# GNOME Lunar Clock User's Guide

Copyright © 2000 by Josh Buhl

# GNOME Lunar Clock

`GNOME Lunar Clock`, shown in Figure 1, displays the current phase of the Moon as an applet for the gnome panel. To add this applet to a Panel, right-click on the Panel and choose Panel->Add to panel->Applet->Clocks->GNOME Lunar Clock.

Figure 1. GNOME Lunar Clock Applet: shown left using a real image and right using a cartoon image of the moon.

## Usage

| Your geographic coordinates need to be properly set and your computer clock must maintain accurate time in order for correct moon data to be displayed. See `Properties` below to set your geographic coordinates and consider using the ntpdate package to set the computer clock if you have internet access.

Clicking on the applet displays astronomical data pertaining to the moon including:

- Clock Functions

  - Local Standard Time -- This is the regular `wall clock' time. It's set from your computer's clock and all other calculations are based on it, so it needs to be correct in order for the data to be accurate.

  - Local Apparent Time -- The time a sundial displays.

  - Local Mean Time -- The average sundial time. It's calculated by adjusting Local Apparent Time by the equation of time and is equal to Local Standard Time corrected for your Longitude and without daylight savings time. If your longitude is a multiple of 15 degrees, your Local Mean Time is the same as Local Standard Time (without daylight savings.)

  - Local Sidereal Time -- This is the local `star time'. It's the local hour angle of the vernal equinox. `Midnight' in Local Sidereal Time means the point in the sky where the sun is on the vernal equinox just transited your local meridian.

  - Greenwich Mean Time -- Universal Time, the standard. It's also the Local Mean Time for people living on zero degrees longitude (e.g. in Greenwich :^), and their Local Standard Time when they're not on daylight savings.

- Moon's Appearance

  - Moon's Age -- The current age of the moon in days. A new moon is zero days old.

  - Fraction of Cycle -- The percentage of the current cycle the moon has completed.

  - Current Illumination -- The percentage of the visible surface of the moon which is currently illuminated.

  - Above Horizon -- Whether or not the moon is currently above the horizon at your geographic location. It's value depends upon your geographic location (see `Properties`).

- Moon rise and set times -- for yesterday, today, and tomorrow. The rise and set times for your geographic location for yesterday, today, and tomorrow are shown. It's value depends upon your geographic location (see `Properties`).

- Moon's Coordinates

  - Right Ascension -- Coordinate of the moon analogous to longitude. It's the hour angle of the moon measured with respect to the vernal equinox.

  - Declination -- Coordinate of the moon analogous to latitude. It's measured in degrees above (positive) or below (negative) the plane of the celestial equator, the projection of the earth's equator onto the sky.

  - Azimuth -- Local coordinate of the moon measured in degrees clockwise from north. It's value depends upon your geographic location. (see `Properties`).

  - Altitude -- Local coordinate of the moon meased in degrees above (positive) or below (negative) your horizon. It's value depends upon your geographic location. (see `Properties`).

  - Distance from the earth -- measured in units of radius of the earth.

Right-clicking on the applet brings up a menu containing the following items:

- Properties… — opens the `Properties` dialog.

- Help — displays this document.

- About… — shows basic information about `GNOME Lunar Clock Applet`, including the applet's version and the author's name.

## Customization

You can customize `GNOME Lunar Clock` applet by right-clicking on it and choosing Properties…. This will open the Properties dialog(shown in Figure 2), which allows you to change various settings.

Figure 2. Properties dialog showing moon image tab

The Properties dialogue is divided in two sections; one for moon image options and one for setting your geographic location.

In the `Moon Image` tab you can select the moon image to be displayed in the Panel .

| Be sure to set the correct value for the number of frames in the properties box when you select a new image file. Currently, there is a cartoon image file has 12 frames and a real image file with 60 frames available.

In the `Location` tab, shown in Figure 3 you can set the coordinates for your geographic location. Latitude degrees north are positive, south negative. Longitude degrees west are positive, east negative.

Figure 3. Properties dialog showing location tab

After you have made all the changes you want, click on OK to apply the changes and close the Properties dialog. To cancel the changes and return to previous values, click the Cancel button.

## Authors

`GNOME Lunar Clock` was written by Josh Buhl (`<jbuhl@users.sourceforge.net>`), based on wmMoonClock by Mike Henderson and the Wanda the Fish applet by George Lebl. The cartoon moon image was created by Nissen.

## License

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

A copy of the GNU General Public License is included as an appendix to the GNOME Users Guide. You may also obtain a copy of the GNU General Public License from the Free Software Foundation by visiting their Web site or by writing to

Free Software Foundation, Inc.
59 Temple Place - Suite 330
Boston, MA 02111-1307
USA