Celestia/Print Version

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This is the print version of Celestia

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This is an initial attempt to create a printable version of the Guide to Celestia. It is only a start. Don't even bother trying to print it just yet.


Celestia

The current, editable version of this book is available in Wikibooks, the open-content textbooks collection, at
http://en.wikibooks.org/wiki/Celestia

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License."

[edit] Celestia

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Celestia provides photo-realistic, real-time, three-dimensional viewing of the solar system, the galaxy and the universe. It is an easy to use, freely-distributed, multi-platform, open source, software package which has become a valuable tool for astronomy education. Used in homes, schools, museums and planetariums around the world, it also is used as a visualization tool by space mission designers. Versions are available for computers running Windows, Macintosh (MacOS X) and Linux operating systems.

Although it is optimized for 3D astronomical visualization, Celestia can be used to display and explore other 3D environments, too.

And, for some reason, many people seem to find exploring with Celestia to be a lot of fun.

[edit] About This Guide

This Guide to Celestia is intended to be a comprehensive source of information for students, educators, and other users of Celestia. It will include instructions for obtaining, installing, using, customizing, and troubleshooting the Celestia software, as well as explanations of concepts and techniques from astronomy and computer graphics as needed to fully explore and understand Celestia and its universe. It is intended to address the needs of novice, casual, and advanced users.

The Guide to Celestia is just beginning development and is very far from complete. You can help by adding useful content. Members of the Celestia community are encouraged to be bold in editing this WikiBook to provide the additions and corrections needed to make it useful for themselves and others. Please share your knowledge here.


Icons indicate approximate development status.
Of course, all pages are subject to improvement at any time.

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[edit] Using Celestia

How to use Celestia is described in detail in Frank Gregorio's Celestia 1.4.1 User's Guide.

[edit] Getting Celestia to Run

[edit] Exploring Celestia's Universe

[edit] Understanding Celestia

[edit] Enhancing Celestia

The following reference pages will help you to add features and make Celestia easier to use in your environment.

[edit] Scripting

[edit] Customizing Celestia

  • Specifying the Correct Time: TDB is not UTC

[edit] Troubleshooting

[edit] Development

[edit] Credits

[edit] External links

[edit] Related WikiBooks

[edit] Celestia Web Sites

[edit] Celestia Add-ons

[edit] Articles about Celestia

[edit] Why Celestia?

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[edit] Why would anyone want to use Celestia?

  • Because you have an interest in outer space and in the exploration of space.
  • Because it is Fun! That is, if you like to explore the Universe.
  • Because it is Educational. With Celestia, you can learn about the Universe.
  • If you are a teacher, you already have access to Frank Gregorio's Lesson Plans. These are designed to educate while they entertain bored young minds.
  • Because if you are an Artist, it gives you all the freedom necessary to develop your ideas...
  • If you don't have a telescope, you can still view the planets up close, and in person. You can also view their moons, orbiting spacecraft and a whole lot more.
  • Because it is absolutely free. No charges or fees of any kind ever.
  • Trajectory analysis?
  •  ?

[edit] Why not use some other program?

  • Freeware
    • Hayden Planetarium's Digital Universe Atlas
    • Jason Harris' KStars
    • 4D2U's Mitaka
    • Martin Schweiger's Orbiter
    • NCSA's Partiview
    • Stellarium
    • Clear Sky Institute's XEphem
  • Shareware
    • FMJ Software's StarStrider
  • Commercial
    • Software Bisque's Seeker
  •  ?

Although ALL of the above software titles are useful in their own right, none of these allow such thorough journeys to the planets, their moons, the stars, the asteroids, the galaxies and the planetary nebulae - ALL in one place. These visits are up-close and personal and in vivid detail with exceptional graphics and animations. You can also visit many, MANY spacecraft and see what they look(ed) like in space.

[edit] What Can't Celestia Do?

  • Telescope control
  • 180 degree field of view
  • Sound
  • Stereo viewing
  •  ?

[edit] Installation

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[edit] Introduction

Celestia can easily be installed on computers running Windows, MacOS or Linux. If you have the necessary experience, it also can be compiled and installed on computers running other operating systems.

The current version of Celestia is available by way of the download page on the Celestia Web site. The links on that page actually point to files in Celestia's repository on SourceForge.

Older versions of Celestia are also available from SourceForge.

Prereleases of the next version of Celestia are usually announced on the Celestia Web Forum in its Users Forum. They are not available on SourceForge.

[edit] Windows

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If you have downloaded the Windows version of the Celestia installation executable, then you simply need to run the .EXE file you downloaded. Windows XP is the preferred OS at the moment, but you can also setup Celestia in Windows Vista.

A few words of caution to Windows Vista users, however...

If you run the setup program as a Windows XP-compatible application, you'll find that the program runs fine and that Celestia operates as it should. You can also run the Celestia executable in the native Windows Vista mode too.

Savvy Windows XP users will find that their are a LOT of things to get used to in the XP-compatible mode though. If you modify a planet texture, for example, you may find that your modified texture was NOT saved to the Celestia program directory where you got it from originally.

Vista likes to create shortcuts to modified textures, and these - for some reason - aren't readily available to the Celestia program. If you're using Windows Explorer to view the Celestia texture files, click on the "Compatibility Files" area at the top of your screen to see your modified texture. If you like, you can then copy and/or move the new texture to the C:\Program Files\Celestia\textures directory of your choice.

[edit] MacOS

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[edit] Linux

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[edit] Building from sourcecode

See Celestia/Development

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[edit] Graphics Hardware

The text in its current form is incomplete.

[edit] Introduction

Celestia uses OpenGL graphics routines to draw its pictures of the universe. Unlike DirectX, which is available only on computers running Windows, OpenGL graphics libraries are available for many different types of operating systems. OpenGL was originally developed by SGI but now is available for use on almost all computers and graphics hardware. The OpenGL WikiBook has more details.

Celestia can run on most computers, but to see all of its "eye candy" a modern graphics card implementing OpenGL v2.0 is essential. Even when the best available graphic cards have been installed, some computers have problems running Celestia because their graphics drivers are out of date or buggy. Regularly check the Web site of the manufacturer of your computer or of your graphics card to make sure you have the current driver version. Updated drivers are provided often.

[edit] Graphics Card Limitations

Many graphics card limitations are described in Celestia's list of Frequently Asked Questions:

What graphics card should I get?

[edit] Operating System Limitations

Many computer and O/S limitations are described in Celestia's list of Frequently Asked Questions.

[edit] Linux

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[edit] Mac OS X

  • Graphics driver updates for Mac OS X are available in updates to Mac OS X itself, not in general as separate driver updates by NVIDIA or ATI. This means "upgrade your driver" on OS X means "make sure your version of OS X is up-to-date". You may have to spend money in order to get the current version of OS X.
  • Point sprite primitives do not work on versions of OS X earlier than 10.4.
  • Point sprites are not supported properly on Tiger (PPC and Intel architectures). Colors may appear incorrect, and hard freezes requiring a reset have been seen. VBO seems to be involved. Apple has been made aware that this is almost certainly a driver bug, but no fixes have been promised. Behavior on Leopard is unknown.
  • The OpenGL 2.0 render path is only supported on Tiger 10.4.3 or later, regardless of the graphics card.
  • Holes may appear in orbit paths on certain ATI configs. A workaround is being investigated. Fixed in 1.5.0.

[edit] Windows

  • The graphics drivers provided with your brand new computer hardware already are obsolete. Usually several months have passed between the time its software was configured and it was provided to you. Be sure to download and install the most recent graphics drivers provided on the Web site of the manufacturer of your computer's graphics hardware.
  • Windows XP includes a software-only OpenGL library. It's used on systems without 3D hardware or when hardware acceleration is disabled in the Display Control Panel. It implements only OpenGL v1.1, Celestia's Basic rendering path, so it has limited functionality and runs rather slowly, but it is relatively bug-free.
  • Celestia does not use DirectX, which is Microsoft's proprietary 3D graphics programming library. Unfortunately, whenever Microsoft's DirectX libraries are updated, the manufacturer's OpenGL drivers are replaced by obsolete versions provided by Microsoft. Whenever you update DirectX, be sure to reinstall the graphics drivers using the most recent versions provided by the manufacturer of your computer's graphics hardware.

[edit] Getting Started

The text in its current form is incomplete.

[edit] Introduction to using Celestia

To start Celestia, you should double-click on its icon. As it starts, it first shows the Sun, and then takes your viewpoint to the sunlit side of the Earth. When you get there, you can tell Celestia to show you other interesting sights.

Initially, Celestia opens in a window on your screen. For a more immersive experience, you can tell Celestia to take over the entire display. Open Celestia's menu Render/Select Display Mode and choose an appropriate screen resolution. When it's in full-screen mode, if you move the cursor up to the top of the screen, you should see Celestia's menu bar again, where you can choose to go back to windowed mode.

Some may think Celestia is a game. In a way it is but it is much more than that. Like most programs (with graphics and objects) of today the mouse is the primary way of getting around. Celestia does use the mouse to rotate/panned the observers POV with a combination of left and right mouse click and drag functions. However to truly get the most out of Celestia the keyboard shortcut letters bring the full power and beauty of the program into play. People who are more game enthusiasts may find the interface of Celestia boring after a few minutes if they only us the mouse. So, start learning and memorizing the keyboard shortcuts. You can find a quick look of the keyboard shortcut commands in the Help/Control pulldown while the program is running. You can also find them in the Celestia User's Guide.

Below are some introductory events and places you can explore in Celestia, using the keyboard and mouse. You will notice below some letters and words are in bold face. These are the keyboard shortcuts that can be typed to control Celestia.

[edit] Earth's rotation and the pole star

This needs a fairly wide field of view – use the comma (,) and dot (.) keys to adjust the window to around 60°. If you don't have the Earth on the screen, press the three keys H3G to go there. Then back away a little with the End key or your mouse's wheel. Adjust the number of stars with the [ and ] keys, setting a limiting magnitude of around 5.

Adjust the rate of time to 1000 times faster (LLL) so the Earth can be seen slowly turning. The Earth spinning is what gives us day and night. Type a "y" to hover over one point on the Earth and see it enter light and shadow (day and night) as the Earth turns. Use the arrow keys Shift-← and Shift-→ to move round the Earth and see where night and day start and end. You can put the mouse cursor over a piece of land and just watch that point as day and night pass over it. This is best done with the clouds turned off (I). To turn the "sync orbit" off again, you can press F to return to "follow" mode.

With the synchronous orbit on, back away from the Earth a little using the End key (or the rotary wheel of your mouse if it has one) so you can see more stars. You can press the Home key to move closer again. As you watch the stars go past, you might see distinctive patterns of stars go by. People used to imagine people and animals in the patterns in the stars. Press / to turn on the constellation lines, and = to turn on their names. You can use the space-bar to pause time and take a longer look at any interesting shapes.

With the mouse, right-click and drag upwards to turn to look more Northwards. By the time you are looking squarely at the South pole of the Earth, the pole star Polaris should be visible. It's the star that's at the end of the tail of Ursa Minor, the "Small Bear", often called "the Little Dipper". If you watch for a while, you will see that all stars seem to revolve around that point while Polaris itself doesn't move much at all.

Keeping this view, zoom closer to the Earth (Home) and notice the way day and night look on Earth from this view. Depending on the time of year, the Antarctic ice-cap might be on permanent daylight or permanent shadow. This can be easier to see if you speed up to 10000x (L). You can briefly speed up even more (use K to slow down again) to hop between seasons.

[edit] Other Planets

Start Celestia. You are looking at the Earth from the direction of the Sun. We want to look at the Earth from the other side. Back away from the Earth using the End key until the Earth is about the size of a pea, and then use Shift-← and Shift-→ to rotate around the Earth until the Sun is visible in the background. The Earth might be easier to see if you turn up the background illumination with the } key, although this is not realistic as it makes planets glow in the dark (only stars really do that). Now turn the time rate up to a million times faster by typing LLLLLL.

You should notice the Moon whizzing round the Earth. Move closer or further away (Home/End) until the moon uses the whole width of the screen. The Moon takes about 28 days to go round the Earth. If you slow down time a bit by pressing K, you should be able to count the number of days (turns of the Earth) it takes for the Moon to go round once. You can turn the Moon's name on and off by pressing M. If you see a giant mass of names appear, all together, it's probably the names of all Jupiter's moons in the distance – Jupiter has a lot of moons. Speed back up to a million times again.

You will notice that every year as the Sun goes past, it is accompanied by a collection of small bright dots. These are other planets. You can turn their names on and off with P. It's time to leave the Earth. Type HFC to follow and centre the Sun. Leave planet names on (P). Back away from the Sun a little and you will be able to see Mercury, Venus, Earth and Mars moving from side to side as they orbit the Sun. If you back away further you will be able to see 9 planets. The outer ones don't seem to be moving much, so press L speed things up a little. Time is passing at about a year every 4 seconds now.

Let's turn on the planet's orbit lines – press O. They're not very clear seen edge on, so use the right mouse button to drag downwards until the orbits look circular, seen from above. You can't see all the orbit lines at once – if you move far enough away to get Pluto's orbit in, then the inner planet's orbits disappear. Move in to see the inner planet's orbits and the outer orbits are off the screen. By right-dragging, you can get a good edge-on view that shows that all the orbits are in almost exactly the same plane except for Pluto.

You may notice as Jupiter goes past that it has a huge mass of orbit lines for its many moons. Four of them are big enough to be seen from the Earth by using binoculars.

Time for a quick tour. This is possible best done with the orbit lines switched on. First, to about 1000x time rate (K,L). Then we can visit the 9 planets by typing 1G, 2G etc. Each of the number keys corresponds to a planet. Use Home and End (or the mouse scroll wheel) to zoom in and out, and right-drag to change the viewpoint and get a good look at each planet.

While visiting the outer planets, it is worth looking from above to see just how much like a little solar-system their moons make. You may occasionally see a black spot move across the sunlit surface of Jupiter – this is the shadow of one of the moons as it passes between Jupiter and the Sun.

[edit] Other Stars

Not all stars are like the Sun. Some stars are hotter than the sun, some cooler, bigger, smaller, brighter and dimmer, redder, bluer. Actually the blue ones are hotter, and the red ones cooler.

You cannot tell how far away stars are by just looking at them. So when people invented the constellations, they drew lines using stars that might be nearby, or far away. A good demonstration of this is to see how distorted familiar constellations would look if seen from a different angle – from a different place.

Turn on the constellation lines (/) and use dot and comma to set the field of view to around 60°. Centre a star in the constellation of the plough (Ursa Major, also called the Big Dipper) by pressing the Enter (↵)key, typing the name megrez and enter again. Then type CF to centre and follow the star. Now hold down the right mouse key and drag around the screen. Your viewpoint is now many light years away from the Earth, orbiting around the distant star Megrez. Try both with and without the constellation lines. You can plainly see the 3D pattern of the stars. If you move right round the back of the Plough (or Big Dipper), you can see that all the constellation lines seem to point roughly in the same direction – the direction of Earth.

It is interesting to return to the Sun while maintaining your view on Megrez – press T to track Megrez (keep it centred), then HG to go home. You can see the constellations return to their familiar shapes as we get back to the Sun. Press T again (or Esc) to stop tracking Megrez.

Another good star to do this with is Arcturus in the constellation of Boötes.

The constellations are all drawn with stars that are visible from the Earth, and are therefore the nearest stars to us. Turn the constellation lines on and then back a long way away (hold End), until all the lines are visible on the screen. Turn on more stars by holding the ] key and raise the limiting magnitude to about 10. Back away a little more until the whole of the galaxy is visible on the screen. Then right-drag so the galaxy is seen edge-on. You can see that the stars in the Celestia program form a sphere round the Sun. This is because we don't know the distances of all the other stars in the galaxy well enough to put their positions in the program – so the rest of the galaxy is just shown as a 'mist' of stars.

Reduce the limiting magnitude to 10 or less again with the [ key.

[edit] Other Galaxies

You can fly to another galaxy much like our own by pressing ↵m 31↵g. You can always go home again by typing the keys H3G.

[edit] Celestia's Command Line

The text in its current form is incomplete.

[edit] Introduction

Celestia can be started either by clicking on its icon or by typing a command into a terminal window. Under Windows, the terminal window is often called a DOS window or CMD window.

A typical command to run Celestia might be

cd Celestia
./Celestia

The command line can optionally include the following qualifiers. These qualifiers are different depending on which command interface Celestia was built for. Each command qualifier (aka switch) should be prefixed by two hyphens

[edit] Windows command qualifiers

  • --dir <path>
Change root celestia directory to <path>
  • --fullscreen
Start Celestia in fullscreen mode
  • --once
Send the command line to a running instance of Celestia. If no running instance exists, a new one is started.
  • --url <url>|<filename>
Start in the given <url> or if the parameter is the name of a script file, execute <filename>.
  • --verbose >    <filename>
Write debug messages to <filename> (Although --verbose can only write to a file, the redirection > is required.)

[edit] gtk command qualifiers

  • --conf
Use alternate configuration file
  • --dir
Use alternate installation directory
  • --extrasdir
Use additional "extras" directory
  • --fullscreen
Start full-screen
  • --nosplash
Disable splash screen
  • - v [0|1]
Enable debug mode.

[edit] KDE command qualifiers

  • --conf
Use alternate configuration file
  • --dir
Use alternate installation directory
  • --extrasdir
Use additional "extras" directory
  • --fullscreen
Start full-screen
  • --nosplash
Disable splash screen
  • +[url]
Start and goto URL
  • <url>
Start in the given url/execute script file.
  • - - help
Command-line help

[edit] Locations

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[edit] Introduction

Celestia includes several catalogs of Locations on the Earth and on objects elsewhere in the Solar System. They're short, only containing lists of major features, like the Earth's oceans, continents and capital cities of nations. More extensive catalogs of Locations are available as Addons.

Locations are labeled positions, usually on the surfaces of objects defined in SSC catalog files. They're shown if you select the option "Label Features" in the menu Render / Locations...

When Locations are enabled, you can use Celestia's goto functions to travel to them.

[edit] Navigation

[edit] Mouse and Keyboard Controls Used for Navigation in Celestia

[edit] Mouse Functions:

Celestia works best with a three-button wheel-mouse. Very inexpensive ones are available which work well with Linux, Mac and Windows computers.


Left drag: Orient the view.

Right drag: Orbit the selected object.

Wheel: Adjust the distance to your current selection.

Right + Left drag: Adjust your distance to the selection.

Ctrl + Left drag: Adjust your distance to the selection.

Shift + Left drag: Changes your field of view (e.g. => Telescopic view.)

Wheel click: Toggles the field of view between 45 degrees and the previous field of view.

Left - click: Select the object you click on.

Left double click: Center the selection.

Right - click: Brings up the context menu.

[edit] Keyboard Navigation Commands:

H  : Select the sun. (Home.)

C  : Center on the currently selected object.

G  : Go to the currently selected object.

F  : Follow the selected object.

Y  : Orbit the selected object at a rate synchronized to its rotation.

:  : Lock on the selected object.

"  : Chase the selected object. (The orientation is based on the selected object's velocity.)

T  : Track the currently selected object. (Keep the selected object centered in the view.)

HOME : Move closer to the currently selected object.

*  : Look back. Causes the view to shift from objects forward in the direction of motion, to objects rearward.

END  : Move farther from the selected object.

ESC  : Cancel the currently executing motion or script.

Shift+C  : Center/orbit. (Center the selected object without changing the position of the reference object.)

Left : Move (or roll) the camera view left.

Right: Move (or roll) the camera view right.

Up  : Move (or pitch) the camera view up.

Down : Move (or pitch) the camera view down.

Shift+ Arrow: Orbit the currently selected object in the direction indicated by the arrow selected.

1-9  : Select any of the planets orbiting our Sun. (2=Venus, 4=Mars, etc.)

ENTER  : Select a star or planet by typing its name.

Ctrl+C, or Ctrl+INS  : Copy location URL to your clipboard.

[edit] Spaceflight:

F1 : Stop.

F2 : Set velocity to 1 km/s.

F3 : Set velocity to 1,000 km/s.

F4 : Set velocity to speed of light.

F5 : Set velocity to 10x the speed of light.

F6 : Set velocity to 1 AU/s.

F7 : Set velocity to 1 ly/s.

A  : Increase velocity.

Z  : Decrease velocity.

Q  : Reverse direction.

X  : Set movement direction toward center of screen.

[edit] Number pad:

4  : Yaw left.

6  : Yaw right.

8  : Pitch down.

2  : Pitch up.

7  : Roll left.

9  : Roll right.

5  : Stop rotation.

[edit] Joystick Controls:

X axis  : Yaw.

Y axis  : Pitch.

L trigger : Roll left.

R trigger : Roll right.

Button 1  : Slower.

Button 2  : Faster.

[edit] View Control

The text in its current form is incomplete.

[edit] Introduction

Celestia provides you with very powerful and flexible ways to control your view into Celestia's simulation of the cosmos. Once you understand how to manipulate its interactive controls, you can quickly and easily position yourself to view the astronomical phenomena that interest you. If is helpful to think of Celestia as providing a remotely-controlled camera that is at your command. The view that you see on your screen is determined by the location of the camera, the direction the camera is pointing, and the magnification of the camera's zoom lens. Each of these factors can be controlled independently.

One important thing to understand is that both the location and direction of the camera are specified relative to some frame of reference. The frame of reference may be attached to a moving object (such as a planet or moon). If so, then the actual location and direction of the camera (with respect to absolute space) will automatically change as the object moves. This is often very convenient, because it means that you do not have to continuously change the camera location and direction manually in order to keep the object in view.

Commands which change Celestia's view of the universe are described in the file Celestia/controls.txt

[edit] Zoom Control

The magnification of the camera's zoom lens determines how large or small objects will appear on your screen, and also how much of the environment around you is visible (the field of view). If you increase the magnification then objects will appear larger, but you'll have a smaller area in view. (You can also make objects appear larger by moving the camera closer to them. The difference between zooming and moving the camera is important, as we will explain below.) Celestia displays the current magnification factor and field of view in the lower right hand corner of the window. As you zoom in, the magnification factor will increase, and the field of view will decrease. Zooming out has the opposite effect. If you zoom out to a very large field of view, the view will become distorted, much like what you would see with a fish-eye lens.

Repeatedly typing a comma (,) narrows the field of view, increasing the magnification. Repeatedly typing a period (.) widens the field of view, decreasing the magnification.

[edit] Time Control

The text in its current form is incomplete.

There are several keys that can be used to control the rate and direction of the passage of time.


[edit] Table of keys

Key

Effect
J Reverse time
K Increase rate by 10x
Shift+K Increase rate by 2x (new in version 1.5.0)
L Decrease rate by 10x
Shift+L Decrease rate by 2x (new in version 1.5.0)
Space Stop time
 ! Set time to the computer's current time
 ? Display travel time for light between observer and selected object
- Subtract the above light travel time from Celestia's current time
\ Set time to real time

[edit] Bookmarks

The text in its current form is incomplete.

A Cel: URL is a bookmark that saves the time, location, rendering options and other settings of a specific Celestia event or place. These URLs can be exported and published as regular HTML, so that any Celestia user can share a Celestia scene with any other.

The Windows version of Celestia includes a Bookmark menu. Those bookmarks are not the same as Cel: URLs.

To record a Cel: URL to your computer's "clipboard", type a Ctrl-C, or the usual "copy selected region" keyboard shortcut. On a Windows system, you can type a Ctrl-Insert.

To paste a Cel: URL into a document, type a Ctrl-V, or the usual "paste clipboard".

[edit] Display Options

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[edit] Introduction

When Celestia starts, by default it shows a 3D image in a window on the computer's main screen. Depending on its user interface, Celestia may be able to occupy the entire screen.

Image quality can be improved somewhat, too.


[edit] Size

[edit] Linux

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[edit] Mac OS X

Celestia starts in a window whose position and size are saved. Enter/exit fullscreen mode by typing Cmd(Apple)+F. Move your mouse to the top of the screen when in fullscreen mode to access the menu bar.

Right-clicking (control-clicking) on objects to bring up a context menu, switching to other applications, hide, and opening panels like Preferences and Help continue to work 100% in full screen mode. Multiple screens should be detected properly, although when switching to fullscreen mode Celestia currently only targets the screen which is most covered by the Celestia window.

Various display options can be accessed from Celestia > Preferences or the Display menu.

[edit] Windows XP

Celestia starts in a window which is located in the same place and at the same size as when Celestia previously exited. The menu "Render / Select display mode..." provides access to the list of full-screen resolutions claimed to be supported by the graphics display.


[edit] Edges

By default, Celestia does not enable anti-aliasing. This means that you'll see stair-step jaggies and moving dots on the edges of objects, especially on diagonal lines. Turning on anti-aliasing will make the display run more slowly, but objects will look better.

Celestia includes two different anti-aliasing options: a menu and keyboard option to smooth the orbital path lines, and a configuration file option to enable full-screen anti-aliasing.

You can separately enable various levels of full-screen antialiasing in the controls for your graphics hardware. This will affect all 3D programs, not just Celestia.

[edit] Menu and keyboard (orbit smoothing)

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The Windows menu option Render/Antialiasing turns on hardware smoothing of the orbital path lines.

(What are the corresponding Linux, and MacOS menu options?)

The keyboard command Ctrl-X is available in all versions of Celestia to toggle this display rendering option.

[edit] celestia.cfg (full screen)

To enable full-screen antialiasing within Celestia, edit the file celestia.cfg. Find the line which currently says

# AntialiasingSamples 4

and delete the #. If your graphics hardware supports higher levels of antialiasing, you can increase its value appropriately. This feature will work only if your graphics hardware has been configured to allow application control of antialiasing.

[edit] hardware control panel (full screen)

Alternatively, you can open the software control panel for your graphics hardware and turn on its antialiasing features permanently. This will affect all 3D programs, not just Celestia.

In either case, while the edges of objects will look much better, Celestia will run more slowly. The framerate reduction will depend on the quality of your graphics hardware.

[edit] Render Paths

The text in its current form is incomplete.

[edit] Introduction

A Render path is Celestia's way of classifying graphics capabilities. Its different Render paths correspond to different sets of OpenGL functions.

Not all render paths may be available on your computer. A render path will be available only if your computer's graphics software includes the OpenGL functions that it uses. More sophisticated render paths require more recent graphics hardware, but not the most expensive version of a card.

When it is first started, Celestia automatically selects the best render path based on the graphics capabilities advertised by the computer's OpenGL library. However, you can interactively select any available render path. Celestia remembers which path you selected last and will use it when the program is restarted. Choosing another render path may be necessary if there are problems due to bugs in your computer's graphics drivers.

To select an alternate render path, type a Ctrl-V. That is, press the "V" key while holding down the "control" key. This causes Celestia to switch to the next available render path. The name of the newly selected render path will be shown briefly in the lower left hand part of Celestia's window.

[edit] Render Paths under Linux

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[edit] Render Paths under MacOS X

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[edit] Render Paths under Windows

Some of the render paths available on computers running Windows XP are

  • Basic
  • Multitexture
  • OpenGL Vertex Program
  • OpenGL Vertex Program/Nvidia combiners (only on Nvidia graphics cards)
  • OpenGL 2.0

Celestia can show more and improved "eye candy" when using the later render paths:

  • Basic requires OpenGL v1.1.
It shows the fewest effects. It's available even on systems which have only Microsoft's software support for OpenGL and have no 3D hardware acceleration.
  • Multitexture requires OpenGL v1.2.
It adds NightLights and the shadow of a planet on its rings.
  • OpenGL Vertex Program requires OpenGL v1.4.
It adds specular highlights on oceans, shaded mountainsides and the shadows of rings on a planet.
  • Nvidia Combiners adds a rudimentary haze effect.
  • OpenGL 2.0 requires OpenGL v2.0.
It improves the edges of eclipse and ring shadows, draws the shadows cast by as many as four separate light sources, and adds sophisticated atmospheric effects, including cloud shadows on the ground. Haze can be drawn, too, based on Mie and Rayleigh scattering functions. (These scattering functions are available only with Celestia v1.5.0 or later.)

[edit] OpenGL Versions

To find out what version of OpenGL the graphics drivers on your computer claim to support, select Celestia's Help menu. The entry "OpenGL Info..." will list details about your computer's graphics hardware and software.

[edit] Snapshots and Movies

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[edit] Introduction

Under some operating systems, Celestia can create a snapshot, recording its current on-screen display to a file. It also may be able to create a video recording of a sequence of frames while it is running. Other operating systems may require an external screengrab or video recording program.

[edit] Linux

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[edit] MacOS X

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Screenshots and movie recording have not yet been implemented in the osX version of Celestia. For the moment you can use system commands to take some screenshots.

Some people have reported that CaptureMe does a reasonable job of recording movies.

[edit] Windows

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When running the Windows version of Celestia, both snapshots and movies can be created:

  • Select the menu option "File/Cature Image..." or type the <F10> key to record a snapshot of the current view.
  • Select the menu option "File/Cature Movie..." or type <Shift-F10> to start recording a movie of what Celestia is showing.

[edit] FAQs: Frequently Asked Questions

The text in its current form is incomplete.

[edit] What is Celestia?

Celestia is a freely-distributed, multi-platform, open source software package that provides photo-realistic, real-time, three-dimensional viewing of the solar system, the galaxy and the universe. It has proved a valuable tool for astronomy education, and is used in homes, schools, museums and planetariums around the world. Versions are available for Windows, Macintosh (MacOS X) and Linux computers.

[edit] Where can I get more information about Celestia?

The Celestia Website has some additional information about Celestia.

The Celestia Forum is a good place to look for or ask for additional information. You'll find lots of friendly people there.

The Celestia Motherlode has many Celestia resources.

[edit] Where can I get the most recent version of Celestia?

You can download the latest version of Celestia (v1.4.1) from SourceForge.

Prerelease versions are announced in the Celestia Web Forum in its Users Forum.

[edit] What changes have been made to Celestia since the last version?

The developers maintain a list of all new functionality and bug fixes in the Celestia ChangeLog, which is located at SourceForge (most recent changes listed at bottom).

[edit] Questions about how Celestia works

[edit] Celestia crashes, what it draws is messed up or it's extremely slow. What can I do?

Celestia makes use of the most advanced features of OpenGL that your computer's graphics driver claims to support. Many older OpenGL implementations have serious bugs. Here are some options for improving Celestia's display, with the most likely ones first:

  1. Make sure full hardware acceleration is enabled in your display properties.
  2. Upgrade to the most recent drivers for your graphics card. Download them for free from the Web site of the manufacturer of your card, not from Microsoft.

Nvidia drivers can be downloaded from http://www.nvidia.com/content/drivers/drivers.asp

ATI drivers can be downloaded from http://ati.amd.com/support/driver.html

Notes:

  1. Graphics chipsets integrated into laptop systems usually require drivers provided by the manufacturer of the laptop itself. Too often proprietary "glue chips" prevent the chip vendor's drivers from working properly.
  2. Reduce or disable hardware acceleration to verify that the problem is hardware related.

[edit] Windows XP

  1. Whenever you upgrade Microsoft's DirectX software, you must upgrade or reinstall the graphics hardware manufacturer's graphics drivers afterward. Installing DirectX installs Microsoft's copies of the drivers, which usually are several generations old.
  2. To disable hardware acceleration under Windows, open the "Display Properties" window. Select the "Settings/Advanced/Troubleshoot" tab. (not the "Troubleshoot..." button). Move the "Hardware acceleration" slider all the way to the left. Click on the "OK" buttons to change the settings in use. This will cause Windows to use Microsoft's Generic OpenGL v1.1 library, which is limited, but seems to have relatively few bugs. It does everything in software, works on 2D displays, and is quite slow.
  3. Driver Upgrade Procedure
    1. download driver installation program
    2. use the Control Panel / Add or Remove Programs menu to delete the current graphics drivers.
    3. Reboot
    4. Cancel out of XP's offer to install new drivers.
    5. Run the Installation program for the new drivers.
    6. Reboot
    7. Configure desktop resolution and other desirable features.
The two reboots are essential in order to cause the old low-level drivers to be deleted. Without those reboots, the old low-level drivers will not be deleted and the new installation will not work properly, although it may not generate any error messages.

[edit] MacOS X

For Apple PPC and Intel computers running MacOS X, you must upgrade to the most recent version of the operating system. Updated drivers usually are not available separately.

Apple's OpenGL on MacOS X often has serious bugs which sometimes are not fixed in the most recent release of MacOS. You must report those problems to Apple, otherwise they will not get fixed.

[edit] Linux

For computers running Linux, you usually can download the drivers for free from the Web site of the manufacturer of your graphics card.

ATI's fglrx drivers for Linux often have serious bugs. Try to use the driver shipped with the most recent version of Xorg's X server software.

[edit] Celestia draws the Moon in shades of purple, blue and red. Why is it doing that and what can I do?

Your graphics chipset and its drivers aren't drawing bumpmaps and normalmaps properly: their OpenGL routine "GL_ARB_vertex_program" is defective. (This is often seen with the newer Intel graphics chips.) Assuming you've already installed the most recent drivers,

  1. Download and install a different version of Celestia. The program is frequently revised.
  2. Turn off some of Celestia's advanced display features.
    1. Type a [Ctrl-V] several times to select "Basic" or "Multitexture" render paths instead of the OpenGL Vertex programs. This disables the use of vertex and shading programs temporarily. If this does improve things after you've followed the previous suggestions, then you need to do the next step:
    2. Tell Celestia to ignore specific features that your OpenGL library claims (falsely) to support. To do this, edit celestia.cfg. Remove the # that's in front of the line
IgnoreGLExtensions [ "GL_ARB_vertex_program" ]
Celestia's Help menu lists all of the routines in your system's OpenGL library. Add equivalent Ignore lines for other suspicious routines.


Addendum provided Tech Sgt. Chen:

Shut down all background programs on your system before running Celestia (i.e., antivirus software, multimedia software such as REAL Player, Musicmatch, etc.) Graphics programs are notorious for consuming system resources and even the best of graphics cards are better off without competing for those resources.

[edit] Celestia still crashes, draws funny stuff or is extremely slow. What can I do?

Report the exact circumstances and details of your hardware and software in the "Celestia Bugs" forum. Celestia runs on many different hardware and software configurations. It is not appropriate to ask people to guess what you have. For example:

Problem: Celestia crashes when I look at Saturn with Ring Shadows enabled 
System: 256MB 1GHz Pentium 4, Windows 98 2nd ed 
Graphics: 128MB Radeon 9700, Catalyst 3.2, OpenGL v1.3.9088 
Program: Celestia v1.3.0

Hopefully you know the System information. If you're running Windows, System details usually are available in the Control Panel's System Properties menu.

Some of the Graphics information can be found in Celestia's Help menu. If you're running Windows, more details can be found in the Control Panel's Display Properties menu.

[edit] Where can I get another version of Celestia that might work better?

Older versions of Celestia are available on SourceForge v1.2.4 is extremely robust, but does not include many recent features.

"Prerelease" versions of Celestia for Windows often are available on Shatters.net. Look in http://www.shatters.net/celestia/files/ and http://www.shatters.net/~claurel/celestia/files/ The most recent "prerelease" (e.g. V1.5.0pre3 or later) may work for you, but may be even worse.

[edit] I want to see all possible Celestia eye candy. What kind of graphics card should I get?