XEphem/Site/faq.html

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<TITLE>XEphem FAQ</TITLE>
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<H2>XEphem Frequently Asked Questions and Answers
</H2>
<H3>
Last updated December 29 , 2017
</H3>
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<blockquote>
<font size="+1"><b>The questions are organized into the follow categories:</b></font>
<p>
<table>
<tr>
<td width="30">
<td><a href="#UNIX">UNIX</a>
<td>getting XEphem up and running well on your UNIX (or Linux, etc) system.
<tr>
<td>
<td><a href="#Mac">Mac</a>
<td>ditto for MacOS X
<tr>
<td>
<td><a href="#Usage">Usage</a>
<td>tips, techniques and issues applicable to all platforms.
<tr>
<td>
<td><a href="#bugs">Bugs</a>
<td>Known bugs in the current release.
</table>
<P>
Can't find your question here? Try the
<a target="_blank" href="https://groups.io/g/xephem">Forum (off site)</a>
or send an email to
<a href="mailto:xephem@ClearSkyInstitute.com?subject=XEphem%20inFAQ">
xephem@ClearSkyInstitute.com</a>
<p>
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<HR>
<font size="+1">
<a name="UNIX"><b>UNIX Installation Questions</b></a>
</font>
<ol>
<p><li>
<b>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?
</b>
<p>
<p><li>
<b>When I try to use Help I get the message "Error: No running window
found". I have
<span style="font-family: monospace;">Help &raquo; Configure </span>
set to mozilla. What's going on?
</b>
<p>
Try using firefox instead as follows:
<pre>
firefox --new-tab '%s'
</pre>
(contributed by <a href="mailto:nick@ukfsn.org">Nick Warne</a>)
<p><li>
<b>
When I open Sky View I get the message "can not find classicfigs.csf" and
XEphem dies.
<br>
Or when I start XEphem I know there is supposed to be a logo
at the top but it is missing.
<br>
Or I can only find a few database files after I installed the commerical version.
<br>What's going on??
</b>
<p>
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 <code>$HOME/.xephem</code> and <code>.</code> (where
"<code>$HOME</code>" refers to the directory you are in when you first log
into your system and "dot" is UNIX parlance for the current directory),
respectively.
<p>
You can set a different value for XEphem.PrivateDir in the file named
<code>$HOME/.xephemrc</code>. For example, to use the directory
<code>/home/myhome/.myxephem</code>
for your private files add a line to this file as follows:
<pre>
XEphem.PrivateDir: /home/mylogin/.myxephem
</pre>
<p>
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
<code>/etc/XEphem</code>, and on other UNIX systems it is often
<code>/usr/lib/X11/app-defaults/XEphem</code>.
For example, to use the directory <code>/usr/local/xephem</code> for your
shared files add a line as follows:
<pre>
XEphem.ShareDir: /usr/local/xephem
</pre>
Now, to get back to the opening questions. The missing files in question
are located in the directories named <code>auxil</code> or
<code>catalogs</code> 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.
<p><li>
<b>I am running Linux and I get
errors about missing motif or X11 stuff. What can I do?
</b>
<p>
In short, you need to install more packages. For example, on Ubuntu 12.10, type
the following command to install them:
<pre>
sudo apt-get install libmotif-dev libx11-dev libxmu-dev libxp-dev libxt-dev x11proto-print-dev
</pre>
It's easier on OpenSUSE, because it brings in everything else for you as
dependencies of openmotif:
<pre>
$ sudo zypper install openmotif-devel
</pre>
On Fedora 8, it is also just as simple:
<pre>
$ sudo yum install openmotif-devel
</pre>
On Ubuntu 64 bit, use the package manager to install <b>libmotif4</b>. To install disk2 and disk3,
install <b>tcsh</b>.
<p>
On Ubuntu 16.04, try
<pre>
apt-get install libmotif-dev libxmu-dev
</pre>
<p>
On Ubuntu and Debian you may also need to add the PPA for libXp. Further information is
available <a target="_blank" href="https://launchpad.net/~zeehio/+archive/ubuntu/libxp">here</a>.
<p>
If these packages still do not resolve all references, you can try using your
package management tools to search for the package that defines a missing file.
For example, on Ubuntu you can get apt-file as follows:
<pre>
sudo apt-get install apt-file
sudo apt-file update
</pre>
Then you can search for missing file x using
<pre>
apt-file search x
</pre>
<p>
Comparable packages and package management tools are provided on other
linux flavors.
<p><li>
<b>Can I use Google Chrome as the help system browser?
</b>
<p>
Yes. Open Help &raquo; Configure help
then make and select an entry that contains the following:
<blockquote>
<span style="font-family: monospace;">
google-chrome %s
</span>
</blockquote>
Test it. If it works, make it the default using Preferences &raquo; Save &raquo; Save now.
</ol>
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<HR>
<font size="+1">
<a name="Mac"><b>MacOS X Installation Questions</b></a>
</font>
<ol>
<p><li>
<b>When I try to run the commercial version on Yosemite, I get an error about some library not being loaded. Any ideas?</b>
<p>
Yes. This is because Yosemite moved the location of the X Windows libraries.
The cure is very simple. Open a Terminal and type the following command and then XEphem will run fine:
<pre>
sudo ln -s /opt/X11 /usr
</pre>
<p><li>
<b>When I try to build the free version on Yosemite using the instructions in the INSTALL file, I
get errors about not finding X11 files. Any ideas?</b>
<p>
Yes. The change above will also cure this issue.
<p><li>
<b>I am having problems installing on Leopard and Lion. Any ideas?</b>
<p>
Follow these steps to install the CD images on Leopard (10.5), Snow
Leopard (10.6) and Lion (10.7):
<p></p>
<table border="1">
<tr>
<th>Step<th>Do this<th>Comments
<tr>
<td>1<td>Install Disk 1 package<td>If it says it was Successful, proceed to Step 2. If it almost
completes but then says it failed go to Step 1b.
<tr>
<td>1b<td>Start Terminal and type <i>exactly</i> the following at the
prompt <i>all on one line</i>:
<br><code>sudo sh -c "echo XEphem.ShareDir:/usr/local/xephem > /etc/XEphem" </code>
<td>
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).
Proceed with Step 2.
<tr>
<td>2<td>Install Disk 2 package<td>It will say it completed successfully,
which it did.
<tr>
<td>3<td>Install Disk 3 package<td>It will say it completed successfully,
which it did but along the way it wiped out Disk 2.
<tr>
<td>4<td>Install Disk 2 package (yes, again!)<td>It will say it completed
successfully, which it did and it also did not effect Disk 3.
</table>
<p><li>
<b>I am having problems installing on Mountain Lion. Any ideas?</b>
<p>
Follow these steps to install the CD images on Mountain Lion (10.8):
<p></p>
<table border="1">
<tr>
<th>Step<th>Do this<th>Comments
<tr>
<td>
1
<td>
Install Disk 1 package
<td>
If it says it was Successful, proceed to Step 2. If it almost
completes but then says it failed go to Step 1b.
<tr>
<td>
1b
<td>
Start Terminal and type <i>exactly</i> the following at the prompt <i>all on one line</i>:
<br><code>sudo sh -c "echo XEphem.ShareDir:/usr/local/xephem > /etc/XEphem" </code>
<td>
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).
Proceed with Step 2.
<tr>
<td>
2
<td>
Install Disk 2 package
<td>
It will say it completed successfully, which it did.
<tr>
<td>
3
<td>
Start a Terminal session and type <i>exactly</i> (or better yet copy/paste):
<br><code>sudo mv /usr/local/xephem/catalogs/GSC2201/*.xe3 /tmp </code>
<td>
This command moves the database files installed from Disk2 to a temporary location so the next
step does not trash them.
<tr>
<td>
4
<td>
Install Disk 3 package
<td>
It will say it completed successfully, which it did but if
Disk2 files had still been in place it would have wiped them out.
<tr>
<td>
5
<td>
Again in Terminal type <i>exactly</i>:
<br><code>sudo mv /tmp/*.xe3 /usr/local/xephem/catalogs/GSC2201</code>
<td>
This command moves the database files that came from Disk2 back where they should go.
</table>
<p><li>
<b>How can I get my trackpad or mouse to emulate a three-button mouse?
</b>
<p>
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-click is like the middle button and Command-click is like the right button.
<p><li>
<b>When I build from source I get errors like 'make: Command not found' or
about missing X11 files. Am I missing something?
</b>
<p>
Yes. You are missing XCode or X11. You can get XCode free from Apple's web site.
<p>
Note that as of
10.8 (Mountain Lion), installing XCode does not install the command line development tools. To
do that, just start XCode, open Preferences/Components and install the Command Line Tools. Also as
of Mountain Lion, Apple no longer ships X11. You now get it from
<a target="_blank" href="https://xquartz.macosforge.org">https://xquartz.macosforge.org</a>.
<p>
Now that you have command line tools such as cc and make and X11 installed, read the INSTALL
file inside the XEphem tarball for the proper way to invoke the
<b>make</b> command when building on OS X.
<p><li>
<b>Can I use my default browser as the help system browser?
</b>
<p>
Yes. To use your default browser for XEphem help on Mac OS X, enter
and select the following entry in Help &raquo; Configure help (contributed
by <a href="mailto:gavin@umich.edu">Gavin Eadie</a>)
<blockquote>
<span style="font-family: monospace;">
osascript -e 'open location "%s"'
</span>
</blockquote>
<p><li>
<b>I have created a file (such as a print, plot, list, etc) and would like
to see it outside XEphem but I can not find it. Where are they stored on OS X?
</b>
<p>
They are stored wherever your XEphem.PrivateDir resource is set. By default,
on OS X this is ~/Library/XEphem. Note you can see the Library folder
within Finder by clicking on the Go menu while holding down the Option key.
</ol>
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<HR>
<font size="+1">
<a name="Usage"><b>Usage Questions (applicable to all platforms)</b></a>
</font>
<ol>
<! ------------------------------------------------------------------------- >
<p>
<li><b>What's wrong with Help?</b>
<p>
It's probably not configured correctly. XEphem uses your Internet browser to
display help, so it has to know how to talk to it.
<p>
Off the Main window, open
<span style="font-family: monospace;">Help &raquo; Configure help</span>.
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.
<p>
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.
<p>
After you have it working, be sure to save the new configuration using
<span style="font-family: monospace;">Preferences &raquo; Save</span> or
you'll have to do it again each time you start XEphem.
<p>
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
<a href="mailto:xephem@clearskyinstitute.com">xephem@clearskyinstitute.com</a>
and we will post here for others to find.
<p>
<p>
<li><b>Why does the Sky View Grid toolbar button act so weird?</b>
<p>
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:
<table>
<tr valign="middle">
<td size="100"></td>
<td><img width="26" height="26" src="coordsysbutton.gif"></td>
<td>
toggles Display coordinate system between RA/Dec and Alt/Az, but
never changes the coordinate system for the Grid.
</tr>
<tr valign="middle">
<td></td>
<td><img width="26" height="26" src="gridbutton.gif"></td>
<td>
turns the Grid off and on, <em> and when
it turns it on always sets the Grid coordinate system to match that
currently used for Display</em>.
</tr>
</table>
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).
<p>
<li><b>Why do Sky View grid lines have a small bump to them sometimes?</b>
<p>
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.
<p>
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
<em>as seen from your location under all that air</em>, 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&#176; down from the zenith -- bonus!
<p>
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.
<P>
What happens below the horizon? This is a bit problematic. In accord with
standard models, XEphem gradually reduces refraction so that at about 5&#176;
below the airless horizon the effect is gone and the grids return to their
airless paths.
<p>
<li><b>What is the meaning of the red circles drawn on my sky chart at a
certain point on the ecliptic?</b>
<p>
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
<span style="font-family: monospace;">Preferences &raquo; Equatorial</span>
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.
<p>
If the moon is within the small circle you have a total lunar-eclipse; try
2003-11-09 @ 01:00:00 UTC.
<p>
<li><b>May I use screen shots, Postscript files, listings or other stuff made
using XEphem on my web site or publications?</b>
<p>
Regarding web sites, yes you may provided the following bit of HTML is
placed somewhere on each such page:
<p>
<pre>
&lt;a target="csiwin" href="https://xephem.github.io/XEphem/Site/xephem.html"&gt;Created using &lt;b&gt;XEphem&lt;/b&gt;&lt;/a&gt;
</pre>
<p>
It should look and work like this:
<a target="csiwin" href="https://xephem.github.io/XEphem/Site/xephem.html">
Created using <b>XEphem</b></a>.
<p>
Regarding publications, the Postscript files generated by XEphem already
contain sufficient boilerplate with regards to giving us due credit. If
these files are used intact as generated by XEphem, no further credits
are required.
<p>
What you may <em>not</em> do is cite 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.
<p>
<li><b>Why do you use Motif? Will you ever change to something else?</b>
<p>
I suspect XEphem will forever be written in Motif for the following reasons:
<ol>
<li> 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.
<p>
<li> 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.
<p>
<li> 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.
<p>
<li> 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.
<p>
<li> 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.
</ol>
</ol>
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<font size="+1">
<a name="bugs"><b>Known bugs</b></a>
</font>
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