Space Travel in the DOGULEAN Planetarium

You should probably work through the stargazing tutorial before trying this one.

To follow the tutorial, open another browser window and do what it suggests in that window.

Space travel adds just a few new capabilities to what you can do when Stargazing but the experience is remarkably different.

1. Get into space travel mode.

  1. Right-click the mouse to Open the Control Panel.
  2. Select Space Travel in the "Mode" drop menu at the top.
  3. We see that we now have a Home Planet, which is currently Earth. That is the planet we are on or near, and our position is relative to its position. We'll stay on Earth until the last part of this tutorial.
  4. Right click again to close the Control Panel.

2. Rolling; dragging in a straight line.

  1. Space travel is like flying a spacecraft, so we can do acrobatics that we can't do while standing on the ground. We can roll our spacecraft and we can fly in a loop.
  2. To roll your spacecraft over, hold down the left mouse button and drag the mouse along the bottom of the screen.
  3. If we drag elsewhere on the screen, it changes our direction of view, as in stargazing mode, but with some differences.
  4. First, if we put our mouse on some point in the sky and start dragging, the point will stay under our mouse. It may lag behind in the middle of a drag, but it will catch up when we stop. In Stargazing mode, it didn't quite happen that way.
  5. Second, the Earth may slant when we drag, especially if we drag horizontally. In Stargazing mode, the Planetarium makes adjustments to prevent this slant, and those same adjustments cause the point we are dragging to slowly move away from the mouse pointer.
  6. Straighten out the Earth and now drag down to look up. Keep doing that. The Planetarium does not stop us at the zenith. Eventually the Earth appears over our head. We are flying our spacecraft in a loop.

3. Ascending and descending.

  1. Continue flying in a loop by dragging down, until you don't see anything but the Earth.
  2. To ascend, you put the mouse pointer on your planet and turn the mouse wheel forward – as if we are pushing the planet away. Turn the mouse wheel backward to descend. That is like pulling the planet toward us.
  3. Ascending and descending are like zooming. When you ascend, your planet gets smaller, When you descend, it gets larger.
  4. Holding the mouse wheel down and dragging down is another way to ascend. Dragging up will descend.
  5. If you put the mouse pointer somewhere off your planet, turning the mouse wheel or holding it down and dragging vertically will zoom or unzoom, the same as in Stargazing mode.
Exercises:
  1. If you have an actual mouse with a mouse wheel, put the mouse on your planet, press the mouse wheel and drag up until the planet shrinks enough (you gain enough altitude) that the mouse is no longer over the planet.
  2. Without releasing the mouse wheel, drag back down so that you descend again and the planet gets larger.
  3. Now try turning the mouse wheel forward until the mouse is off the planet and then turning back.

4. Finding a lost planet.

  1. Once you are above your planet, it is rather easy to lose track of where it is, just by left-dragging to look around.
  2. If you do lose your planet, left-click the "Look Down" button at lower left.
  3. Your will be looking right at your planet. Let's descend again to the surface.

5. How to fly around your planet

  1. Adjust your altitude, by turning the mouse wheel forward, so you that you are off the surface of your planet. You don't need to be high, just off.
  2. With the mouse pointer on your planet, hold down the left mouse button and drag. Your direction of view will change (the planet will appear to move) until you can see the curved horizon. (If the horizon is not definitely curved, you are still on the surface of the planet. Increase your altitude a little.) Once you can see the horizon, your planet will appear to turn over in the direction in which you are dragging it.
  3. Actually you are flying around it. That is why the stars in the background appear to fly by.
  4. If you put the mouse pointer somewhere off your planet and drag, it still just changes your direction of view.
  5. So the primary function of left dragging is to change your direction of view. Left dragging on your planet will turn it over only if you are off the surface and can see enough non-planet space that you could drag there if you wanted.
Exercise:
  1. Reduce altitude until you are on the surface. If you are looking at the Earth, drag down until you see the horizon going straight across the screen, a bit below the "Real Time" button. If the horizon is curved, you are not on the surface – reduce altitude some more. You should see direction markings along the horizon, as in Stargazing mode.
  2. Try left-dragging on the Earth. It will just change your direction of view.
  3. Increase altitude by turning the mouse wheel forward until there is a change. Direction markings should disappear. Left-drag on the Earth now and it should appear to turn.

6. Fixed and Floating.

  1. Let's press the Look Down button and then ascend so that we can see all of our planet.
  2. Note that flying around the planet works even better from up here.
  3. In Space Travel mode, Date and Time work just as they do in Stargazing mode. I have to say with some regret that we always keep Earth time, even when we visit other planets.
  4. One way to get a good look at a planet should be to step through time so that as it rotates, we get to see all of it. But if we do step through time, we see that, although the dark part of the planet changes, but we remain above the same spot on the planet and we always see the same side of the planet.
  5. That is because our longitude is fixed and does not change, so we go around with the planet as it rotates.
  6. We can see the whole planet if we press the button at lower left that says "Fixed". It will change to "Floating".
  7. Now if we step through time, we will not go around with our planet – we will float above it and the planet will turn beneath us. As the planet turns, we will eventually see all of its surface. Our position in space near the planet is fixed instead of our longitude.
Exercise:
  • Set Floating and travel forward in time by months. The shadow on the Earth does move! Why?
  • Don't forget to set Fixed before continuing.

7. View Planet.

  1. Let's try out View Planet, which is still here at bottom right by viewing Jupiter.
  2. Zoom in so we can see Jupiter's bands. It is oriented up and down. In fact, when you view a planet in Space Travel mode, you roll so that its north pole points up on the screen.
  3. We can check that by rolling and then viewing Jupiter again.
  4. Zoom back down.
Exercises:
  • Rise high enough above your planet that you can easily see Jupiter. Track and View Jupiter. Then roll the view a bit. Zoom in so you can easily see where Jupiter's poles are pointing.
  • Step forward in time by months. Notice that:
    • Jupiter's north pole always points in the same direction.
    • Jupiter gets bigger and smaller. Why?
  • Step forward by monthss until Jupiter reaches its maximum size. Now step back two months and then go back to stepping forward, but by days. You can hold down the little "day up" button. What happens? Why?

8. Tracking the stars.

  1. Now, let's look at another feature of Space Travel, tracking.
  2. The "Tr:" button at lower right, is another menu, the tracking menu.
  3. If we open it, we see that there are three kinds of things on it.
    • "None", meaning don't track anything.
    • "Stars".
    • Things in our Solar System – Sun, Moon, and planets.
  4. Let's try "Stars". If we track the stars, then as time passes by, they all stay exactly they are on the screen. The Sun, Moon, and planets, including our home planet, will pass by, but the stars will not move.
  5. If we change our direction of view, that moves the stars, but after that they stay in their new positions.
Exercises:
  • Rise high enough above your planet that you can easily see Jupiter. Track and View Jupiter. Then roll the view a bit. Zoom in so you can easily see where Jupiter's poles are pointing.
  • Step forward in time by months. Notice that:
    • Jupiter's north pole always points in the same direction.
    • Jupiter gets bigger and smaller. Why?
  • Step forward by monthss until Jupiter reaches its maximum size. Now step back two months and then go back to stepping forward, but by days. You can hold down the little "day up" button. What happens? Why?

9. Tracking a planet.

  1. Switch to tracking Jupiter and View it so it is in the middle of the screen. Zoom in so we can see the bands again. Now, if we step forward through time, the Jupiter will stay put and will remain oriented up and down. Everything else will move.
  2. If we move Jupiter off center and roll it, it will stay in its new position and orientation as time passes. In fact, wherever it is, on or off screen, it will stay in that position, with the same orientation, while we are tracking it.
  3. Let's zoom back out and then look down so we can see the Earth, and maybe move it a bit off center. If you try to roll your home planet while tracking something, the planet will roll away in an odd way. Usually that just means that you were tracking something earlier and you have forgotten to turn tracking off. But is actually useful if the thing you are tracking is behind your planet and you want to move your planet out of the way.
  4. Let's turn off Tracking by setting it to "None" and press "Real Time".
Exercises:
  • Rise high enough above your planet that you can easily see Jupiter. Track and View Jupiter. Then roll the view a bit. Zoom in so you can easily see where Jupiter's poles are pointing.
  • Step forward in time by months. Notice that:
    • Jupiter's north pole always points in the same direction.
    • Jupiter gets bigger and smaller. Why?
  • Step forward by monthss until Jupiter reaches its maximum size. Now step back two months and then go back to stepping forward, but by days. You can hold down the little "day up" button. What happens? Why?

10. Changing planets.

  1. Finally, let's talk about real space travel – changing our home planet.
  2. Make sure Tracking is set to None and turn star labels on, if you need to. View the Sun.
  3. The button at lower right that says "H: Earth" is another menu that is saying that Earth is our current home planet.
  4. Open the home planet menu and select Mars. We see that the Sun and planets have moved and the lines have moved, but the stars are all exactly where they were.
  5. The lines change so that they show the Equator of our new home planet, its poles, and its ecliptic, indicating the plane of its orbit, not the Earth's orbit.
  6. CHANGE: On info bars of stars and planets, the right ascension and declination are now those appropriate to the current home planet.
  7. When you change planets, the planetarium puts you at the location on the new planet that has the same view of the sky. Your altitude, relative to the size of the planet, does not change, so the planet appears to be the same size.
  8. If you are not tracking anything or are tracking the stars, the Planetarium directs your view so the stars all appear in the exactly the same place as they did before you changed planets.
  9. If you are tracking a planet, you will go to the same point on your new home planet as if you were not tracking, but your view will be directed so the planet you are tracking is in the same position on or off screen and so that the planet's poles point in the same direction.
  10. Let's track and view Jupiter. Zoom in so we can see where its poles are, but not so much that we can't see the stars around it.
  11. Now, if we change planets, it is Jupiter that stays in the same place and it is the stars and other planets that move.
  12. Sometimes when you change planets, the planet you are tracking will end up on the other side of your home planet. If you want to see the thing you are tracking, you can either increase your altitude to shrink your new home planet or you can roll your new home planet out of the way.

11. Summary. Here is a list of the things that are new in Space Travel mode.

  1. Left-dragging along the bottom of the screen rolls your view.
  2. If you left-drag in the sky, the point in the sky where you start dragging will, allowing for lags, stay under your mouse. Your view may roll, usually not too much.
  3. There is no restriction on dragging past the zenith.
  4. Pressing "Look Down" will bring your planet to the center of the screen.
  5. If you mouse-over your planet:
    1. You can change your altitude by turning the mouse wheel or by holding the mouse wheel down and dragging vertically.
    2. If you are above the surface of your planet, left-dragging on your planet will make you fly around it. Your planet will look like it is turning over.
  6. There are two position types. Fixed, where you have a fixed longitude and go around with your planet as it rotates; and Floating where you float over your planet as it turns beneath you.
  7. You can change home planet using the "H:" menu at lower right.
  8. If you view a planet using the "V" menu at lower right, your view will roll so that the planet's north pole points up on the screen.
  9. If you track the stars or a planet using the "Tr" menu at lower right, they or it will stay at the same place on – or off – screen, with the same orientation, as time passes.
  10. And that completes our tutorial on Space Travel mode.