Cartes du Ciel 

Based on an anonymous post on sci.astro.amateur.

I hope I can help and not make this too confusing.

For the smaller Tycho Catalog (magnitude 11.x,) you need to download those three files for the North, Equatorial, and South regions. Run those self-disolving files and have them install to the path where you installed "Cartes du Ciel / SkyCharts". It will create all the sub-folders and files that are required. 
These files are already converted to the required format for use with "Cartes du Ciel". 
The convtyc.zip utility that is provided is to convert the original tycho catalog from a file named tyc_main.dat (350 megs) if you already own this file, otherwise it is better to download the three files mentioned above (only 18 megs).

For the larger Tycho Input Catalog (to magnitude 12.1, 3.1 millions stars) there is now a ready-to-run version of this catalog available. This would be your easiest option for obtaining and installing this catalog in a format that Cartes du Ciel can read directly. 
If on the other hand you have already downloaded the original Tycho Input Catalog files from ftp://cdsarc.u-strasbg.fr/cats/I/197A/  or if you'd rather have the original file format for archive sake, you need to take a few extra steps.You will need to have a utility that can handle .Z files (UNIX compress) archives. I used ZipMagic which handles everything so I don't know what special format these are in if any. I think I remember seeing a link that the author posted to a utility that will do this for you if you don't have ZipMagic or other software. WinZip also handles these files just fine. 
After you download those files named "TIC1.Z", "TIC2.Z", "TIC3.Z", "TIC4.Z" and "TICA.Z" from the link the author provides (above), un-archive them, keeping them in the same name but without any filename extension on them. When done unzipping them you should have 5 files on your drive in a single folder, with filenames of "TIC1", "TIC2", "TIC3", "TIC4", and "TICA". (Note there is no period or other characters after the filename, WinZip wants to add in the peroid at the end if you use this utility to uncompress them, rename them if needed). 
Now you have to run the program the author provides called "convtic.zip".  (Note the other conversion program was only different by one letter, this is for TIC (Tycho Input) catalogs, not the TYCho catalogs).  This program will go through those "TICx" files and completely rewrite them in a new database structure to another location (of your choice) into a form that "Cartes du Ciel" can read. Have about 55 megs of space handy for the (g)zip source files before and after unzipping them, and another 55 or so megs available for the final converted database files. 

In all cases, you can place these final databases on any storage medium you want, just be sure to keep their directory and filename structures intact.  Point "Cartes du Ciel"'s catalog setup options to where you have these final converted files. I have all of mine burnt onto one CD so I can save hard-drive space. (Having a friend with a CD burner is really handy about now. :-) I put the Compact GSC, both Tycho catalogs, and other large reference catalogs all on one CD. This way I can put the USNO-SA2.0 CD in one CDROM drive and my compilation CD in another drive withtout ever having to swap CD's throughout the whole 19 magnitude zoom range. Works GREAT!)

The Hubble Guide Star Catalog (GSC) is a whole other monster to deal with. Not only due to its size, but because you can use 3 different "flavors" of the GSC with Cartes du Ciel.

GSC Scenario #1:  Download the original FITS version (350 megs) in GZIP format at ftp://adc.gsfc.nasa.gov/pub/adc/superseded/1/1220/ .  Keeping the path and filename structure on your end the same as at the download site (be sure to include all files and other folders from the main starting point at .../1220/, including the sub-folders where that archive is stored, but not those folders from "above" that starting point). Your starting folder/path name need not be named "1220", but it should contain everything in that folder and below it.

Recreate the same database structure (after the ../1220/ starting point) on your end but un-gzip all those files to their new locations.  You will need approximately 350 megs free space for the gzip files, and another partition or sub-folder of approximately 1.4 gigs for the uncompressed files.  I believe it took even more space than 1.4 gigs due to how many small files are created, but it can eventually all fit on 2 CD's. 
You can choose to ungzip only those regions of the sky you really need to use, you don't have to recreate the whole database if hard-drive space is at a premium for manipulating the files.  Read those "readme" files at the archive site to see which "Nxxxx" or "Sxxxx" folders are for which latitude bands of data if you need to pick and choose before downloading. You will notice that the North and South polar database regions have fewer files in their Nxxxx or Sxxxx folders/paths than the equatorial regions do. (In case you want to eye-ball how they are named and how the directory structure is laid out.) It's easy to understand when you visualize that the equtorial bands of latitude are larger in circumfernce than the smaller, circular, polar regions.

Warning: each area of the sky is in its own separate gzip file. Each folder (of the 20 or so folders) can have ~50 to ~500+ gzip files in them. Trying to use WinZip to undo them will be a royal pain doing them one by one, but it might be the only option to you if you don't have other software or know how to use the free DOS program mentioned below. 
I used ZipMagic which allowed me to highlight all the files in one sub-folder and un-gzip them to the destination folder (of the same name elsewhere). 
The author suggests using a little DOS based utility that you can run from DOS or from a DOS window from within Windows. Get GNU Gzip from http://www.gzip.org/ . You may use it from the command line to unzip all the files in a directory with the simple command " gunzip * "

I eventually put my FITS GSC files on 2 CD's so final storage space was not an issue. I put the north database regions (bands of latitude) on one CD and the south regions on another. Astronomy software that reads these 2 CD's will prompt you for the other one if it can't find the region it is trying to read. (I tested this with the floppy disk version of Epoch2000sk and it worked just fine with this 2 CD GSC set, but Epoch2000sk did not read the Compact GSC described next.) Again, be sure to keep the main folders and files intact when burning to CD's, just leave out the Nxxxx or Sxxxx named folder regions on each CD as you see fit.

 If you cannot download 350 megs you can buy the two CD's from the ASP http://www.aspsky.org/ .

GSC Scenario #2:  (have I lost you yet?? :-)  You need to download the COMPACT GSC database from ftp://cdsarc.u-strasbg.fr/cats/I/220/ (don't confuse this with the previously mentioned gzip compressed database files, the original FITS GSC).  This is a complete GSC catalog of stars and objects, all 19+ million of them, but the data as being in a compressed format that you don't need to worry about. You just download the ~300 megs worth of files from the FTP location starting at ../220/ to your system, again, keeping all files, folders, and directory structure intact. Just as you see it from the main entry point in folder "220" of that database online. Don't forget the sub-folders where the main meat of this database is stored. Be sure to include those small BIN-DOS and BIN folders too. Some astronomy programs require them if you want to use this database with other software. Cartes du Ciel author rewrote his program so it reads this Compact GSC directly and does not require these little support files anymore, but again, other software might. Get them just in case. They're small. :-)

Cartes du Ciel reads this database just the way it is, no further conversions or tweaking is needed. Just point Cartes du Ciel's catalog preferences dialogue for the GSC-Compact file-path to where you have these files stored (on hard-drive, in sub-folder, on CD, wherever you have put them).

GSC Scenario #3:  Cartes du Ciel's author also provides for yet one more option. This can come in handy if you already own the 2 CD set of the original FITS GSC. Or if you don't have room to keep the original FITS GSC (from scenario #1) anywhere handy on your system after downloading and ungzipping. You can use the conversion program he provides, "convgsc.zip", to make its own compacted database from the 1.3 gigs worth of data (aprox. 480 megs in size when done if you convert all 1.3 gigs). He also allows you to only convert those latitudes you need to convert if you'd like to keep the database even smaller. The latest version of convgsc.zip has additionals options to remove duplicate entries and non-stellar objects. This can reduce the size down to 300 megs.

If you get the free USNO-SA2.0 catalog of stars from magnitude 16 to 19 (~54? million stars) by sending a request at http://www.nofs.navy.mil/projects/pmm/a2.html , you just use it as-is. Plop it in a CD ROM and point Cartes du Ciel to it. I have found that this database actually has many stars brighter than magnitude 16, so don't worry about the slight gap in GSC's magnitude 15.x limit and this one's claimed starting point of magnitude 16. GSC + USNO-SA2.0 catalogs seamlessly cover all magnitudes. In fact there is a small overlap. If you enable both catalogs, some stars are plotted twice near the same location if you zoom in very close. Be sure to set your catalog's field of view preferences so one turns off when the other catalog is queried if you find this to be a problem. This also happens with the other lower magnitude catalogs due to slight object position discrepancies between catalogs.

Has this helped? Hurt? I hope I've not made it more confusing. It's really easier to do than say in print. Honest. :-) There are just so many options and catalogs to play with that it can seem harder than it is.