Is the moon up? What phase is it in? What part of the sky is it in (east, west, overhead, not visible)
    • What planets are above the horizon? (use the symbols chart above to identify the planet!) What part of the sky are they in?
    • Notice that the time is showing as Universal time. Change it so that will show you the sky at 9pm at night for the day you do this exercise. For example, if it is now 7pm and the UT is 2:35:32, add 2 hours to the time, then click the "Update" button below the display. What happens to the locations of the moon and planets?
    • Select a visible planet and click on it. What constellation is it in?

Chat Preparation Activities

Chapter Quiz

Lab Work

Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.