A (not so) Brief Introduction to Celestia Addons Part 3 (3rd edition)
Contents
3: Installing a Simple Nebula Addon.
Here is an example for installing a relatively simple Nebula Addon.
I'll assume you're using some version of Windows, although equivalent
operations should work with the MacOS X and Linux versions of Celestia.
If you've ever downloaded and installed other software, I'm sure
this description will be full of things you already know how to do.
You should be able to use similar procedures for other Addons.
Essentially, the steps are:
3.1: Download the Zip archive file containing the Addon you want
3.2: Create the directory tree to contain the Addon.
3.3: Copy the Addon files from the zip archive to the
appropriate Celestia directories
3.4: Start Celestia and view the object.
In detail:
3.1: Download NGC3372
If you haven't already, download the zip archive containing a
simple Eta Carinae Nebula Addon. This nebula is also known as NGC 3372.
3.2: Create the directory tree for NGC3372, if necessary
If you use an unZip program to restore the entire archive,
it should automatically create the necessary directories.
Alternatively, if you have a "visual" unZip program,
you can drag the NGC3372 folder out of the Zip archive into your Addons
folder. That single operation will recreate all of the folders and files
in the right places.
If you want,
however, you can create all of its directories by hand and then drag
the files individually from the archive into them.
Here are the details of this manual procedure:
- If you haven't already done so, create a directory (folder)
within Celestia's
extras directory
which has the name addons.
This will let you move all of your Addons at once by moving just
this one directory.
- Within the
addons directory, create a directory for
each Addon when you install it. For example, you might create the
NGC3372 directory.
- Within the
NGC3372 directory, you must create the directories for
its models and its surface textures: create the directories
models and textures Within the
textures
directory, create the directory
medres.
(The lores and hires directories aren't needed
for this particular Addon.)
When you've created the new directories,
your directory structure might look something
like this:
3.3: Copy Addon files
Here's the "difficult" drag-and-drop method of installing the
Addon. You also can have Zip extract and install the files directly
into the appropriate subdirectories, but the steps below will help you
understand what's supposed to happen.
You need to have a ZIP program installed to extract the files.
(Windows XP comes with one built in.)
- Double click on the Zip archive file NGC3372.ZIP.
A new unZip window should open showing the files that are in the
archive.
This Addon has 4 components:
- A Deep Space Catalog describing the Nebula NGC 3372,
ngc3372.dsc,
- A STar Catalog describing Eta Carinae,
eta-car.stc,
- A 3DS model to hold the picture of NGC 3372,
ngc3372.3ds, and
- A JPEG picture of the nebula,
ngc3372.jpg.
All of the Catalog files for an Addon,
whether they're .STC, .DSC or .SSC,
go into the same "root" directory.
3.3.1: The Deep Space Catalog
######################
# NGC 3372
#
# The accompanying image of NGC3372 was derived from 02192.TIFF
# at http://www.noao.edu/image_gallery/html/im0061.html
# Original tiff image credit:
# "National Optical Astronomy Observatory/
# Association of Universities for Research in Astronomy/
# National Science Foundation"
#
Nebula "NGC 3372" {
Mesh "ngc3372.3ds"
Axis [-0.206916 0.153726 0.966206]
Angle 154.5
Distance 8500
RA 10.7345
Dec -59.752
Radius 219
InfoURL "http://www.noao.edu/image_gallery/html/im0061.html"
}
######################
Alternatively, here's a link to a copy of this file that you can
download:
3.3.2: The STar Catalog
In the zip archive, locate the files eta-car.stc
and eta-car-130.stc.
These are "STar Catalogs". They define the incredibly bright
variable star Eta Carinae which illuminates the nebula.
eta-car-130.stc should be used with Celestia v1.3.0.
If you have a later version, like a prerelease of Celestia v1.3.1,
then you should use the file eta-car.stc.
Drag the appropriate STC file to the Celestia subdirectory
extras\addons\NGC3372\.
or you can use this copy:
# Eta Carinae -- a high luminosity irregular variable
500002 "Eta Car:HD 93308" {
RA 161.264958
Dec -59.684517
Distance 8500
SpectralType "O5Ia"
AppMag 7.0
InforURL "http://www.seds.org/messier/xtra/ngc/etacar.html"
}
Alternatively, here's a link to a copy of this file that you can
download:
Remember: if you're going to use this file with v1.3.0 of Celestia,
then you'll have to delete the starnames from the .STC file.
The quoted string "Eta Car:HD 93308" needs to be removed.
See the sidebar above in
section 2.1.
3.3.3: The 3DS Model
In the zip archive, locate the file ngc3372.3ds
This is the 3D shape model for the picture of the nebula.
Drag this 3DS model to the Celestia subdirectory
extras\addons\ngc3372\models
Alternatively, here's a link to a copy of this file that you can
download:
Note that this model doesn't define a complicated 3D shape for
the nebula itself. Instead, it's just a thin rectangular block
for holding a photograph of the nebula. To learn how to use
"billboards" to display astronomical photographs in Celestia,
please see billboard.html.
3.3.4: The Surface Texture Image
In the zip archive, locate the file ngc3372.jpg
This is a JPEG picture of the Nebula.
Drag it to the Celestia subdirectory
extras\addons\ngc3372\textures\medres\
(All image files used by models must be in the
medres directory.)
Alternatively, here's a picture of the surface texture image which
links to a copy of the texture.
![[NGC3372]](ngc3372.jpeg)
NGC 3372 (241KB)
Note that this surface texture image is an opaque picture of the Nebula and its surrounding
stars. Often artists designing deep space models for Celestia
remove the stars from the astronomical photographs of the objects.
They then provide .STC files specifying the types and locations
of many of the stars near the Nebula. The surface textures they provide
usually include an Alpha transparency channel, too, which makes the nebulosity
translucent. None of these things have been done for this simple example.
Now your directory structure should look something
like this:
![[Celestia Addon directory structure]](dir33.jpeg)
3.4: Start Celestia.
- Check to make sure you're running v1.3.0 or newer: open the "Help" menu and select
"About Celestia". A new window will open that has the name "Celestia"
and its version number
at the top-center. The version number should be 1.3.0 or greater.
If it's 1.2.n then the Nebula Addon can't work.
If you've been copying the files to the wrong Celestia directory,
you can just drag your new "Addons" directory to the right directory.
- Test to see if Celestia knows the Nebula's name.
To do this, type the following sequence of commands:
[return] (Celestia will prompt with "Target name: " )
NGC 3372[return]
(Be sure to type a space between NGC and 3372.
The name you type here must be exactly the same as is defined in
ngc3372.dsc.)
If the .DSC file is OK, then the name will appear in the upper left corner
of Celestia's window along with the distance (8500 ly). You have now
"selected" NGC 3372.
- Now, make sure galaxy rendering is enabled:
- Select the "Render" menu
- Select the "View Options" item
- In the new window:
- check (select) the Show "Galaxies" box
- also check (select) the Label "Galaxies" box
- then select the [OK] button (NOT the [x] box at the top right)
- Type the letter "
c". Celestia will turn toward the selected object.
That's NGC3372 in this case. Celestia should pause
briefly while it loads the model and its texture. When the viewpoint
finally stops turning, you should see a purple-red blotch in the middle
of the screen labeled "NGC3372" in yellow.
If there's no yellow label, then you did not manage to select the "Label Galaxies"
box. The "Show Galaxies" box probably isn't selected either. Go back
to the "Render" "View Options..." menu and make sure their boxes are
checked. You should see the label appear immediately when its box is checked.
When you click on [OK], the label will stay while the menu goes away.
If you click on [x] at the upper right, the label will go away when the
menu does because Celestia will forget the Render changes you just made.
If there is a yellow label but no purple blotch, then either you didn't
select "Show Galaxies" (type a "u" a couple of times to toggle "Show
Galaxies") or Celestia can't find the model or its
surface texture image.
Please look at
Section 6
for a list of some of the most common problems and possible
solutions.
- Then type the letter "
g". Celestia will take you to a position near the
nebula.
- Enjoy!
Contents
See also:
[back to Contents]
A.0 Appendices.
![[Celestia Addon directory structure]](dir32.jpeg)
![[NGC3372]](ngc3372.jpg)
![[Earth in NGC 3372]](ngc3372-view.jpg)