This Addon was created from a spreadsheet of Milky Way objects provided by Kevin Jardine. See http://galaxymap.org/
This version (v2) of the update disables the DSC catalogs and instead uses scripts to mark the objects. This provides significantly better performance.
Restore this Zip file into your "extras" or "Addons" directory. This should create the directory "galaxy_map" containing this documentation, its Catalog files, scripts, models, textures and source directory.
The catalogs and scripts show 8978 objects in 4 categories. Of the 9041 objects in the original spreadsheet, 63 nebulae do not have valid distances and are not shown. They are in the spreadsheet because Kevin has pictures of them on his Web site.
A separate script is provided for each of the categories. If you select (double-click-on) these scripts, you'll see the following:
| milky-way-cl.cel | 1013 clusters of stars represented by blue circles |
| milky-way-co.cel | 1899 molecular clouds represented by green circles |
| milky-way-hii.cel | 901 nebulae (mostly HII regions) represented by red circles |
| milky-way-st.cel | 5165 stars represented by white circles. Many of these stars are far beyond Celestia's 16KLY star distance limit, including a few Wolf-Rayet stars at the galactic center. |
| unmark-all.cel | removes all marks |
| markSol.cel | displays the location of our Sun |
STC Star catalogs are used to define the objects' locations so the scripts have objects to mark. Stars are drawn efficiently by Celestia, but have the problem that these objects cannot easily be selected or labeled because of the distances to them. All of these objects, including the stars, all are arbitrarily classed as M9. No luminosity or spectral information is provided in the spreadsheet used to create the catalogs.
DSC Nebula objects are not (yet?) handled efficiently by Celestia, so the DSC catalog files included here have been disabled by appending the letters "NO" to their filetypes. This causes Celestia to ignore them. If you enable the DSC catalogs, you'll be able to select the objects and see their labels.
A separate DSC catalog file is provided for each of the four categories. If you enable these Catalogs by removing "NO" from their filetypes, you'll see the following:
| milky-way-cl.dsc | 1013 clusters represented using the blue spherical model "cl.cmod" |
| milky-way-co.dsc | 1899 molecular clouds represented using the green model "co.cmod" |
| milky-way-hii.dsc | 901 nebulae (mostly HII regions) represented using the red model "hii.cmod" |
| milky-way-st.dsc | 5165 stars represented using the white model "st.cmod" Many of these stars are far beyond Celestia's 16KLY star distance limit, including a few Wolf-Rayet stars at the galactic center. |
All of the DSC models are translucent, since some of the objects are inside others. No attempt has been made to display the actual shapes of any of these objects. All of the models are spherical.
The star models are drawn with a radius of 50 ly just to make them readily visible from a distance. Some of these stars already are included in Celestia, but some are not. Of course, Celestia defines the locations of many stars, which it shows as points.
Celestia does not (yet?) provide a way to select different Nebula object types to be displayed at runtime. However, you can change the filetypes of the catalogs that you do not want to see so that Celestia won't recognize them when it starts up. I usually disable catalogs by appending the letters NO to the filetype. That way Celestia doesn't recognize them and it's obvious which catalogs I've disabled.
Here are a few viewpoints to display these objects in Celestia. Note that these URLs work best in Celestia v1.5.0. Celestia v1.4.1 provides only a generic galaxy model, while v1.5.0 has one based on recent surveys of the Milky Way.
Although Kevin thinks that the currently available surveys of individual galactic objects provide poor evidence for a spiral structure, I was pleasantly surprised at the good match between his catalog and the spiral structure represented by the model of the Milky Way that is provided with Celestia v1.5.0.
The contents of this Addon are copyright © 2006, Kevin Jardine & Selden Ball. All rights reserved. This Addon may be freely redistributed for educational purposes. It may not be used for commercial advantage without the written permission of the authors.