XEphem 3.4 Frequently Asked Questions and Answers

Last updated 5 Jan 2001

  1. After installing from the CDROM, I can run XEphem just fine but when I use Preferences -> Save it says Permission denied. Did I do something wrong?

    No, there is a bug in the install script on the CDROM. It creates the directory .xephem in your home directory all right but does not change the owner to you. You can do it by hand as follows:

        $ cd
        $ su
        (your root password)
        # chown $USER ./.xephem
        # exit 
        $
    

  2. Why can't I save the Elevation setting?

    Because of a bug. To work around it add a new entry in the xephem.sit file with the desired values. If you want to actually fix the problem, rebuild XEphem after editing mainmenu.c lines 1042-1046 so ELEV_FID follows LONG_FID, like so:

            static InitMap imap[] = {
                {EPOCH_FID, "Epoch"},
                {LAT_FID,   "Lat"},
                {LONG_FID,  "Long"},
                {ELEV_FID,  "Elevation"},
    	    ...
    

  3. When I build XEphem on an Alpha with RedHat 6 why are there no stars in the Sky View?

    There is evidently a bug in the compiler's optimization passes. Remove all optimize flags (the -O's), rebuild, and it should work.

  4. Where can I get the Hipparcos and Tycho-2 catalogs and the PPM in .xe2 format?

    They are available on the CDROM edition.

  5. What is wrong if I am having GUI problems such as ...
    • bringing up just window xyz causes XEphem to bomb out?
    • I can not close window xyz properly using the abc window manager?
    • I see Warnings about XmForm?
    • some of the stuff in window xyz overlaps and I can not see it properly?

    If you are using lesstif, try changing to Open Motif (you will need both the runtime and development kits).

    If just the Jupiter, Saturn and Uranus views cause XEphem to bomb but it runs ok otherwise, it is not yet clear exactly what is wrong. However, one post to the XEphem user forum suggests it might be specific to using the Sawfish window manager in the Gnome graphical environment, and changing window managers will help.

    If these suggestions do not help, please send a detailed description to xephem@clearskyinstitute.com.

  6. What happened to XEphem.ad?

    XEphem now creates its own resource file when you use the new Preferences->Save feature. One is no longer included with the distribution. The first time you Save any settings, the directory $HOME/XEphem will be created and the file XEphem will be created there to hold the changed settings.

    The only time you might want to create a resource file manually is to set up different defaults for all XEphem users on your system. Suppose for example you put the support files someplace (the stuff in the directories auxil, fifos and catalogs) such as the directory /usr/local/xephem. Then you can make this known to all users by creating a new XEphem file and put just one line in it as follows:

        XEphem.ShareDir: /usr/local/xephem
    
    Then put this file in a place where all X programs can find it such as
        /usr/lib/X11/app-defaults/XEphem
    

    After a while if you find that all of your users are tending to save similar changes, copy the common lines that are in each of their private XEphem files into this global one, then they will be the defaults for everyone from then on (but individual users can always continue to override them with their own settings).

  7. Does the executable on the XEphem CDROM work on RedHat 7?

    Yes, but not on a pure RH7 system. Visit their bug fixes page and install the glibc and GCC fixes. Until you do, binary compatability is broken for executables built with RH6.2 (which the CD was). After these are installed, XEphem will work fine.

  8. Any ideas on why XEphem crashes when displaying with X Server xyz on Windows 95/98/2k?

    Windows X Servers come in many shapes and sizes, some are better than others. Perhaps my favorite is SCO's XVision. The almost-free MIX lacks some bells and whistles but does get the job done well enough to run XEphem.

    For more innovative approaches check out VNC and VMWare. Both of these go way beyond a simple X Server.

  9. When I build XEphem why do I see lots of errors about undefined references to symbols starting with Xp?

    With some versions of Motif (including OpenMotif) you must link with the Xp library. In the link line of your Makefile just add -lXp after -lXm. The set of X libraries ends up looking something like this:

        -lXm -lXp -lXt -lXext -lX11
    

    It is correct in the Linux section of the sample Makefile.smple included in the tar file distribution.

  10. What is going on when I start XEphem and it says something about "Version skew"?

    This means you have an older version around. In particular, look for a resource file named XEphem in places like /usr/lib/X11/app-defaults, /usr/X11R6/lib/X11/app-defaults or in your home directory. Also see if perhaps you have the environment variables XUSERFILESEARCHPATH, XFILESEARCHPATH, or the ancient APPLRESDIR set, because these can sometimes be set by X Windows startup scripts and point off to literally any place.

    The reason for this concern is XEphem 3.4 treats resource files quite differently than did 3.2.3; it does not need one initially and should only find the one it creates when you Save settings from within XEphem.

  11. Why are the positions of the asteroids not quite right?

    XEphem computes asteroid locations using static Keplarian elements, not orbital integrations. Unless they wander close to a large body the elements will remain accurate for several weeks. But eventually they must be updated. XEphem comes with two perl scripts, mpcorb2edb.pl and astorb2edb.pl, which make this easy to do. These fetch new elements from the Minor Planet Center and Lowell Observatory, respectively. Use which ever you prefer. If you have the CDROM version just run them according to the manual. If you have the free version, look in the GUI/xephem/tools directory.

    These services from MPC and Lowell are greatly appreciated.

  12. Any suggestions if XEphem crashes due to lack of colors?

    When started up XEphem tries to automatically decide whether it will need a private colormap. You can force this by adding the following command line argument:

        $ xephem -install yes
    
    If this helps, you can make the change permanent by setting the following X resource:
        XEphem.install: yes
    

    If this does not help, run xdpyinfo and see how many colors your default visual provides. XEphem requires about 150 colors to run properly, and offers no way at this time to use other than the default visual. If you discover your server provides a visual with this many colors but it is not the default, perhaps you can restart the server in a way that will make it the default. If you use a server from XFree86, investigate the -cc (see man Xserver) or -bpp (see man XFree86) options.

  13. Why am I getting unusual Dawn/Dusk times?

    The three fields (Dawn, Dusk and Night Length) always apply to the local current day. Difficulties arise when these events occur within 4 minutes of local "midnight" with respect to the time zone defined by TZ Offset. In particular, if these fields are not behaving as you would expect, check that TZ Offset is set commensurate with the current Longitude.

  14. Why would the time change by one hour just because I changed the date?

    This occurs if automatic savings time tracking is turned on and the new date is for a period which differs in regards to whether savings time is in effect. It is a feature .. but you may disable it by typing in a fixed value for either the TZ Name or TZ Offset fields in the Main menu. When automatic savings time is active, a little clock appears in the upper right corner of the Time section.

  15. Why don't my Backspace and Delete keys work correctly?

    This is likely a problem with your general X Windows setup rather than with XEphem itself. Use the X utility program xmodmap to check into your situation. For example, on many Linux systems, the problem can be solved by running the following commands before running XEphem (it will likely fix similar problems with other X programs as well):

        % xmodmap -e "keycode 22 = BackSpace"
        % xmodmap -e "keycode 107 = Delete"
    
  16. Although it seems to basically run ok, why do I see many "translation errors" and warnings when XEphem is first started?

    Another X Windows admin problem... this is caused by not having the correct version of the file XKeysymDB or not having it in the correct place (typically /usr/lib/X11). Get one from somewhere (such as here) and put it in /usr/lib/X11 or anyplace and define the environment variable XKEYSYMDB with the full path to where ever you put it.

  17. Why can't I use the PgUp or PgDown keys to browse the Help dialog?

    Because of something known as keyboard focus. Whether a newly-mapped dialog receives keyboard focus depends on your window manager. If yours does not automatically give the Help dialog focus, then try clicking the left mouse button near the vertical scroll bar once. Similarly, the Sky View scroll bars can also be operated using the PgUp/Down keys (and the Arrow keys too) but, again, only if they have the focus.

  18. What's with the Sky View Grid toolbar button? It acts weird.

    There is logic to it, but perhaps it is only clear to me! The Sky View uses two coordinate systems: RA/Dec and Alt/Az. The coordinate system for Display orientation is independent of that for the Grid. The Display orientation button toggles the display system between RA/Dec and Alt/Az, but never changes the system for the Grid. The Grid button turns the Grid off and on, and when it turns it on it always uses the same system as currently used for display. In this way 6 combinations (2 for Display [RA/Dec + Alt/Az] X 3 for Grid [RA/Dec + Alt/Az + off]) can be controlled with just 2 buttons (although one can not switch among them in an arbitrary order).

  19. My question is not here.. is there a user group for XEphem?.

    Yes. To share tips and ideas with others, visit the XEphem Forum.


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