Are provided extras used?

[Goonster]

I was just looking through all of the textures that come with Celestia when you originally download it . I was just wandering if these are already being used or if they are there to be added on if you want to ? Also when I try to open a file I am told to choose a program to open it with or go on to the web . What would you recommend? Lastly , with a couple of files labelled libpng1.dll and zlib.dll I get a warning that they open an application extension and editing or modifying them could damage the operating system , so I stop there. What is in these files and could they really do some harm ?
Sorry to ask so many questions all at once but being a newbie I do not want to do something that will cause problems I can`t solve . Any advice would be appreciated . Thanks .

[selden]

I was just looking through all of the textures that come with Celestia when you originally download it . I was just wandering if these are already being used or if they are there to be added on if you want to ?

Yes. Such modifications are called Addons. You might consider visiting http://celestiamotherlode.net/ which has a few.

Also when I try to open a file I am told to choose a program to open it with or go on to the web . What would you recommend?

Celestia's catalog files (.ssc, stc, dsc) are plain text files. Open them with Notepad or Wordpad.

Lastly , with a couple of files labelled libpng1.dll and zlib.dll I get a warning that they open an application extension and editing or modifying them could damage the operating system , so I stop there. What is in these files and could they really do some harm ?

Those are shared program libraries (Dynamically Linked Libraries) used by Windows to convert PNG images into a picture (libpng1.dll) or to decompress a binary file (zilib.dll). Viewing those files won't accomplish much unless you're debugging software that uses them. In that case you'd do better to get the source code from their Web sites.

Sorry to ask so many questions all at once but being a newbie I do not want to do something that will cause problems I can`t solve . Any advice would be appreciated . Thanks .

You probably should consider reading http://www.lepp.cornell.edu/~seb/celest ... intro.html
and
http://www.lepp.cornell.edu/~seb/celestia/textures.html
They'll provide some more details.

[Goonster]

Thanks for all the advice . I know all about the add ons and what they are . I`m just trying to learn how to use them properly . This will be a great help .