Palm Globe, version 1.10 13 Nov 1998
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The Effects menu

The View menu is used to choose the lighting effects (sunlight or not), shading, and the twilight setting. It lists the following choices:

Set lighting...
Opens the Lighting dialog which lets you choose how the globe is lit.

Set twilight...
Opens the Twilight dialog which lets you choose how the twilight band is shown. This dialog can also be opened directly from the Lighting dialog.

The Lighting dialog

The Lighting dialog lets you choose how the drawing of the globe is lit. It has three checkboxes, which take effect when the Done button is tapped:

Chooses 'sun lighting' of the globe. This lets you see at a glance which parts of the world are in daylight, and which are in the dark. This lighting is (of course) time dependent, so Palm Globe needs to know the correct time of day and your time zone in order to show the sunlight correctly.

If Sunlight is selected, the globe will normally be redrawn at regular intervals, as selected from the Other settings dialog, showing how the sunlight moves across the earth. The section on accuracy gives more details.

When Sunlight is selected, the dark side of the earth appears completely black. To make this more interesting, the Starlight choice makes the land masses on the dark side visible as a dark grey mottled pattern (if you cannot see them, try adjusting the contrast of your display).

Starlight is only meaningful if Sunlight is selected, so the checkboxes are coupled (selecting Starlight will also select Sunlight, etc.).

This choice adds shading, to give the globe a 'three-dimensional' (3-D) appearance. On the low-resolution Palm screen, this inevitably gives a rather grainy and mottled appearance -- in particular, the details of land and water boundaries may be obscured. However, the shading does convey the roundness of the earth better than the flat lighting, and the position of the sun becomes more obvious.

If 3-D is selected without selecting Sunlight, artificial lighting from the front and top left of the globe is supplied.

If none of the three choices are checked, then 'flat' lighting, as though for a map, is used; all land masses are equally visible.

The Twilight button is available as a convenience; it opens the Twilight dialog, which lets you choose how the twilight band is shown on the globe, without having to leave the Lighting dialog first.

At any time, the Undo button may be used to revert the checkboxes to the values they had when the dialog was entered.

The Twilight dialog

The Twilight dialog lets you choose how the twilight band is shown on the globe, when Sunlight is in effect.

The sun is not a point source of light, and the atmosphere scatters its light, too. Therefore, sunlight is seen on the dark side of the earth for some time before the sun rises and for some time after it sets. You can select to see all, part, or none of this twilight band on the globe.

The twilight band, when shown, is normally shown bright, or is shaded if 3-D is selected.[1]  Beyond the selected band, the earth is shown as dark.

You may choose any one of the twilight settings; the one chosen takes effect when the Done button is tapped:

Theoretical sunrise/set
This setting lights the earth as though by a point source at the center of the sun; the sunrise/set line is shown as though light ceased when the center of the sun crossed the horizon, and so no twilight can be seen; exactly half the globe is lit.

Ideal sunrise/set
This is a practical and generally accepted definition of sunrise and sunset (fifty minutes of angle after the theoretical sunrise/set) which allows for the diameter of the sun and common atmospheric effects. The line seen on the globe joins the points at which the disc of the sun will have just disappeared or be just about to appear, and encloses a very narrow band of twilight.

Civil twilight
This setting marks the end of 'civil twilight' -- a convenient point used for legal purposes (for example, when it is too dark to carry out certain tasks). Please note that Palm Globe's rendering of this line must not be used for any critical or legal decisions; errors and bugs are always possible, and the definition used by Palm Globe (six degrees after the theoretical sunrise/set) may not match the legal definition used in your country.

Naval twilight
This setting indicates the points where it is dark for all practical purposes: the center of the sun is twelve degrees below the horizon.

Astronomical twilight
With this setting, there is no sharp boundary; with shading, light fades to zero, where it is perfectly dark. At this point on the surface no effects from sunlight can be detected, and the center of the sun is eighteen degrees below the horizon.

At any time, the Undo button may be used to revert the checkboxes to the values they had when the dialog was entered.

[1] Shading may appear mottled or granular on low-resolution devices.

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Copyright (c) IBM Corporation, 1998. All rights reserved. ©
Author: Mike Cowlishaw,