XEphem 3.7.5 Frequently Asked Questions and Answers

Last updated July 27, 2011

The questions are organized into the follow categories:

UNIX getting XEphem up and running well on your UNIX (or Linux, etc) system.
Mac ditto for MacOS X
Usage tips, techniques and issues applicable to all platforms.
Bugs Known bugs in the current release.

Can't find your question here? Try the Forum (off site) or send an email to xephem@ClearSkyInstitute.com

UNIX Installation Questions

  1. I built from the downloaded source code and I am having problems with XEphem GUI operation, such as windows not closing properly using the title bar control. Any suggestions?

    If you are using lesstif, switch to Open Motif then rebuild. You will need both the runtime and developer kits. You can also get just the minimum you need from our User Contrib page. Or just forget the hassle and do it the easy way by purchasing the CD version.

  2. When I try to use Help I get the message "Error: No running window found". I have Help » Configure set to mozilla. What's going on?

    Try using firefox instead as follows: 

        firefox --new-tab '%s'
    (contributed by Nick Warne)

  3. When I open Sky View I get the message "can not find classicfigs.csf" and XEphem dies.
    Or when I start XEphem I know there is supposed to be a logo at the top but it is missing.
    Or I can only find a few database files after I installed the commerical version.
    What's going on??

    Sounds like there is a problem with the way XEphem support files are configured. First some background. XEphem looks for support files in two places in order, first XEphem.PrivateDir then XEphem.ShareDir. These terms are X Window System resource names that refer to a per-user private directory and a system-wide shared directory, respectively. By default these are $HOME/.xephem and . (where "$HOME" refers to the directory you are in when you first log into your system and "dot" is UNIX parlance for the current directory), respectively.

    You can set a different value for XEphem.PrivateDir in the file named $HOME/.xephemrc. For example, to use the directory /home/myhome/.myxephem for your private files add a line to this file as follows: 

            XEphem.PrivateDir: /home/mylogin/.myxephem

    You can set a different value for XEphem.ShareDir using the standard X Window System resource file mechanism. The default location for the global version of this file for XEphem on Linux and MacOS X systems is /etc/XEphem, and on other UNIX systems it is often /usr/lib/X11/app-defaults/XEphem. For example, to use the directory /usr/local/xephem for your shared files add a line as follows: 

            XEphem.ShareDir: /usr/local/xephem
    Now, to get back to the opening questions. The missing files in question are located in the directories named auxil or catalogs under XEphem.ShareDir. So if these directories are not set up correctly, such as from a previous installation of XEphem that was installed differently or when trying to mix the free and commercial versions of XEphem, they will not be found. With this explanation, you now know how to check that your private and shared directories are set up as desired and then things should work correctly.

  4. I am running Linux and when I try to build from source I get errors about missing X11 stuff. What can I do?

    This question pops up often on the XEphem Forum In short, you need several more packages. For example, on Ubuntu 10.10, type the following command to install them: 

        sudo apt-get install libx11-dev libxmu-dev libxp-dev libxt-dev x11proto-print-dev
    If these packages still do not resolve all references, you can try using apt-file to search for the package that contains the missing file. You can get apt-file as follows: 
        sudo apt-get install apt-file
    sudo apt-file update
    Then you can search for missing file x using 
        apt-file search x

    Comparable packages and package management tools are provided on other linux flavors.

  5. I am running Linux and when I try to run the install script on the commercial edition it says "./install: No such file or directory". That makes no sense, because the file is right there. What's going on?

    The install script uses the #! mechanism to invoke an interpretor. The message refers to the interpretor, in this case /bin/csh. So the real problem is you don't have /bin/csh installed. Look around for a package with csh in it, get it installed, then try again. On ubuntu try: 

        sudo apt-get install tcsh

  6. I just purchased the CD and am trying to run on Ubuntu. When I start xephem it says it can not find libpng.so.3. Any ideas?

    It appears Ubuntu is shipping with several different flavors of libpng. Since xephem wants exactly libpng.so.3, the key is to try symlinks with this name pointing to the ones on your system until you find one that works. For example, after doing this command from an xterm: 

            $ ls /usr/lib/libpng*
    suppose you discover one called libpng12.so.0. Then try this command: 
            $ sudo ln -s libpng12.so.0 /usr/lib/libpng.so.3
    then xephem might work. If not, rm this symlink and try another.

  7. Can I use Google Chrome as the help system browser?

    Yes. Open Help » Configure help then make and select an entry that contains the following:

    google-chrome %s
    Test it. If it works, make it the default using Preferences » Save » Save now.
MacOS X Installation Questions

  1. I am having problems installing on Leopard and Lion. Any ideas?

    Follow these steps to install the CD images on Leopard (10.5), Snow Leopard (10.6) and Lion (10.7):

    StepDo thisComments
    1Install Disk 1 packageIf it almost completes then says it failed go to Step 1b, otherwise go on to Step 2.
    1bStart Terminal and type exactly the following at the prompt all on one line:
    sudo sh -c "echo XEphem.ShareDir:/usr/local/xephem > /etc/XEphem"     		This creates a file telling XEphem where its supporting files are installed. This must be done as root which the command "sudo" does temporarily -- admin is not enough (this is why the install fails).
    2Install Disk 2 packageIt will say it completed successfully, which it did.
    3Install Disk 3 packageIt will say it completed successfully, which it did but along the way it wiped out Disk 2.
    4Install Disk 2 package (yes, again!)It will say it completed successfully, which it did and it also did not effect Disk 3.
    5 Start XEphem from Finder at /Applications/XEphem.app Or start from Terminal by just typing "xephem".

  2. How can I get my trackpad to emulate a three-button mouse?

    Start XEphem, then click on the big X app in the dock. Open X11 -> Preferences. In the Input tab, check on "Emulate three button mouse". Now Option-tap is like the middle button and Command-tap is like the right button.

  3. When I build from source I get errors like 'make: Command not found' or about missing X11 files. Am I missing something?

    Yes. Xcode. You can get it free from Apple's developer web site.

    Then read the INSTALL file inside the XEphem tarball for the proper way to invoke the make command when building on OS X.

  4. Can I use Firefox as the help system browser?

    Yes. To use the Firefox browser for the XEphem help system on Mac OS X, enter and select the following entry in Help » Configure help (contributed by David Radunsky)

    osascript -e 'tell application "Firefox-bin"' -e 'get URL "%s"' -e 'end tell'

  5. Can I use my default browser as the help system browser?

    Yes. To use your default browser for XEphem help on Mac OS X, enter and select the following entry in Help » Configure help (contributed by Gavin Eadie)

    osascript -e 'open location "%s"'
Usage Questions (applicable to all platforms)

  1. What's wrong with Help?

    It's probably not configured correctly. XEphem uses your Internet browser to display help, so it has to know how to talk to it.

    Off the Main window, open Help » Configure help. Look through the choices for your browser. If you find it, just click the button on the left and test with any XEphem Help entry. Note that some of these commands assume the browser is already open and do not work otherwise, so if the line for your browser is listed and activated but Help still does not work, try opening your browser first and trying again.

    If Help still does not work, you'll have to figure out the command to issue to your browser to open a local file. The table entry is passed to a shell so you can do whatever you need to, but don't forget to quote sensitive characters. Enter your new command in any line of the table, using %s where the local file name should go, then click to activate the line and test again.

    After you have it working, be sure to save the new configuration using Preferences » Save or you'll have to do it again each time you start XEphem.

    We researched several browsers but there are certainly more we didn't try, and there might well be better ways to talk to them than we found. Please send your suggested commands to us at xephem@clearskyinstitute.com and we will post here for others to find.

  2. Why does the Sky View Grid toolbar button act so weird?

    Perhaps the logic is only obvious 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 rules for the control buttons are as follows:
    toggles Display coordinate system between RA/Dec and Alt/Az, but never changes the coordinate system for the Grid.
    turns the Grid off and on, and when it turns it on always sets the Grid coordinate system to match that currently used for Display.
    In this way 6 combinations of coordinate systems (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).

  3. Why do Sky View grid lines have a small bump to them sometimes?

    Because of atmospheric refraction. Refraction raises everything to a greater extent as you look lower and lower, increasing rapidly near the end to about 32' at horizontal. This effect is evident when displaying in one (ideal) coordinate system and overlaying (refracted) grid lines in the opposite coordinate system.

    Suppose you are pointing near the horizon, are using Alt-Az display mode and are displaying RA-Dec grid lines. When projected onto the celestial sphere as seen from your location under all that air, this has the effect of curving the grid lines a little higher in the vicinity of the horizon than one would see without refraction. Indeed, because of refraction you actually see about 32' more than 90° down from the zenith -- bonus!

    Demonstrate this to yourself by going to the Main window and setting an Air Pressure value of 0 to effectively eliminate refraction. You will see the grid lines straighten out, and objects that were visible slightly above the horizon will drop below and go out of site.

    What happens below the horizon? This is a bit problematic. In accord with standard models, XEphem gradually reduces refraction so that at about 5° below the airless horizon the effect is gone and the grids return to their airless paths.

  4. What is the meaning of the red circles drawn on my sky chart at a certain point on the ecliptic?

    The anti-solar point is marked with a small open circle. The edges of the umbral and penumbral Earth shadow are marked with larger open circles. If Preferences » Equatorial is set to Topocentric, the projection is at the current distance of the Moon and corrected for parallax; if set to Geocentric the projection is at infinity.

    If the moon is within the small circle you have a total lunar-eclipse; try 2003-11-09 @ 01:00:00 UTC.

  5. May I use screen shots, Postscript files, listings or other stuff made using XEphem on my web site or publications?

    Regarding web sites, yes you may provided the following bit of HTML is placed somewhere on each such page: 

        <a target="csiwin" href="http://www.ClearSkyInstitute.com/xephem/xephem.html">Created using <b>XEphem</b></a>

    It should look and work like this: Created using XEphem.

    Regarding publications, the Postscript files generated by XEphem already contain sufficient boilerplate with regards to giving us due credit. If these files are used in tact as generated by XEphem, no further credits are required.

    What you may not do is site isolated numbers that you pulled off XEphem in your publications. There are too many contextual circumstances surrounding astrometric quantities to make fair representation of all that XEphem considered in its computation of displayed values.

  6. Why do you use Motif? Will you ever change to something else?

    I suspect XEphem will forever be written in Motif for the following reasons:

    1. First and foremost, I very deliberately make the decision to focus my time and energy on features and accuracy, not aesthetics because, frankly, it's the aspect of the project I enjoy the most. I still have a long list of features to add in the coming years; this effort, and my enjoyment, would be drastically diluted by a major effort to change the L&F.

    2. The effort to change widget sets would be large. Not only is it "just" a matter of changing widgets in roughly 100k lines of GUI code, but I make deep use of Motif-specific functionality (after all, I was involved in creating Motif in the 80s) that do not map well to other toolkits.

    3. I know the entire API of Motif (about 3000 functions) completely by heart and am very efficient using it. When adding a new window, I see right through the widgets straight into the science. I am *almost* this proficient with Qt and Java Swing but see #2 and #4.

    4. I must have no inherent artistic or aesthetic sense of my own because, really, Motif still looks fine to me. To my mind, all buttons look alike and drag-and-drop is silly. I have no personal appreciation whatsoever of why one would pick one toolkit over another. I lived through the great SunView/OpenLook/Motif GUI wars of the late 80s wondering all along what the fuss was about.

    5. I feel no compulsion to compete or otherwise compare XEphem with any other software. It is my own labor of love which I am happy to share, it is not my intention to make it "successful" by any external measure. I do hope you find XEphem useful, even if you find it ugly.
Known bugs

  1. If you get errors when downloading asteroid data from Lowell, try editing astorb2edb.pl. Replace lines 229-236 with one line that instead of using ftp uses curl to download the file. The result should look like this: 
        # transfer
    print "Getting $ORBFTPDIR/$ORBGZFILE from $ORBSITE...\n";
    !system ("curl -s -o $ORBGZFILE ftp://$ORBSITE/$ORBFTPDIR/$ORBGZFILE") or
	die ("curl -s -o $ORBGZFILE ftp://$ORBSITE/$ORBFTPDIR/$ORBGZFILE failed");
    astorb2edb.pl is in the XEphem.ShareDir/auxil directory, which by default is /usr/local/xephem/auxil. Note you can run this script directly if desired, that's really all XEphem does to download data from Lowell.

  2. When working through the INSTALL instructions on Ubuntu 9.10, in step 3b.3 note they moved app-defaults to /etc/X11/app-defaults.