1 XEPHEM An interactive astronomical ephemeris for X Syntax: $ xephem 2 Description Xephem version 2.7.1 is an interactive astronomical ephemeris program for X Windows systems. It ... o computes heliocentric, geocentric and topocentric information for celestial objects; o has built-in support for all planets; the moons of Jupiter, Saturn and Earth; and Mars' central meridian longitude; o supports user-defined objects in heliocentric or Earth orbit; o comes with sample databases of over 20,000 objects in the release kit; o can access the Hubble Guide Star Catalog from CD-ROM using gscdbd; o can quickly locate all pairs of objects which are closer than a specified maximum; o displays data in configurable tabular forms and in several detailed graphical formats; o can plot and list all data fields to disk files; o can be programmed to search for arbitrary circumstances; o can serve as the control point for robot telescopes in real-time via named streams pipes (UNIX fifos). 2 Getting Started Xephem contains extensive context-sensitive on-line help. Virtually none of that help is duplicated here so go ahead and run xephem to learn more. In order for xephem to find this help text the resource XEphem.HELPFILE must be set properly. If you are running xephem from the source directory of the distribution kit this should be set to auxil/xephem.hlp. When you first run xephem you may hear a beep. This means xephem has added a message to the message box menu. This menu is not shown by default. Whether the message box is displayed may be toggled by using the Messages entry in the File pulldown menu off the Main menu. Whether xephem beeps when it adds a message may be toggled using the Message Bell option in the Preferences pulldown menu. 2 Quick Menu Tour The Help pulldown at the top right of the main menu provides access to several categories of assistance applicable to the overall operation of xephem. Those unfamiliar with xephem might begin by reading the Introduction help section first and reading the additional help information in the order in which it is listed in the pulldown Examples for several useful operations are now included as well. The Main menu of xephem provides control and display of three basic services: observing circumstances, looping, and access to additional displays. Observing circumstances includes location, time and atmospheric conditions (used for the refraction model). Looping refers to the ability to set up xephem so that it automatically increments time at a desired step size and rate. Additional displays provide all of the tabular and graphical information available, and always refer to the circumstances defined in the main menu. These additional displays are activated from the Views pulldown. Xephem has information about the Solar system built in and can be accessed without the need to access an external database. Xephem can read files of additional objects into memory as well. Database files are read in using the Data Base button in the Objects pulldown or via the DBFIFO fifo (see the Help for the Data Base menu for more details on formats and the fifo). All of the information about each object in memory may be inspected and manipulated in detail and assigned to so-called `user defined objects' X and Y using the ObjX, ObjY button in the same pulldown. All of the data that xephem presents in numeric form may be written to a file and later plotted; written to a file as a tabular listing; or used to formulate an arbitrary mathematical expression that may be solved for a maximum, minimum or zero. These facilities are accessed from the Control pulldown. Several options related to performance and display formatting may be controlled from the Preferences pulldown. The Files pulldown in the main menu allows one to reset the main menu from the initial resource settings; toggle whether the general messages menu is displayed; and quit the program. 2 X_Resources Xephem has many X resources, some of which you will soon want to tune to your taste and circumstances; many others may be left unchanged. Look through the XEphem.ad sample distribution for full details. If no resources are available xephem contains internal fallback resources that are suitable for a black-and-white X terminal. Of course, in addition to all the custom resources, xephem supports the usual Xt command line arguments such as -display, -xrm, -synchronous, -fg and -bg. The application class of xephem is XEphem. A list of widgets in xephem would be enormous. If you really want such a list, build xephem to use the editres protocol then inspect the widget hierarchy using the standard X tool editres. The necessary code to support the editres protocol is already in xephem.c surrounded by #ifdef WANT_EDITRES. 2 Time_zones If __STDC__ was defined by the compiler when xephem was compiled and at runtime the gmtime() ANSI C function returns non-NULL, then xephem will attempt to support time zone control. The time zone name and offset is obtained from the operating system whenever the "Now" option is used from the various Main menu time fields or resources or at each time step if Auto Time Zone mode is in effect. Otherwise, xephem never attempts to automatically change the time zone name or offset. In any case, the time zone offset and name may always be set manually at any time from the Main menu, or they may be initialized from the XEphem.TZName and XEphem.TZone resources, respectively. 2 Files_and_Fifos Xephem can use and create several files and communicate via several fifos. The following table lists the name of the defining resource, the default value and a short description of each. Full details for each may be found in the appropriate run-time Help available from within xephem. Also look in the sample application defaults file, XEphem.ad, for examples of settings these and many other resources. The initial default settings define everything relative to the source tree directory of the xephem distribution kit. Many file names may begin with tilde (~) to refer to the user's HOME directory. X Resource Name Default Usage --------------- ------- ----- List*Filename.value work/ephem.lst Listing file Plot*Filename.value work/ephem.plt Plot file DBFIFO fifos/xephem_db_fifo auto database input DBdirectory edb database directory DBinitialFiles basic.edb db files auto loaded DBpattern *.edb datebase file pattern HELPFILE auxil/xephem.hlp Help text SITESFILE auxil/xephem_sites Earth view sites SKYINFIFO fifos/xephem_in_fifo Sky View aim input SKYLOCFIFO fifos/xephem_loc_fifo Sky View Button2 report SKYOUTFIFO fifos/xephem_out_fifo Sky View re-aim output 2 Author Elwood Downey, ecdowney@noao.edu. Although they graciously provide me with email and other services, neither I nor xephem are associated in any way with the National Optical Astronomical Observatory. 2 References Ephem is the ancestor of xephem. It is suitable for "dumb" 24x80 character displays, including VMS and DOS as well as UNIX. The latest version may be found on at ftp://iraf.noao.edu/contrib/xephem/ephem. The latest version of Xephem is maintained at ftp://iraf.noao.edu/contrib/xephem. Source code, the SAO catalog and several sample executables are also available near that address. A WWW page is also available at http://iraf.noao.edu/~ecdowney/xephem. The online Help entry on Credits lists some of the many texts, individuals and organizations that have contributed to xephem.