Stargazing in the DOGULEAN Planetarium

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The description assumes a three-button mouse. If you have some other pointing device and are in doubt, see Pointing Devices.

Click on any highlighted text to play the video starting there.

1. The first time you use the Planetarium.

  1. Go to dogulean.com
  2. Press "Enter the Planetarium", the button at top center.
  3. If your browser asks whether to allow the planetarium to access your location, you should allow it, though you don't have to. The Planetarium will not send the information off of your computer. The Planetarium does not use cookies – it uses your browser's local storage to store its current settings, and that is all it stores.
  4. If you accept, then after a few moments, the planetarium will set your location. Now the planetarium will show you the sky as it is, where you are, now.
  5. If you don't want to let the Planetarium access your location, or if you don't have geolocation, or GPS, services, see "Setting your location manually", below.

2. Setting your location manually.

  1. Click the right mouse button to open the control panel.
  2. Click the left mouse button on "Viewer Location".
  3. Set the latitude and longitude you want using the sliders or number inputs. You can find your approximate longitude and latitude by finding the nearest town in a map application or by Googling it.
  4. You might do this because you can't use Geolocation or don't want to.
  5. Or you might set a location in the southern hemisphere if you live in the north, just to see what the sky looks like from there.
  6. If you set a position different from where you are and want to go back home, then, if you allowed the planetarium to know your position, you can left-click "Set from Geolocation". Otherwise you will have to set your real position manually.
  7. Close "Viewer Location" by left-clicking on it again.
  8. Close the control panel by right-clicking again or by pressing "Dismiss".
  9. The Planetarium remembers settings, including location from one session to the next.

3. Looking Around.

  1. Now let's learn to look around in the sky – that means, to change the direction we are looking, which I will call our direction of view.
  2. All you need to do is hold down the left mouse button and drag the mouse.
  3. If you drag horizontally, it is like turning around on the spot. If you drag vertically, it is like looking up or down.
  4. There is one trick: You are only allowed to look up as far as the point directly overhead, which is called the Zenith.
  5. If you want to look further that way, turn around by dragging horizontally and then look down on the other side.
  6. That is part of how the Planetarium makes sure that the Earth is always level and under your feet.
  7. You may also notice that when you drag in a straight line, the sky doesn't exactly move in a straight line. That is the other part of how the Planetarium keeps the earth level. I will discuss that more in the Space Travel tutorial.

4. Star and Planet Labels.

  1. Now that we know how to look around, let's find out what we are looking at.
  2. You can turn on star and planet labels by double-clicking the left mouse button.
  3. CHANGE: There are three label settings now – All Labels, Planets Only, and None (Labels Off). Double-clicking cycles through them. We will keep labels on for now.
  4. Constellations are color-coded. Each constellation has a label and all nearby stars with a label of the same color belong to that constellation.
  5. This constellation is Pegasus, the winged horse, and all these stars belong to it.
  6. A star label consists of a designator and possibly a name, if the star's name is well-known.
  7. There are several kinds of designators, but, for brighter stars, the designators are usually Greek letters.
  8. It is worth learning at least the first few Greek letters because usually, though not always, the order of the letters gives the order of brightness of the stars in the constellation.
  9. So: Alpha α, beta β, gamma γ, delta δ, epsilon ε.
  10. Planet labels are all green – a different shade of green from one we use for star labels. They just give the name of the planet.
  11. If you don't see any planets right now, don't worry about it. We will learn how to find them later.
Note: The Greek letters were assigned by Johan Bayer, a German Astronomer, in 1603, not by the ancient Greeks.

5. Changing Star Label Colors.

  1. If you have trouble distinguishing constellations with our default star label colors, you can try an alternate color scheme.
  2. Right click to open the control panel. Left click on "Screen Decorations" to open that section.
  3. On the "Label Colors" drop menu, you have a choice of two color schemes. Choose whichever you prefer. I usually use the default "Equally Spaced" scheme, but will use Alternate for these tutorial videos.
  4. Close "Screen Decorations" by left-clicking on it and close the Control Panel by right-clicking anywhere.

6. Star and Planet Info Bars.

  1. If you put the mouse over a star or a planet, an information bar will appear. Info bars will appear whether or not labels are visible.
  2. For a star, the info bar contains:
    • The star's designator.
    • The star's constellation, in a form that means "of that constellation". For example, "Pegasi" means "of Pegasus".
    • The star's name, if it has one. If the name is less well known, it will not appear in the label but will still appear in the info bar.
    • This one is Markab, Arabic for "the saddle", on Pegasus, the Winged Horse.
    • Next, there is the star's position in the sky, given as Right Ascension (RA) and Declination (D). Those are sky versions of longitude and latitude. These are called Equatorial Coordinates and I will explain them further in the "Lines" segment.
    • The star's Magnitude. Magnitude is a number indicating how bright the star is. The smaller the number, the brighter the star. Magnitude can be zero or negative.
  3. Planet info bars contain the planet's name, the Equatorial Coordinates showing where it appears to be in the sky, and its distance from the viewer in Astronomical Units (abbreviated AU).
  4. An astronomical unit is the average distance of the Earth from the Sun, about 93 million miles or 150 million kilometers.
  5. A planet's label will appear even if the planet is not visible, like Uranus here. (What you see here, is not Uranus, but a star in the constellation Aquarius.) If you put the mouse pointer near where the planet is, its info bar will appear.
  6. The planet will always be near one end or the other of its label.
  7. An info bar may disappear after three seconds – that is still a work in progress and I have turned it off for this tutorial. If an info bar disappears and you want it back, move the mouse off the object and then back on.

7. Zooming in – making the sky bigger.

  1. Now let's learn how to take a closer look at the sky, or rather, to make things in the sky look bigger. We call that zooming in. It is like using a variable-power telescope.
  2. There are two ways to do it.
    • Turn the mouse wheel toward you to make things bigger or away from you to make things smaller. Once we get back to the size at which we started, we are at zoom 1. We can't make things any smaller than that.
    • If you have a mouse wheel that you can press, like a third mouse button, hold it down and drag up to make things bigger or down to make things smaller.
    The first way, turning the mouse wheel, will also work with touchpads and mice that don't have obvious buttons.
  3. You may have noticed that a lot of stars don't have labels. As you zoom in, more labels will appear until all stars have them.
  4. Zoom back out before going on.
Exercises:
  • Move a planet you can't see, Uranus, Neptune, or possibly Mercury, to the middle of the screen and zoom in until you can see it. (Don't forget to zoom back out.)
  • A star whose greek letter has a number attached to it is a member of a group. Look around for such stars look at their info bars. If the infobar lists two stars with the same Greek letter, you have found a double star with both members in the Planetarium. Zoom in until the other star's label appears and you can see both members distinctly. (The Planetarium currently includes only stars with maginitude at most 5, so it may not include the dimmer member of a star pair.)

8. Lines.

  1. So far in this tutorial, we have been ignoring the purple, gold, and grey lines that the Planetarium draws on the sky.
  2. This purple line that goes around the sky at an angle to all the others is the Ecliptic. It indicates the plane of the Earth's orbit.
    • The Sun is always right on the Ecliptic.
    • The moon and planets are always near it.
    • The constellations of the zodiac are all along it.
  3. This gold line is the equator of the sky. It is always directly above the Earth's equator.
  4. This other gold line, at right angles to the equator is the line of right ascension 180°. Once a day, it is over the line of longitude 180° on the Earth, and at that moment, every star is directly above a point on Earth whose longitude and latitude are the same as the star's right ascension and declination.
  5. The line of right ascension 0°, on the other side of the Earth, is also gold.
  6. This point, where the purple line and the two gold lines cross, is called the autumnal equinox. When the Sun reaches that point, fall will begin in the northern hemisphere.
  7. The curved grey lines that are not quite parallel to the equator are lines of declination. They are 10° apart.
  8. The other lines, straight and not quite parallel to the line of Right Ascension 180°, are lines of Right Ascension. They are 15° apart. That is how far the Earth turns in one hour.
  9. The "Lines" button at the bottom left of the screen, turns the lines off or on. Usually I keep them on to give a sense of orientation and scale.

9. Viewing a planet.

  1. At the bottom right of the screen is the "View Planet" button. It is really a menu. If you choose a planet on it, say Venus, we will look directly at that planet's position, which means that the planet will appear right in the middle of the screen.
  2. If we view a planet that is not currently in the sky, say Mars, we will end up looking at its position, but through the Earth.
  3. Going back to view Venus again, and bringing up its info bar, we see that the Venus's coordinates are almost the same as the ones at the upper right of the screen. In fact, right after we selected "View Venus", they were exactly the same. The coordinates at upper right are those of the point at the center of the screen, but that point keeps changing as the Earth turns.

10. Date and time.

  1. At the top left of the screen there are controls for Planetarium date and time.
  2. By default date and time are given for the timezone you have set on your computer – local time. We have year, month, day of the month, hour, and minute.
  3. You can change one of the time components by putting the mouse over it clicking one of the little buttons that will appear. Or you can press and hold the little button to make things happen faster.
  4. You can also type numbers in the boxes. That makes sense mainly for the year, because for other components, the Planetarium makes a lot of automatic adjustments to keep the values in the right range.
  5. If you type something wrong, you can type something else, or get back to something sensible by pressing "Real Time". That sets the date and time back to Now.
  6. If you want to view a star, planet, or constellation that can sometimes be seen from your location, but just isn't in the sky now, changing time is usually the best way to find it.
  7. For example, let's try to view the moon. Since we are looking through the Earth toward the east, we know it is not up yet, so step forward an hour and a bit and we have a good view of it.
  8. You can also step through time to in order to watch something in "quick time" that really happens slowly. For example, if we view the Sun, we can step forward a day at a time to watch it move along the ecliptic.
  9. That completes this tutorial on Stargazing. Try the exercises and then explore on your own.