Most Addons consist of 1, 2 or 3 sets of files:
One or more Catalog files. These describe where the objects are in space.
1.2: Surface pictures (texture maps) for those objects. These give the objects a unique appearance.
1.3: Models of the objects. These give them special shapes.
File locations. Each type of file goes into a particular directory.
Although they're all plain text files, different keywords are used in the different types of Catalog files. You can't rename a .SSC file to be a .STC file, for example.
The first part of a Catalog file's name doesn't matter. Celestia tries to load all of the .SSC, STC and DSC files that it finds. The first part of the name is to help you keep track of which file is for what.
Celestia only reads in Catalog files when it starts up. If you modify an old file or add a new Catalog file, you have to exit from Celestia and start it up again so it can find the new file.
Unfortunately, some Addons don't include a Catalog file. Their authors leave it up to you to create one.
Celestia includes its own SSC file that defines all of the planets
and many of their moons, along with asteroids, comets and a few
spacecraft. This is the file named
directory. Some Addons provide better surface textures for objects in
our solar system.
If you're careful to make a copy, you can modify
solarsys.ssc to use one or more of these textures
instead of the ones provided with Celestia.
See also "Creating and using .SSC files".
Lots of people enjoy making replacement surface textures for existing planets or moons. For them, you either have to rename the image files to match the ones specified in the appropriate .SSC file, or you have to edit the .SSC file so it looks for the name of the new surface texture file.
Celestia comes with many surface textures already
although it doesn't come with any
hires images. It's best
not to mix your images among those that Celestia uses. Use a
separate subdirectory instead. See Section 1.4 below.
See also "Creating Textures for Celestia".
Objects with complicated structures can be created using a 3D design package. Celestia can understand models that are defined in the 3DS file format. This format was originally used by the 3D modelling software named "3D Studio Max". Most 3D design programs can create 3DS files if you use their "Export" command.
Models can be designed either to require particular surface texture
files or to accept a surface texture specified by Celestia. When
surface textures are specified in a model, Celestia loads them from
Celestia v1.3.0 (and later) lets you organize your Addon files. Previous versions
of Celestia required that the files be mixed in with the ones that come
As a result, many older Addons put their files into the
directories that Celestia uses itself:
This causes lots of confusion when you install a
new version of Celestia.
Starting with Celestia v1.3.0, Addon files can go into a separate
Celestia subdirectory (folder) that you
create within Celestia's
Now when you install a new version of Celestia, you can simply drag
that whole Addon directory into the
extras directory of the new version of Celestia.
You no longer have to keep track of which files you added, which ones belong
to which Addon, and which came with Celestia.
Here's one way to organize Addons:
extrasdirectory which has the name
addons. This will let you move all of your Addons at once by moving just this one directory.
addonsdirectory, create a directory for each Addon when you install it. For example, you might create the
NGC2237directory, you must create the directories for its models and its surface textures: create the directories
textures. Within the
texturesdirectory, create the directories
When you've finished, your directory structure might look something like this:
An older Addon, one which was created before this new directory
layout became possible, usually includes an
directory containing all of its catalog files.
Those files all must be moved into
the Addon's main directory and the
\extras\ that was provided with the Addon
should be deleted.
medresdirectory. For example,
NGC2237.pngshould go into the directory
hiresthat are in a Celestia subdirectory named
If there is only the one texture file with a unique name, Celestia will look in all three directories while trying to find it.
If there are texture files with the same name in more than one of the
subdirectories, you can toggle among them using the "r" and "R"
models. For example,
NGC2237.3dsgoes into the directory
When a 3DS model specifies texture maps in the model itself, those
texture files must go into the
medres directory. Celestia
does not yet provide a way to select different resolution surface
textures in this case.
If you don't tell me that something's missing, unclear or wrong, I can't improve it.