XMoontool for X11/Motif

Here you find a version of John Walker's classical moontool. Originally written as a SunView application in 1987, the code was put into the public domain so that several variants of this software can be found on the Internet. Especially, in 1993 it was ported to X11/Motif and made available for Linux as xmoontool 3.0.1 by Cary Sandvig. What you can download below is a revised and slightly modified version of this port. The current release is named xmoontool 3.0.3.

Compared to the 1993 version the most notable changes are as follows:

v3.0.1a
- The Julian date is displayed accordant with the astronomical standard.
- The phase times (new and full moon, first and last quarter) are shown in local time.
- Color mode is enabled by default.
v3.0.2
- "Age of moon" has been fixed and returns the time elapsed in the current lunation.
- The colored moon is depicted completely darkened for several hours when new.
v3.0.3
- Introducing refined methods for reckoning celestial positions (cf. section XMoontool enhanced below).
- Option `-U` added to have distances expressed in miles rather than kilometers.

See a sample screenshot how it comes out for Nome, Alaska.

XMoontool enhanced

While the phase information given by the original program is fairly correct, this cannot generally be stated for the lunar and solar distances. With v3.0.3 an effort has been made to establish an improvement in this respect. There are now two different computational models offered to accomplish this task:

(a) The internal model: A low accuracy replacement of the original formulae, taking a few more perturbations of the moon's orbit into account. Aside from giving moderately better results, this approach has a detailed online documentation as it is derived from the description in Paul Schlyter's tutorial on computing planetary positions. (Paul Schlyter's home page stjarnhimlen.se is besides an excellent starting point for folks who wish to learn more on related astronomical topics.)
(b) The libnova model: A high accuracy approach with error bounds even acceptable for serious astronomical purposes. If you need to manually download libnova, get it here. It should be mentioned that the libnova code contains a number of GNU extensions, and building the library might require some patching on systems whose libc is not GNU. Anyway, if you are in trouble with libnova or just don't care about the moon's exact distance and visual size, you can safely choose alternative (a). As far as the lunar phases are concerned you won't experience much difference.

The decision which model to use is to be made when building the xmoontool binary. If "WITHOUT_LIBNOVA=yes" is set in the build environment then (a) is chosen, otherwise (b) is assumed; see the installation instructions for further details.

Installation Notes

FreeBSD users are referred to the ports collection or may install a binary package via `pkg_add -r xmoontool`.

For other flavors of Unix you can download the source code, extract the gzipped archive, and use `make` to build the executable. Also see the README for the complete installation instructions.
Be reminded that, aside from the X11 libraries, the Motif toolkit is required to build and run this software. At least one of open-motif or lesstif appears to be shipped with virtually every contemporary software collection for Unix-like operating systems. Ensure to have a corresponding package installed prior to executing `make`.