Saturn! Version 1.2 - 2005 November 13

Saturn! computes the orientation of the rings of Saturn and its eight (8) major satellites.

Saturn! also computes and displays various information about the Earth, the Sun and Saturn, including the visual magnitude, the position angle of Saturn's rotation axis with respect to the northern celestial pole, the inclination of the rings and the light travel time and distance to Saturn.

Minimum Requirements:

• PalmOS 3 or higher.
• 256k of memory for the program and its data
• http://www.radiks.net/~rhuebner/mathlib.html (deprecated, but available from MEW3.com) MathLib.prc - a free shared math library

1. The main diagram window where Saturn and the moons are displayed.
2. An example of one of Saturn's moons.
3. Variable magnification from 0.1 to 9.9. Press MAG: to select a course magnification from 1 to 9, and then use the up and down buttons to fine tune the magnification in 0.1 increments. Use the F button to "fit to screen" all the moons.
4. The Inclination of the plane of the rings (I:), the angle of the rotational axis of Saturn (P:) and the visual magnitude of Saturn (M:) are all displayed.
5. Star Pilot's Location Manager is supported. As well as setting an offset from GMT on the preferences screen. The PalmOS built in location for PalmOS 4 or later is also supported.
6. Use the built in PalmOS date selector to choose dates.
7. Optionally, the Julian Day number can be displayed below the date.
8. The registered version of Saturn! has "quick launch" buttons that allow you to quickly start Star Pilot (with the diamond button), Sol! II (S), Moon Info! (M), and J-Moons! (J).
9. Dragging the stylus inside the diagram window allows you to: Identify the moon's and Saturn by name; or, ? ask for the moon's or Saturn's information.
10. Control the North/South and East/West orientation of the display to match what you see in your telescope.
11. Select a time by pressing Time:. Enter a time and press the Go button. Or step through times by pressing the - or + buttons to move backwards or forwards in time by the step value (in decimal hours).
12. Manually enter a step value (decimal hours) or select from several choices (in minutes) by pressing the Step: button. Decrement or increment the step value using the - and + buttons surrounding the step value.
13. Press the Go button anytime you manually enter a time.
14. Update the display to "now" at anytime by pressing the Now button.
15. Animate the motion of the moon's by backwards or forwards in time by using the R- and R+ selectors. Animation is accomplished by repeatedly updating the time by the amount of the step value.
16. Press these letters to identify on the display the requested moon.

Drag the stylus on the screen to display "cross-hairs". When you drag the cross-hair near to the moon or Saturn it will Identify them when the I selector is pressed.

In the Information mode (? selector selected) lifting the stylus once a moon or Saturn is identified displays additional information. Drag the stylus away from the moon or Saturn and lift up to cancel or abort displaying additional information while in this mode.

User Settable Preferences

• GMT Offset - (default for PalmOS 3.x) manually set an offset from GMT (i.e. enter your timezone here)
• Location Manager - use the Location Manager location if you have Star Pilot's Location Manager installed
• PalmOS Location - (default for PalmOS 4 or higher) Use the built-in location information, which is basically the timezone, if you have PalmOS 4 or higher.
• DST - operation depends on how you get your GMT offset information
  • GMT Offset - Auto = Use United States DST rules, DST begins at 2am on the first Sunday in April and ends at 2am on the first Sunday in October. On = Force DST. Off = No DST (default).
  • Location Manager - displays the setting from Location Manager, and it cannot be changed here.
  • PalmOS Location - displays the setting from the PalmOS location preferences panel and it cannot be changed here.
• Small Moons - show the moons of Saturn as a single pixel (picture element) instead of larger blocks (which exaggerates the scale). Default is unchecked.
• Night Mode - All the screens of Saturn! are set to red to help preserve night vision when using Saturn! with a telescope at night.
• Use High Res - (Currently Not Implemented) enables high resolution display.
• Auto Recalc - This feature is for slower handhelds. Whenever you change magnification on the main screen, the positions of the rings and satellites are recomputed. When unchecked, position calculations are only done when the date or time changes. Default is checked.
• Show JD - when checked the Julian Day number is displayed under the date on the main screen. Default is unchecked.
• Show Rings - Displaying the rings can obscure moons when the ring plane inclination is close to 0 degrees. Turn the rings off to see where the moons are in relation to the planet. Also, this helps on slower devices since drawing the rings takes time. Default is checked.
• Distance - Display distances in AU = Astronomical Units (default), Km = Kilometers, NMi = Nautical Miles, or Mi = miles.
• Vis.Mag - Compute Saturn's magnitude using the Muller's Method prior to 1984, or from the method in the American Astronomical Almanac from 1984 (default).

View Menu

• Earth Information - Show detailed calculations for Earth's position.
• Satellite Angles - Show Calculations of angles related to Saturn's moons.
• Satellite X&Y - Show the apparent X and Y coordinates of Saturn's moons in equatorial radii of Saturn.
• Saturn Information - Show detailed calculations of Saturn's position.
• Summary Report - Show interesting details of Earth, Saturn and the Sun in a summary view.
• Sun Information - Show detailed calculations of the Sun's position.

Earth Information

Information for Earth's position is required to calculate light travel time to Saturn and the apparent view of the moons.

• t = Julian millennia from epoch J2000.0
• L = the ecliptical longitude
• B = the ecliptical latitude
• R = the radius vector (which is the distance the Earth is from the Sun; for this example the value is in Astronomical Units)

For detailed explanations and examples of these values, consult Astronomical Algorithms, 2nd Edition, by Jean Meeus. Chapter 32, page 217 through page 221.

Satellite Angles, Page 1

The lambda and gamma angle calculations related to the position of Saturn's moons are displayed on this page.

For detailed explanations and examples of these values, consult Astronomical Algorithms, 2nd Edition, by Jean Meeus. Chapter 46, page 323 through page 335.

Satellite Angles, Page 2

The oemga angle and radius vector calculations related to the position of Saturn's moons are displayed on this page.

For detailed explanations and examples of these values, consult Astronomical Algorithms, 2nd Edition, by Jean Meeus. Chapter 46, page 323 through page 335.

Satellite X&Y

The apparent X and Y coordinates of Saturn's moons in equatorial radii.

For detailed explanations and examples of these values, consult Astronomical Algorithms, 2nd Edition, by Jean Meeus. Chapter 46, page 323 through page 335.

Saturn Information

Saturn's position information has to be calculated.

• Jd = julian day
• L = heliocentric longitude
• B = heliocentric latitude
• R = radius vector (= distance from Sun)
• d = distance from Earth
• T = Light Time difference from Earth
• l0 = Geocentric longitude
• b0 = Geocentric latitude
• l1 = l0 coverted to equinox 1950
• b1 = b0 converted to equinox 1950
• iPr = inclination of the plane of the ring
• P = the geocentric position angle of the northern semiminor axis of the apparent ellipse of the ring, measured from the North towards the East

For detailed explanations and examples of these values, consult Astronomical Algorithms, 2nd Edition, by Jean Meeus. Chapter 32, page 217 through page 221.

Sun Information, Page 1

Various information for the Sun's position has to be calculated to display Saturn's moons.

• T = Julian Centuries since epoch J2000.0
• L0 = Geometric mean longitude
• M = mean anomaly
• e = eccentricity of Earth's orbit
• C = equation of center
• G = geometric longitude
• R = radius vector (= distance from Earth)
• O = nutation and aberration correction
• alo = apparent longitude
• Beta = apparent latitude
• E0 = mean obliquity to the ecliptic
• E = true obliquity to the ecliptic
• ara = apparent right ascension
• ad = apparent declination

For detailed explanations and examples of these values, consult Astronomical Algorithms, 2nd Edition, by Jean Meeus. Chapter 25, page 163 through page 169.

Sun Information, Page 2

Various information for the Sun's position has to be calculated to display Saturn's moons.

• ra = right ascension
• d = declination
• nut = nutation in longitude in decimal degree seconds
• eot = Equation of Time

For detailed explanations and examples of these values, consult Astronomical Algorithms, 2nd Edition, by Jean Meeus. Chapter 25, page 163 through page 169 and Chapter 28, page 183 through page 187.

Summary Report

This summary report is created by combining information from the other information screens available in Saturn!

Actual User Photographs of Saturn

This photograph (on the right) of Saturn and five (5) of its moons and its inverted color version (which shows the moons more clearly) were taken by A. Cooper on February 15, 2004 at 18:57 MST (GMT -7.0) from Tucson, Arizona and are reproduced here by permission.

Saturn! matches up well with these photographs (considering the low resolution display of the device 160x160).