Celestia Users FAQ

[Guckytos]

Here are the updated FAQs for Celestia.

Graphics

1. The Earth and other planets look strange. They have weird colors or do not look like globes. How can I fix this?
2. Celestia is drawing planets and moons bright red. Why?
3. The Moon is purple, blue and red. Why?
4. I want to see all possible Celestia eye candy. What kind of graphics card should I get?
5. How will Celestia perform on my system?
6. Why does the illumination level in Celestia not fall off the farther from the Sun I go - surely it should be very dark by the time I get to Pluto?
7. Celestia's galaxies are ugly, dim, grey blobs. How can I get colorful galaxies that look like the real things?
8. Positions on Mars are on the opposite side of the planet or bumps seem to be half a world away from the mountains or it's dark where it should be daylight. Why?
9. Why are some texture maps upside down and backward?
10. My planet's rings are drawn as a featureless oval. It used to work. What's wrong?
11. Problem on Ubuntu: Why does Celestia not have textures?
12. Older issues that should be solved

Installation of new graphic card drivers on Windows

1. General Information
2. Uninstalling the NVIDIA Display Driver Software
3. Installing the NVIDIA ForceWare Graphics Drivers
4. Graphics driver update procedure for Laptops

Crashes

1. Celestia crashes my computer.
2. Celestia crashes, what it draws is messed up or it's extremely slow. What can I do?
3. Celestia still crashes, draws funny stuff or is extremely slow. What can I do?
4. Why does Celestia always use 100% of the CPU?
5. How can I make Celestia use less CPU time?

Features

1. Why are my favorite stars not in Celestia?
2. Stars with HIP or HD designations sometimes show up in the "tab completion" line and sometimes do not. What's going on?
3. Why are there no stars in other galaxies than the Milky Way?
4. I want to write some scripts for Celestia. How can I do it?
5. How can I make Celestia work like a planetarium?
6. Why can't I see Mir or Galileo? I know they're defined in Celestia.
7. Celestia's orbit for the ISS is out of date. How can I get a better one?
8. I've placed a planet in orbit around a star in a binary system, but I only see light it lit by one of the stars. What's wrong?
9. How many simultaneous light sources can Celestia handle?
10. Ring and eclipse shadows don't look right when there are multiple light sources.
11. The Sun and the Moon are much too small in Celestia. What's wrong?

General Questions

1. Where can I get more information and documentation about Celestia?
2. Where can I get the most recent version of Celestia?
3. What changes have been made to Celestia since the last version?
4. I have a previous version of Celestia with tons of addons, custom textures, etc. How can I update to the latest version without having to reinstall all of those addons, textures, etc?
5. Why don't Windows and Mac addons work under Linux?
6. I have created pictures/videos with Celestia. May I sell them or use them for or in commercial productions?

Vista questions

1. General information
2. When trying to install the program on Vista the installer says it needs administrator rights which I don't have.
3. Why can't I make changes to files in the Celestia data directory?
4. What are compatibility directories?
5. I can't find/see those compatibility directories. Why?
6. Where are the files that I just edited and saved?
7. How do I use the 3dstocmod converter?
8. What causes Celestia to crash on Vista?
9. Addressing limitations
10. Do Cel:// URLs work under Vista?
11. What are the security impacts from Vista on Celestia?

Best regards,

Guckytos

[Guckytos]

Graphics

1. The Earth and other planets look strange. They have weird colors or do not look like globes. How can I fix this?
Answer:
Your graphics drivers might be incompatible with Celestia. Try the following, in this order:

1. Update the graphics drivers to the most recent version. See section »Installation of new graphic card drivers on Windows«.
2. Switch to "Basic" or "MultiTexture" render paths: type [Ctrl+V] several times.
3. Disable Celestia's vertex shaders: edit celestia.cfg (with a plain text editor) to remove the # at the start of this line
   

   Code: Select all

   # IgnoreGLExtensions [ "GL_ARB_vertex_program" ]
4. Disable 3D hardware graphics acceleration. You find that under Windows in the display properties.
5. If none of these work for you, please ask for help in the Celestia Help Forum.

2. Celestia is drawing planets and moons bright red. Why?
Answer:
Your computer's graphics drivers are obsolete. Celestia makes use of the most advanced features of OpenGL that the graphics driver claims to support. Modern drivers require that the program (Celestia) specifies the version of vertex shader routines that it uses. Obsolete drivers don't recognize that specification. When vertex shaders generate an error message, Celestia draws the object bright red.
Solution:
Download and install current drivers for free from the Web site of the manufacturer of your graphics hardware.
If you are using Windows make sure that you have disabled the feature to download graphics drivers from Microsoft. Those drivers have an outdated version of OpenGL included. Always use graphic card drivers from either the graphics card manufacturer or better directly from graphics chip manufacturer (i.e. NVIDIA, ATI/AMD, Intel, ...).
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.
For correct installation of drivers see point »Installation of new graphic card drivers on Windows«.
a) For PCs running Windows with plugin graphics cards, you can download the drivers for free from the Web site of the manufacturer of your graphics card. Make sure full hardware acceleration is enabled in your display properties.
b) For laptops and desktops running Windows with embedded graphics chipsets, you usually must download the most recent drivers from the Web site of the manufacturer of your computer. Sometimes generic drivers are available from the manufacturer of the graphics chipset.
c) 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.
d) 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.

3. The Moon is purple, blue and red. Why?
Answer:
Your graphics chipset and its OpenGL 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.)
Solution:
Install an updated graphics driver or try the workarounds described below.
Workaround 1: Turn off Celestia's advanced display features.
Type [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:
Workaround 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

Code: Select all

# IgnoreGLExtensions [ "GL_ARB_vertex_program" ]

(This avoids system lockups experienced under MacOS X 10.3.5 with ATI cards, and purple moons with Intel chips, for example. Intel chips don't have support for some of the graphics routines used by Celestia.)
Celestia's Help menu "OpenGL Info..." lists all of the routines in your OpenGL library. You might consider adding equivalent IgnoreGLExtensions lines for other suspicious routines.

4. I want to see all possible Celestia eye candy. What kind of graphics card should I get?
Answer:
The short answer is the following:
Any graphics card with at least 128MB of memory and support for OpenGL 2.0 pixel shaders will be able to show everything that Celestia is visually capable of.
Look for a graphics card that advertises either support for Direct3D shader model 2.0 or higher. Almost all graphics cards being sold today meet this requirement, albeit with varying degrees of performance. High-end NVIDIA and ATI cards will provide the best experience in Celestia. NVIDIA's OpenGL drivers have tended to have fewer bugs than ATI's.
Here are some recommendations for cards:
ATI Radeon HD series
GeForce 8xxx, 9xxx, and GTX 200 series

5. How will Celestia perform on my system?
Answer:
a) Only NVIDIA 5000 series or greater (e.g. 6000, 7000, 8000, 9000, 250) cards with 128MB of memory or more will show all of the eye candy drawn by Celestia v1.4.0 or later.
ATI Radeon 9500 and above, including the X series, are comparable to NVIDIA FX 5nnn series cards in functionality, although performance differs. However, not all of the eye candy drawn by Celestia is compatible with them.
b) Graphics cards with drivers that support OpenGL v2.0 will show all. Graphics cards that support only v1.4 will show most, but not all, eye candy.
E.g. NVIDIA GF4 Ti 4xxx series cards cannot show smooth shadow borders. Starting with Celestia v1.4.0, smooth shadow borders can be drawn by any card which supports OpenGL v2.0.
c) Other cards work, but with various additional limitations.
Some specific limitations:

• NVIDIA MX cards cannot shadows of rings on planets, although they can draw shadows of planets on rings.
• ATI Rage cards cannot show specular highlights or bumpmap shadows.
• Textures on Rings, 3D Mesh models, and moving Clouds are limited to the size of your card's texture buffer. This limitation does not apply to the surface textures of spherical planets and moons.

Therefore...
Most ATI cards, including the X series, cannot show surface texture images larger than 2K (2048 pixels on the longer side) on a side on Rings, on 3D Mesh models, or on moving Clouds. Unfortunately, some addons include 4K (4048) pixel textures. Those addons only work with NVIDIA 4nnn, 5nnn, 6nnn and 7nnn cards and with ATI X1800 and above with ATI's most recent graphics drivers. Those cards have 4K texture buffers.
In order for Celestia to be able to show bumpmap shadows and specular reflections, your card's OpenGL library must support OpenGL v1.4. In particular, it needs to include "GL_ARB_vertex_program".

6. Why does the illumination level in Celestia not fall off the farther from the Sun I go – surely it should be very dark by the time I get to Pluto?
Answer:
The human eye can adapt to a very wide range of illuminations, so it wouldn't be as dark out there as you think – about the level of moderate indoor lighting, in which you can see very well. At the other end of the scale, your computer monitor is physically incapable of generating the brightness of illumination that pertains on the inner planets. Fortunately it doesn't need to, since all that would happen would be that your pupils would constrict to reduce the incoming light to a more comfortable level.
So in summary:
a) There's no way Celestia can display "realistic" brightness on your computer screen,
b) such "realism" is unnecessary because your eyes merely adapt to compensate.

7. Celestia's galaxies are ugly, dim, grey blobs. How can I get colorful galaxies that look like the real things?
Answer:
The real things are dim, grey blobs. Your eyes are not sensitive to color at the very low light levels emitted by distant galaxies.
Many of the colorful pictures you're used to seeing are enhanced by long exposures on sensitive color film. Others are imaginative "false color" combinations of narrow-band CCD images designed to make visible the specific features of interest to the investigator. The colors of those pictures aren't realistic at all.
Solution:
You can add a colorful object to Celestia by creating a 3DS model with appropriate images as surface textures. Define it as a Nebula in a DSC file. Use the Search command in the Celestia "Development" and "Add-On" forums to find examples.
Galaxy brightness can be increased by typing a [)] (Shift+0) or decreased by typing a [(] (Shift+9) (on english keyboard layout).

8. Positions on Mars are on the opposite side of the planet or bumps seem to be half a world away from the mountains or it's dark where it should be daylight. Why?
Answer:
You have a misaligned map.
Celestia requires that all maps have 0 degrees of longitude in the center, with 180 degrees of longitude at the edges. All of the surface texture image maps of all of the moons and planets that come with Celestia have this alignment.
In contrast, many maps of Mars were created with 0 degrees of longitude at the left and right edges, and with 180 degrees of longitude in the center.
Using a map with 0 at the edge would cause the symptoms you describe.
Solution:
You need to find a map that's properly aligned or you need to cut the map in half and exchange the halves.
For example with Photoshop's 'Offset' filter is quite easy to modify maps that are misaligned by 180 degrees. In Photoshop CS2, select Filter/Other/Offset and set the horizontal offset amount to half the texture width.

9. Why are some texture maps upside down and backward?
I compared the Celestia textures for Venus, Ida and Miranda with some I found in a book or on the Web, and Celestia's maps are upside down.
Answer:
Many sources for planetary maps (such as the USGS) use a mapping convention called "ecliptic north" – the north pole of any planet or asteroid is defined as being whichever rotational pole points north of the plane of the ecliptic (the plane of the Earth's orbit around the Sun). Each planet or asteroid can then be classified as a "direct" rotator, if it rotates in the same direction as the Earth when observed from above its north pole (i.e. counterclockwise); or as a "retrograde" rotator, if it rotates in the opposite direction.
In contrast, Celestia uses an equally valid mapping convention called "rotational north" – north is defined as being the pole around which the planet appears to rotate counterclockwise, irrespective of that pole's orientation relative to the ecliptic.
For direct rotators, this difference is irrelevant – "north" turns out to be the same direction in both mapping conventions. But for retrograde rotators, Celestia's north pole corresponds to ecliptic south – so you will find many maps of retrograde rotators like Venus, Ida and the moons of Uranus that appear to be upside down relative to those in Celestia.
Solution:
If you want to convert such maps for use in Celestia, you'll have to turn them through 180 degrees.

10. My planet's rings are drawn as a featureless oval. It used to work. What's wrong?
Answer:
You need to use a smaller ring image, one that is no wider than the maximum texture size supported by your graphics card. To find out how big this size is, use the "OpenGL Info..." option in Celestia's help menu. Near the beginning it has a line that starts with "Max texture size:".
For most graphics cards, the texture size limit is at least 2048.
Solution:
You need to use a smaller ring image, one that is no wider than the maximum texture size supported by your graphics card.

11. Problem on Ubuntu: Why does Celestia not have textures?
Answer:
The version of Celestia supplied in the package manager or the Add/Remove programs menu is broken. Celestia's textures are included in the package celestia-common-nonfree which is not listed as a dependency of the main program, so is not installed by default.
Solution:
To fix this issue, either install the celestia-common-nonfree package through the package manager, or type in a terminal window

Code: Select all

sudo apt-get install celestia-common-nonfree

12. Older issues that should be solved.
These issues shouldn't normally happen with the recent Celestia version. But just in case IF they happen anyway, here are the solutions.
Sometimes when Celestia captures an image of its window, there's an ugly bright rectangle in the picture. How can I get rid of it?
Answer:
Sometimes a bright area is recorded where the file requestor menu or any other window overlaps Celestia's main window.
This bug seems to be fixed since Celestia v1.4.0, but if it happens here are some tips for avoiding this problem.
Solution:
a) The problem will often go away if you toggle "Show Galaxies" off and on again before you take your snapshot.
Either use the Render/View Options menu or type the letter [U] twice before you press [F10].
b) Run Celestia in windowed mode, not full-screen. Drag the file requestor away from in front of the main window before you click on "Save".
c) If your graphics card supports it, you can connect a secondary display. Some CRTs are very inexpensive. Drag the file requestor to the other screen.
d) Use an external screen-dump command or program.
Windows includes a "print-screen" command. Under XP, you can use the keyboard combination [Ctrl+Print-Screen] to write the screen image to the clipboard. You can then use any Paint program and Paste the image into it.

Sometimes a screenshot captured in Celestia will have multiple boxes around it, as if Multiview was on. How can I get rid of it?
Answer:
This is a bug in Celestia.
Solution:
To make a good clean screenshot image, press [Ctrl+D] before you capture the image. This cancels Multiview.

When I try to capture a picture or movie, the image is stretched out of proportion.
Answer:
This sounds like a bug with anti-aliasing with older cards/drivers. Here are three things you can try...

1. Check the OpenGL anti-aliasing setting of your graphics card. If it is on, try turning it off, or setting it to another option. This seems unrelated to the anti-aliasing setting inside of Celestia.
2. Set your graphics card OpenGL options to "default".
3. Get the most recent drivers for your graphics card.

[Guckytos]

Installation of new graphic card drivers on Windows

1. General Information
Be sure to use the following general procedure when installing new graphics drivers:

1. Download driver installation program from graphic chip manufacturer website (i.e. NVIDIA or ATI/AMD)
2. Use the Control Panel / Add or Remove Programs menu to delete the current graphics drivers.
3. Reboot your PC
4. Cancel out of Windows' 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.
Next section shows in detail how to do it for an NVIDIA card. The procedure is the same for cards by other vendors.

2. Uninstalling the NVIDIA Display Driver Software
Note: It is highly recommended that you follow the steps in this section to completely uninstall
the NVIDIA Display Driver software before updating to a new version of the software.
To uninstall the nView software, follow these steps:

1. From the Windows taskbar, click Start > Settings > Control Panel to open the Control Panel window.
2. Double-click the Add/Remove Programs item.
3. Click the NVIDIA Display Driver item from the list.
4. Click Change/Remove.
5. Click Yes to continue.
   A prompt appears asking whether you want to delete all of the saved nView profiles.
   
   • If you click Yes, all of the nView software and all of your saved profiles will be deleted.
   • If you click No, the nView software is removed, but the profile files are saved in the Windows\nView directory on your hard disk.
6. Your system now restarts.

3. Installing the NVIDIA ForceWare Graphics Drivers

1. Follow the instructions on the NVIDIA website driver download page to locate the appropriate driver to download, based on your hardware and operating system. (You can already do this step, before you uninstall the old drivers.)
2. Click the driver download link.
3. The license agreement dialog box appears.
4. Click Accept if you accept the terms of the agreement, then either open the file or save the file to your PC and open it later.
5. Extract the zip files to a temporary folder on your PC.
6. Open the NVIDIA driver installation .EXE file to launch the NVIDIA InstallShield Wizard.
7. Follow the instructions in the NVIDIA InstallShield Wizard to complete the installation.
8. Reboot your system, if it hasn't already been rebooted by the installation program.

4. Graphics driver update procedure for Laptops
Note: Older Laptops/Notebooks will need a driver from the web site of the manufacturer of the laptop (not from NVIDIA)!
Depending on the brand of laptops and the used card, it may take special action to update graphics drivers by the standard ones from the NVIDIA site. Normally, for these laptops, one has to update the drivers from the vendor's site instead. The reason is that in such cases, the laptop requires a modified .inf file together with the standard driver. This typically happens in case of NVIDIA GO graphics cards!
For example only most recent DELL machines work with the standard drivers from the NVIDIA site. These cases are listed explicitly by NVIDIA ...
A typical signature for the situation is a message like the following during the installation of the standard NVIDIA driver:
"NVIDIA setup program could not locate any drivers that are compatible with your current hardware. Setup will now exit."
Solution:
a) Download the drivers from your laptop manufacturer.
b) Try what is described below if a) doesn't work (you are at your own risk).
Note: If you are using what the below mentioned sites are offering we take no responsibility if anything goes wrong, you should know what you are doing and carefully read all instructions first before using the instructions given there.

There is a site where the appropriately modified .inf files are offered, such that the standard NVIDIA driver update may be loaded without complaints by the particular laptop.
http://www.laptopvideo2go.com/

Besides offering Basic info http://www.laptopvideo2go.com/forum/ind ... topic=9243
and a FAQ http://www.laptopvideo2go.com/forum/ind ... opic=10561
this site also offers step-by-step instructions for VISTA http://www.laptopvideo2go.com/forum/ind ... opic=11997

[Guckytos]

Crashes

1. Celestia crashes my computer.
Problem:
I can install it, no problem, but it won't even start up, it loads, then freezes. Then it crashes my computer, forcing it to restart.
Answer:
These kind of problems usually are caused by buggy graphics drivers. Please install the most recent drivers available for your graphics card and try again. Windows users see point »Installation of new graphic card drivers on Windows«.

2. Celestia crashes, what it draws is messed up or it's extremely slow. What can I do?
Answer:
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.
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:

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, since those have only older implementations of OpenGL incorporated.

3. Celestia still crashes, draws funny stuff or is extremely slow. What can I do?
Answer:
Report the exact circumstances and details of your system, graphics 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: 2 GB 1.95 GHz Core2Duo, Windows XP SP3
Graphics: 256MB NVIDIA GeForce 7950 GT, ForceWare 169.21, OpenGL 2.1.2
Program: Celestia v1.6.0
If you're running Windows, details are usually available in the Control Panel's System Properties menu.
Some of the graphics information can be found in Celestia's Help menu under "OpenGL Info..." Under Windows more details can be found in the Control Panel's Display Properties menu.
You can also report bugs on the SourceForge bug tracker; but before you do so, please check in the Celestia Bugs forum if it has already been reported or solved.

4. Why does Celestia always use 100% of the CPU?
Answer:
Celestia uses 100% of the CPU if it cannot finish recalculating what's shown in its window before your computer decides it's time to refresh the screen.
Celestia has to recalculate the positions and visibility of everything you see in its window every time your system refreshes its screen. If you have set the screen refresh rate to be 75Hz, then Celestia has to recalculate everything in 1/75 of a second. If it finishes recalculating everything before the screen is refreshed, then it will use less than 100% of the CPU. If it takes longer, then it will use 100% of the CPU and Celestia will redraw its window more slowly than the screen's refresh rate.
In a dual processor or dual-core system or in a hyperthreaded system simulating a dual processor system, 100% of one of the CPUs is shown as 50% of total system usage. The calculations in Celestia are single-threaded and cannot make use of more than one CPU at a time.
Type a [`] (= backslanted apostrophe = accent grave) to enable Celestia's fps (frames per second) display in the lower left corner. If you have a keyboard that supports diacritical marks, then you may need to type a [SPACE] after the [`].

5. How can I make Celestia use less CPU time?
Answer:
On most systems Celestia will use no CPU time if its window has been iconized or minimized. (Under Windows, click on the icon in the upper right corner of Celestia's window which has an underscore in it.)
Also check if vsync is enabled in the Windows control panel (this is the default setting.) If vsync is not enabled, Celestia will render frames as fast as it can, even if this is faster than the rate at which the monitor can display them.
You also can make Celestia use less of the CPU if you ask it to draw less. Some ways to do this are

• reduce the screen refresh rate
• reduce the size of the window
• reduce the size of objects drawn in the window so fewer stars and galaxies are obscured
• reduce the number of stars and galaxies being obscured by turning down the limiting magnitude (type a [ several times) or by disabling them entirely
• reduce the number of objects being drawn by loading fewer addons.

Otherwise, consider upgrading your CPU so more can be calculated between screen refreshes. Upgrading the graphics card will help somewhat, depending on how many OpenGL functions get moved from software into hardware.

[Guckytos]

Features

1. Why are my favorite stars not in Celestia?
Answer:
Celestia's primary star catalog is based on the Hipparcos database of stars with accurately measured distances. Hipparcos was not used to measure the distances to many dim, variable or close double stars.
More recent versions of Celestia include all of the stars within 20 LY of the Sun, as well as about 200 double stars. (There are actually many more double stars than that, but relatively few have had their orbital parameters accurately measured.)
Another possibility is that Celestia does not know this name of the star that you are looking for. A lot of stars have more than only one name/designation, some even more than 30. If you can't find the name that you are looking for, try an online resource like SIMBAD to find other names for the star.
Solution:
Someone may have created an Add-on that includes your stars, though. So you could try to look for it in the Add-on repository. Or consider creating the necessary STC file yourself and contributing it.

2. Stars with HIP or HD designations sometimes show up in the "tab completion" line and sometimes do not. What's going on?
Answer:
Only quoted Star "names" are shown in the tab completion line. Stars that have only a HIP catalog number are not listed in the tab completion line. When you want to select a Star that has only a HIP or HD catalog number, you must type its complete designation, including a space between HIP (or HD) and its number:

[return]
HIP <space> 111111
[return]

Strings which only match entries in the binary stars.dat database or in one of the cross-index databases for HD and SAO designations are not shown by the tab-completion code. There are too many of them. Only names which are in an object's quoted textual name string in a textual catalog (SSC, STC or DSC) are listed by the tab-completion code.
A confusion factor is that some Stars have HIP designations specified as their quoted names, often with no space between HIP and the number. Only these quoted HIP names are shown in the tab completion line. Some examples are in /data/visualbins.stc

3. Why are there no stars in other galaxies than the Milky Way?
Answer:
Up to version 1.5.1 Celestia had technical limitations which prevented it from drawing stars beyond a distance of about 16,000 LY from the sun.
Since version 1.6.0 Celestia is technically capable of displaying stars without a distance limitation. However, since Celestia is scientifically orientated only stars that have a precise measurement of their position are included in the star database of the official releases.
With increasing distances of the stars from the Earth the measuring error of a star position gets huge, so it is not possible to exactly say where the star should be. Those stars are not included in Celestia and this criterion is also the reason why there are no stars displayed in other galaxies.

4. I want to write some scripts for Celestia. How can I do it?
Answer:
A)
Celestia includes a very simple scripting language of its own which understands commands like "go here, look there, set flag, display text". These commands should go into a file with the filetype .CEL

• An example .CEL script is Celestia's own start.cel, which is on your computer in Celestia's main directory.
• A .CEL Scripting Guide is available in English and German on the Documentation Page of the Celestia MotherLode.
• Selden's Celestia Resources website includes a list of some of the more recently added .CEL scripting commands, but they're rather cryptically organized.
• Information can also be found in the Scripting section of the Celestia Wikibook.

B)
The Lua programming language is available for use in .CELX scripts. See http://www.lua.org/.

• A few example Lua scripts for Celestia are available on SourceForge at http://celestia.cvs.sourceforge.net/celestia/celestia/scripts/
• A .CELX Scripting Guide is available in English on the Documentation Page of the Celestia MotherLode.
• More information about CELX is available on Harald Schmidt's web site at http://celestia.h-schmidt.net/

C)
You can use any language you want if it can pass commands to the operating system's command interpreter: It can run Celestia and tell it to run a .CEL Celestia script or .CELX Lua script.
When invoked from a command line, Celestia can be passed the name of a .CEL or .CELX script to run at startup:

Code: Select all

./celestia --url name-of-script.cel

When the command line includes the qualifier "--once", the command line will be passed to the running copy of Celestia instead of starting a new copy of the program. (note: two hyphens)

Code: Select all

./celestia --once --url name-of-script.celx

Note: Scripts may be in any folder. But it helps with your organization of your Celestia folders if you keep them in a folder named /scripts/.
For more information, please visit and contribute to the Celestia Scripting Forum.

5. How can I make Celestia work like a planetarium?
I want to see how the sky should look from my backyard.
Answer:

• Select the body from which to observe; the Earth for example.
• Use the GoTo menu to specify your Longitude and Latitude and GoTo there (lat & long are entered in decimal format – there are websites that convert to/from degrees/minute/seconds format.)
• Type a [Y] = Sync Orbit (this locks you into position above the location you set)
• Under Windows, Linux-GTK and Linux-Gnome:
  
  • Type a [Ctrl+G] = GotoSurface
  • Type a [Ctrl+F] = change Arrow keys to AltAzimuth mode (This keeps the horizon level when panning left & right.)
  • Use the arrow keys to look toward the sky, you can adjust the field of view (FOV – how much sky you see at once) with the [,] & [.] keys.
• Under Linux-KDE3:
  
  • Type an [Alt+S] = GotoSurface
  • Type an [Alt+F] = change Arrow keys to AltAzimuth mode (This keeps the horizon level when panning left & right.)
  • Use the arrow keys to look toward the sky, you can adjust the field of view (FOV – how much sky you see at once) with the [,] & [.] keys.
• Activate the alt-azimuth coordinate display by selecting the "Horizontal grid" in the "View options" dialog.

6. Why can't I see Mir or Galileo? I know they're defined in Celestia.
Answer:
Mir along with other spacecraft models were modeled within an historical time frame and can only be viewed from their starting date to their ending date.
Celestia will show those spacecraft only if you set the time to be somewhere between those two dates. Celestia does not display spacecraft if they are not in orbit at the time of the simulation.
For example, Mir was launched on February 20, 1986, and reentered the Earth's atmosphere on March 23, 2001, at 05:55 GMT.
This is controlled by Beginning and Ending directives in the definition of Mir in solarsys.ssc. If you remove those statements, Celestia will always draw Mir in orbit.
You can override ending dates by opening the solarsys.SSC or other specific craft related .SSC files and placing a pound sign (#) in front of the ending date string. Then save the new setting. This way you can always view your installed Space Crafts. Consequently, removing the pound sign will return the craft to it's natural time frame.

7. Celestia's orbit for the ISS is out of date. How can I get a better one?
Answer:
The orbit of the ISS changes continuously in ways that are almost impossible to predict due to things like atmospheric drag, light pressure, cargo ship docking, etc. If you want an accurate orbit, you'll have to update it on a daily basis.
ISS TLEs (Two Line Elements) are posted to the AMSAT SAREX mailing list regularly by "Dave Larsen PhD". See here.
Here are the ISS TLE orbital parameters for August 16th, 2004:

ISS
1 25544U 98067A 04229.23839543 .00019757 00000-0 15906-3 0 4532
2 25544 51.6323 19.1941 0005251 117.9988 304.8582 15.70921896327755

Grant Hutchison has provided a spreadsheet to convert TLEs into Celestia SSCs here.
Also, don't forget that Celestia models the shape of the Earth using a spheroid. The actual shape of our planet is much more complicated. As a result, a view from the Earth's surface in Celestia is not accurate enough to show the correct path across the sky of satellites in low Earth orbit like the ISS. In other words, you can't use Celestia to find out where to look in the sky to see the ISS.

8. I've placed a planet in orbit around a star in a binary system, but I only see light it lit by one of the stars. What's wrong?
Answer:
It's likely that this is correct behavior. The distance between the planet and the star it orbits is probably much less than the distance from the planet to the second star. If the stars are approximately equal absolute brightness, this means that the light from the closer star will be so much more intense than the light from the more distant star that the secondary illumination will be imperceptible.
Remember that the brightness of light falls off in proportion to one divided by distance squared. If the second light source is a lot further away than the primary, it must be intrinsically much brighter in order to visibly illuminate a planet.

9. How many simultaneous light sources can Celestia handle?
Answer:
Up to two in the OpenGL vertex shader paths, and up four in the basic, multitexture, and OpenGL 2.0 paths. The light sources with the greatest apparent brightness are given priority.

10. Ring and eclipse shadows don't look right when there are multiple light sources.
Answer:
Only the OpenGL 2.0 render path handles shadows correctly when there is more than one light source. In the other render paths, only the shadow from the brightest light source is considered. The OpenGL 2.0 path can render ring shadows and up to three eclipse shadows per light source.

11. The Sun and the Moon are much too small in Celestia. What's wrong?
Answer:
Their diameters are exactly right. As seen from the earth, they are both about a half-degree across. Celestia's window is about 45 degrees across, so the Sun and Moon are about 1% of that. They are drawn only 10 pixels wide if your screen is 1024x768.
Remember that your computer screen is only about 10-20 degrees wide in your own field of view. Celestia's 45 degree field provides a "wide angle" view of the sky. This makes objects look smaller than you might expect.
The apparent large size of the Sun and Moon as we see them in the sky is a psychological illusion. There are several different explanations for this. If you take a picture of the moon with a camera lens that has the same field of view as Celestia, you may be surprised at the small size of its image.
At least one book has been written about this effect:
The Mystery of the Moon Illusion: Exploring Size Perception
By Helen Ross and Cornelis Plug

[Guckytos]

General questions

1. Where can I get more information and documentation about Celestia?
Answer:
A good start is the documentation on the Celestia Website and the pages on the Celestia Motherlode documentation. For example an introductory User's Guide by Frank Gregorio is available in English. Translations into German, French and a few other languages also are available. Consider providing a translation into another language yourself.
An other good place to look for or ask for additional information is the Celestia Forum. You'll find lots of friendly people there.
Selden Ball's website has pointers to additional documentation on catalog files (SSC, STC, DSC), planet surface textures, etc.
Also you can find information in the Celestia WikiBook.
On the Celestia Motherlode there are also many other Celestia resources and addons for download.

2. Where can I get the most recent version of Celestia?
Answer:
Get the most recent Celestia installation file from SourceForge. They have many mirrors for best performance.
Official prerelease versions are announced in the Celestia Web Forum in its Users Forum.

3. What changes have been made to Celestia since the last version?
Answer:
The developers maintain a list of all new functionality and bug fixes in the Celestia ChangeLog, which is located at SourceForge. Look at the top-most entry in the list, to the right of where it says "Revision #.##", click the "(view)" link to display the most recent ChangeLog.

4. I have a previous version of Celestia with tons of addons, custom textures, etc. How can I update to the latest version without having to reinstall all of those addons, textures, etc?
Answer:
You can have more than one copy of Celestia on your system at the same time.

• Rename the directory (folder) where you have Celestia now, maybe to Celestia151.
• Verify that things still work:
  
  • Double-click on the icon for Celestia151\Celestia.exe and look around in your universe.
• Install the new copy of Celestia and tell it to use the directory Celestia. It'll create the folder again and install itself there.
• Move your addons at leisure.

Cel:// URLs run the copy of Celestia that is in the folder named Celestia. If you want to change back to using your old Celestia that way, just rename the directories again: rename Celestia to be Celestia160 and rename Celestia151 to be Celestia.
Also, please take a look at http://www.lepp.cornell.edu/~seb/addon-intro.html for a description of how to organize your addons so they can be moved easily.

5. Why don't Windows and Mac addons work under Linux?
Answer:
Always use only lower case letters and numbers in file names. Use only the underscore [_] as word separators, not spaces. Avoid using composite characters.
Too often people are careless with filenames when creating addons. The capitalization of names must be consistant for an addon to work under all operating systems.
My_Addon.dsc is not the same as my_addon.DSC and not the same as my_addon.dsc. They are names for different files.
Linux and other Unix derived operating systems can tell the difference between upper and lower case. Linux can have three different and separate files with those names.
If you specify:
Texture "texture.jpg"
in the catalog file, then the filename must be texture.jpg in the textures folders. If the file is named Texture.JPG, Celestia won't find it because that's not the file that it's looking for.

6. I have created pictures/videos with Celestia. May I sell them or use them for or in commercial productions?
Answer:
The answer to that question is twofold.

1. If the pictures and movies were created by you by using only the official distributed copy of Celestia they are yours to do with as you want. In any case if you are using pictures/videos made with Celestia you have to recite Celestia as the origin.
2. If you create pictures or movies using Addons, however, then you have to abide by the license of that Addon. Most Addon creators allow their works to be used freely for educational purposes, but forbid commercial use. In any case it is a good idea to contact the creator of the Addon and ask for his permission.

[Guckytos]

Vista questions

1. General information
A lot, if not all problems described are due to the fact that windows doesn't allow data to be placed in the program files directory.
That is part of the security system (UAC) and can be turned off completely, or partly.
To enhance compatibility and still use UAC Microsoft implemented a work-around for programs, by redirecting data into the "compatibility" directory.
Another way would be to install the complete Celestia program, including its sub-directories anywhere, away from the "Program Files" directory. Some people have reported having fewer problems if they install Celestia somewhere else than in "Program Files".

2. When trying to install the program on Vista the installer says it needs administrator rights which I don't have.
In earlier versions there was no need for administrator rights. Why does this version require administrator rights, and is this something that can be fixed?
Answer:
The administrator rights are caused by the installation itself. Celestia wants to retain its own authorities when you install it, and that creates these problems.
The only way to fix it is to either reset the permissions which you cannot do unless you have the administrator rights, or you can copy the files to a location that you have created yourself.
Solution:
Set up a different folder for Celestia and simply copy all the original files to the new folder. That is if you can.

3. Why can't I make changes to files in the Celestia data directory?
Answer:
The short answer is – when installed with the default options – Celestia takes ownership of the directory, so you simply cannot make any changes to the files in the data directory.
Well, you can make the changes, it's just that you simply cannot save the changes to the data directory. This problem can be overcome by some work with permissions and security within Vista.
You cannot change the celestia.cfg file, by the way, if you've installed Celestia in "Program Files" or "Program Files (x86)".

Solution 1:
To avoid having to deal with all of these "permissions" issues, Vista users (on a single home PC) can simply copy a SSC file to a different directory.
Make any changes to the copied version, then copy it back to the C:\Program Files\Celestia\data folder.


You will be asked if it's okay to allow this copy, and you can respond Yes. Once you have done this you will be able to edit the copied file in the Celestia directory without trouble.

Solution 2:
Tell Celestia's installer to put Celestia in some directory other than "Program Files", into C:\Celestia perhaps. Only the "Program Files" directories have these restricted access issues.

4. What are compatibility directories?
Answer:
Generally, the compatibility directories are created when you try to install Celestia as an application defined as being associated with a previous version of Windows, i.e. XP, 98, etc.
Solution:
Most of the compatibility directories will not be created if you install Celestia as a native Windows Vista application.
Running Celestia in the native Vista mode seems to work pretty well. You may find also that you can simply move a compatibility file from its current location (once it has been created) into the standard Vista C:\Program Files\Celestia directory where you wish it to be. Once done, it will usually stay where you put it unless it is again acted upon by a non-Vista program.
If you also use other programs to perform functions like editing plain text SSC files using previous Windows version compatible programs, these will also cause compatibility directories. So, it is the best to use Vista-ready programs for all of the Celestia-related functions.

5. I can't find/see those compatibility directories. Why?
Answer:
These files are "hidden" in the normal Vista environment (and in Windows Explorer) if you use the default values of Windows.
If you want to see these files, or to see if there are any compatibility files in use, here is a short explanation of how to enable the view of "hidden" files in Vista's Explorer.
With standard installation of Windows your compatibility files should generally be found under the User's Folder. These compatibility files cannot be seen unless the user has the ability (using Windows Explorer) to show the hidden files.
This is done (in Windows Explorer) by clicking on the "Tools" option on the Explorer Menu, followed by "Folder Options", "View", then clicking on "Show hidden files and folders" and finally clicking on "Apply" in order to show these files and folders.
After this has been done, you can then look to the previously hidden folder named "AppData" to see if compatibility files are in use for Celestia.

6. Where are the files that I just edited and saved?
Answer:
On occasion Vista creates copies of your textures or other Celestia files when they were modified. Your new textures may not show up in the Celestia textures directory, but may be transported to an entirely different directory used for compatibility issues.
Some textures will show up in the compatibility directory, and others will show up where you saved them in the Celestia directory.
Your texture may be either in: C:\Program Files\Celestia\textures\medres
OR, it will be in: C:\Users\YourName\AppData\Local\VirtualStore\Program Files\Celestia\textures\medres
It is possible to go to the compatibility directory, and move or copy the compatibility file directly back to the Celestia directory.

7. How do I use the 3dstocmod converter?
Answer:
In order to use the 3dstocmod converter in Vista, you have to convert the elements via Vista's "compatibility" mode under the file's "properties" dialog.
For every .exe and .dll file, you must specify compatibility for Windows XP, and you must specify that "Visual Themes" are to be disabled.

8. What causes Celestia to crash on Vista?
Answer:
Celestia will crash if you do not have up-to-date graphics drivers. The graphics drivers included with Vista are buggy and not up-to-date. You must download and install updated drivers from the Web site of the manufacturer of your graphics hardware.
Do NOT use Microsoft offered graphics drivers, since they have not the support for the latest OpenGL features, even if your graphics card is capable of providing them.

9. Addressing limitations
Celestia is a 32 bit application, so it's limited to somewhat more than 2GB RAM. However, it works fine under both Vista 32 and Vista 64.

10. Do Cel:// URLs work under Vista?
Answer:
Cel:// URLs work fine under Vista with Word 2007.
MS Word automatically requires the use of [Ctrl] + click to launch a hyperlink, but there is a menu item to eliminate the need to press [Ctrl].

• Go to the Tools/Options/Edit menu, and uncheck the box that says, "Use Ctrl+Click for hyperlinks".
• Click OK.

From that point forward, simply pointing and clicking once on a cel:url or hyperlink will launch it.

11. What are the security impacts from Vista on Celestia?
Answer:
Vista enforces some security requirements which usually are optional under earlier versions of Windows. You may have to select options to disable that enforcement for Celestia. E.g. allowing URLs to run programs.