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The orrery is a simple open-source application for [[Open development/Maemo roadmap/Fremantle|Maemo 5]] which displays the night (and day!) sky. It is nowhere near as elaborate as, for example, kstars, xephem or stellarium. It is intended to be a small, finger-friendly application, requiring no network connection. The current stable version is 3.8.x (the x just increments when bugs are fixed). The program version is shown on the "Symbol Key" page.
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The orrery is a simple open-source application for [[Open development/Maemo roadmap/Fremantle|Maemo 5]] which displays the night (and day!) sky. It is nowhere near as elaborate as, for example, kstars, xephem or stellarium. It is intended to be a small, finger-friendly application, requiring no network connection. The current stable version is 3.5.x (the x just increments when bugs are fixed). The program version is shown on the "Symbol Key" page.
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The source code is hosted on [https://github.com/kenyoung/orrery this github repository]. The version there may not have gone through the Maemo Community QA testing. The most recent version which has been vetted by the community is available in the Maemo [[Extras]] catalog.  This wiki page describes the behavior of the version of the program available in the Extras Devel catalog.
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The most recent version of the program may be downloaded
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At this time, that version is also in the Extras catalog.
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[https://garage.maemo.org/projects/orrery/ from the garage project page]. The version there may not have gone through the Maemo Community QA testing. The most recent version which has been vetted by the community is available in the Maemo [[Extras]] catalog.  This wiki page describes the behavior of the version of the program available in the Extras Testing catalog.
The star database was extracted from the [[:wikipedia:Hipparcos_catalog|Hipparcos catalog]]. To ease the computational load, the coordinates are not [[:wikipedia:Precession_(astronomy)#Astronomy|precessed]] or [[:wikipedia:Nutation#Of_the_Earth|nutated]] before being displayed. [[:wikipedia:Orbital_elements|Orbital elements]] are used, rather than [[:wikipedia:Ephemerides|ephemerides]], to calculate planet positions. Although this is less accurate, it dramatically reduces the memory footprint. The planet positions are accurate to a few arc minutes, from 3000 BC to 3000 AD. Since the scale on the default display is approximately 8 arc minutes per pixel, these small errors are imperceptible, unless a very large zoom factor is used.
The star database was extracted from the [[:wikipedia:Hipparcos_catalog|Hipparcos catalog]]. To ease the computational load, the coordinates are not [[:wikipedia:Precession_(astronomy)#Astronomy|precessed]] or [[:wikipedia:Nutation#Of_the_Earth|nutated]] before being displayed. [[:wikipedia:Orbital_elements|Orbital elements]] are used, rather than [[:wikipedia:Ephemerides|ephemerides]], to calculate planet positions. Although this is less accurate, it dramatically reduces the memory footprint. The planet positions are accurate to a few arc minutes, from 3000 BC to 3000 AD. Since the scale on the default display is approximately 8 arc minutes per pixel, these small errors are imperceptible, unless a very large zoom factor is used.
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[[Image:orreryMonthlyMoonCalendar_3.2.png|thumb|200px|alt=Screenshot of monthly moon calendar|Monthly Moon Calendar]]
[[Image:orreryMonthlyMoonCalendar_3.2.png|thumb|200px|alt=Screenshot of monthly moon calendar|Monthly Moon Calendar]]
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The ''This Month's Moons'' page shows the phase of the moon for each day of a particular month. By default, the current month is shown, but one may use the arrow buttons to pan through the months.  The day of the calendar month is shown in blue in the upper left corner of each day, and the number of days since the last New Moon (the "age" of the moon) is shown in red at the bottom right corner.  The current day is highlighted with a white box with the day of the month in white and the age of the moon in pink.
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The ''This Mobth's Moons'' page shows the phase of the moon for each day of a particular month. By default, the current month is shown, but one may use the arrow buttons to pan through the months.
Both moon calendars show "[[:wikipedia:Blue_Moon|Blue Moons]]", which are (according to the most commonly used definition) the second full moon in a calendar month which has two full moons. Both images at right show the Blue Moon which falls on New Year's Eve, 2009.
Both moon calendars show "[[:wikipedia:Blue_Moon|Blue Moons]]", which are (according to the most commonly used definition) the second full moon in a calendar month which has two full moons. Both images at right show the Blue Moon which falls on New Year's Eve, 2009.
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its four main moons, which are color coded for easy identification, in their proper positions for the current time (or any other time you set).  All four moons will not always be visible - sometimes they pass behind Jupiter and are
its four main moons, which are color coded for easy identification, in their proper positions for the current time (or any other time you set).  All four moons will not always be visible - sometimes they pass behind Jupiter and are
blocked from our line of sight.  Occasionally the shadow of one of the moons will pass across Jupiter's disk, and that shadow too will be shown in the plot.
blocked from our line of sight.  Occasionally the shadow of one of the moons will pass across Jupiter's disk, and that shadow too will be shown in the plot.
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Because the inclination of Jupiter's axis is only 3 degrees, and the moons orbit nearly in Jupiter's equatorial plane, these moons appear to move nearly on a line, with Jupiter in the center.  Eclipses for the three innermost moons happen very frequently, and Callisto, the outermost Galilean Moon, is eclipsed less frequently.  Which side the moons appear on depends upon what equipment you use to observe them.  Many telescopes invert or mirror reflect the image.
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Because the inclination of Jupiter's axis is only 3 degrees, and the moons orbit nearly in Jupiter's equatorial plane, these moons appear to move nearly on a line, with Jupiter in the center.  Eclipses for the three innermost moons happen very frequently, and Callisto, the outermost Galilean Moon, is eclipsed less frequently.  Which side the moons appear on depends upon what equipment you use to observe them.  Many telescopes invert of mirror reflect the image.
There are four buttons near the bottom of the page which allow you to
There are four buttons near the bottom of the page which allow you to
invert and reflect the plots, to make them match what you see with your equipment.
invert and reflect the plots, to make them match what you see with your equipment.
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The Events page lists the times of the satellite events such as eclipses, occultations and transits.  This page takes a second or so to plot,
The Events page lists the times of the satellite events such as eclipses, occultations and transits.  This page takes a second or so to plot,
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because it requires roughly one million double precision trigonometric functions to be evaluated (the event timings are calculated by your phone, not fetched from a website). Since the app is location-aware, it can tell you which of these events will be visible to you from your current location.    If the Sun is above the horizon, or Jupiter is below the horizon, you cannot see a satellite event; such events are listed in grey.  Events that you can see are shown in green, except for he ''next'' event you can see, which is shown in red.  The times are all in UT, of course.  The plot on the right shows the events for the very special evening of Oct 12, 2013.  On that night three satellite shadows crossing Jupiter's disk are visible at once (see plot at the top of the page).  The color coding shows that this rare triple shadow event will be visible from my current location.
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because it requires roughly one million double precision trigonometric functions to be evaluated. Since the app is location-aware, it can tell you which of these events will be visible to you from your current location.    If the sun is above the horizon, or Jupiter is below the horizon, you cannot see these events, so they are listed in grey.  Events that you can see are shown in green, except for he ''next'' event you can see, which is shown in red.  The times are all in UT, of course.  The plot on the right shows the events for the very special evening of Oct 12, 2013.  On that night three satellite shadows are visible at once (see plot at the top of the page.  The color coding shows that this rare tripple shadow event will be visible from my current location.
At the bottom of the Events page is a button you can click to return to the Graph page.
At the bottom of the Events page is a button you can click to return to the Graph page.
{{clear}}
{{clear}}
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==== Celestial Navigation ====
 
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[[Image:orrerySextantFullList.png|thumb|200px|alt=Screenshot of the Celestial Navigation Default Page|Celestial Navigation Default Page]]
 
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The Celestial Navigation page shows the information needed to perform [[wikipedia:Celestial_navigation|celestial navigation]] calculations with a [[wikipedia:Sextant|sextant]].  The default page, shown on the right,  shows the information presented by the [[wikipedia:US_Naval_Observatory|US Naval Observatory]] on its online calculator (located at http://aa.usno.navy.mil/data/docs/celnavtable.php).
 
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The orrery does not use that Naval Observatory calculator; it calculates the values itself (so you do not need an internet connection to use it).  The orrery uses the same list of objects as the Naval Observatory calculator, but it color-codes them differently for improved visibility.  Solar System objects are shown at the top of the list in red.  Objects with elevations between 15 and 65 degrees are shown in green, and objects above the horizon but outside of that range are shown in grey.  Data for Polaris and the First Point in Aries are shown at the bottom of the table, in white.  The values are not updated as time passes unless you press the "Press Here to Update" button at the bottom of the page.
 
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If you need the reduction table values for some arbitrary time, you can of course use the normal method of changing the orrery's time, and then return to the Sextant Navigation page to see the appropriate values.
 
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[[Image:orrerySextantSingleObject.png|thumb|200px|alt=Screenshot of the Celestial Navigation Single Object Page|Celestial Navigation Single Object Page]]
 
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Showing all of the navigational objects on one page requires a very small font, which is hard to read.  If you press the touchscreen near any of the objects, a white box will appear highlighting a selected object.  Releasing the screen will present another page showing the data for the selected object only, with a much larger, more readable font, as shown on the right.
 
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{{clear}}
 
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==== Lunar Eclipses ====
 
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The orrery can display information about every [[:wikipedia:Lunar_Eclipse|lunar eclipse]] occurring from from 1999 BC through 3000 AD - a bit more than 12000 eclipses (the database used is the "Five Millennium Canon of Lunar Eclipses: -1999 to +3000" available at http://eclipse.gsfc.nasa.gov/SEpubs/5MCLE.html, although the orrery generates its own maps).  It will display information about the visibility and duration of the eclipse as seen from the current location.  When one selects the Lunar Eclipse page, the checklist page shown on the right is presented.[[Image:OrreryLunarEclipsePage1.png|thumb|200px|alt=Selection page for Lunar Eclipses|Selection page for Lunar Eclipses]] Because so many eclipses can be displayed, by default the user is presented with a small subset of the eclipses: those which occur during the next 10 years.  One may change the starting and ending years to access other eclipses.  The "List only eclipses visible from here" checkbox allows you to produce a list of only those eclipses for which at least some portion of the eclipse is visible at your location.  Other checkboxes allow you to decide which types of lunar eclipses; penumbral, partial and/or total, you wish to display.  By default [[:wikipedia:Lunar_Eclipse#Types_of_lunar_eclipse|penumbral]] eclipses are not displayed, because they involve only a rather subtle changing of the moon's illumination.    If you change any of the selection criteria on this page, you need to tell the program to generate a new list of eclipses to display by pressing the "Rebuild the Eclipse List" button.  If you don't change the checkboxes, you do not need to push that button.  '''To select the eclipse you wish to observe, click the "Click Here to Select the Eclipse to Display" area''', and you will be presented with a scrollable list of eclipses to choose from.  You will not be presented with an eclipse list unless you click in that region (shown outlined in red, in the screenshot to the right).
 
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Once you have chosen the eclipse you're interested in, you will be shown information about that eclipse on a new page.  Once such image, for the total lunar eclipse of April 15, 2014,  is shown on the right.[[Image:OrreryLunarEclipsePage2.png|thumb|200px|alt=Lunar Eclipse Display Page|Lunar Eclipse Display Page]]  Below the title of the page, the orrery displays whether or not you can see the selected eclipse.  If the moon rises or sets during the eclipse, that information is listed too.  Below that, the duration of each phase of the eclipse (as seen from your location) is listed.  Below that, the starting and ending times of each phase, along with the time of maximum eclipse, is listed.  All times are in Universal Time.  Remember that if you observe the penumbral phase of the eclipse, the changes in the moon's appearance may not even be noticeable; only the partial and total phases are visually striking.
 
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The upper graphic on the eclipse display page shows the path of the moon through the earth's shadow.  The [[:wikipedia:Umbra|penumbra]] (where the earth only partially blocks the sun as seen from the moon) is shown in light grey and the umbra (where the earth completely blocks the sun as seen from the moon) is shown in darker grey.  The ecliptic is shown in red, and the path of the moon is indicated with a turquoise arrow.  If the moon rises or sets at your location during the eclipse, the moon's position in the shadow at that time is shown in red.
 
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At the bottom of the eclipse display page a map is presented showing the portions of the earth which can see the eclipse.  The observer's location is indicated with a red dot, and the map itself is centered at the longitude of the observer.  The light blue dot shows the position on the earth for which the moon is at the zenith at the moment of maximum eclipse.  The light blue line shows the longitude for which the moon is on the [[:wikipedia:Meridian_(astronomy)|meridian]] at the moment of maximum eclipse.  The darkest grey region shows the portion of the earth for which none of the eclipse can be seen.  Observers in the white region can see at least some portion of the maximum phase of the eclipse.  In other words, if the eclipse is total, an observer in the white region sees at least some part of the total phase of the eclipse.  If the eclipse is partial, an observer in the white region sees a partial eclipse.  Other shades of grey are used for regions that, for example, can only see the partial phases of a total eclipse.  The next image to the right indicates the meaning of the various shaded regions and lines on this eclipse visibility plot.[[Image:OrreryLunarEclipseMapKey.png|thumb|200px|alt=Lunar Eclipse Visibility Plot|Lunar Eclipse Visibility Plot]]
 
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{{clear}}
 
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{{clear}}
 
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==== Comets ====
 
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The Comets page displays information about any [[:wikipedia:Comet|comet(s)]] that the app knows about.  An example of the display produced is shown on the right.[[Image:orreryCometPage.png|thumb|200px|alt=Comets Page|Comets page]] Information for comets which are currently below the horizon is shown in grey (as is the case for comet [[:wikipedia:C/2011_L4|Pan-STARRS]] in the sample page).
 
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Unlike the major planets, comet information for orrery is obtained from
 
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[[:wikipedia:Ephemerides|ephemerides]] obtained from the [[:wikipedia:JPL_Horizons|JPL Horizons website]].  Ephemerides are used for comets because their orbits may be strongly perturbed by the major planets as the comets move through the inner Solar System.  Since ephemerides are used, the orrery can only display information for a comet during the period covered by the ephemeris, usually one year before and after the periheion passage.  Outside of that period the comet is ignored and not plotted anywhere.
 
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In addition to the Comets page, comet information shows up several other places.  The comet will be plotted on the sky map page (default page) if showing comets has been enabled via the Displayed Items menu page.  Comets will also be shown on the Planet Compas page, the Planet Elevations page and the To-scale Solar System page.  Note that if their are comets visible, there will be a button in the upper left area of the Planet Elevation page allowing you to toggle between showing planets and showing comets.
 
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The To-scale Solar System page shows the orbits projected onto the Solar System's equatorial plane.  Since comets follow paths that are often very highly inclined to that plane (as is the case for comet Pan-STARRS), this projection effect can make it look like the Sun is not at the focus of the orbit, but of course it must be.  This is merely an illusion.
 
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===== Adding Additional Comets =====
 
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You can add more comets for the orrery to display.  To do so, you need to create an ephemeris file.  The file must have the following format:
 
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The first line must contain the name of the comet, optionally followed by a second "nickname" for the comet.
 
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All other lines must be formatted as follows:
 
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Character Range                        Description
 
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  0 ->  3                          Year (2012, etc)
 
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  5 ->  7                          Month (Jan, Feb, etc)
 
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  9 -> 10                          Day of month
 
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12 -> 13                          Hour
 
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15 -> 16                          Minute
 
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18 -> 28                          Geocentric RA (HH:MM:SS.SS)
 
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30 -> 40                          Geocentric Dec (+DD:MM:SS.SS)
 
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43 -> 47                          Magnitude (MM.MM)
 
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49 -> 56                          Ecliptic Longitude (DDD.DDDD)
 
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58 -> 65                          Ecliptic Latitude (+DD.DDDD)
 
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67 -> 79                          Distance from Sun (AU)
 
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This information can be easily obtained from the JPL Horizons website.  For the ephemerides I include with the package, I have one entry for every time the comet moves by one degree in the sky, so the sampling is much finer near perihelion.  The file must be placed in the directory /opt/maemo/usr/share/orrery/comets/ .  The name of the file does not matter.
 
=== Displayed Items ===
=== Displayed Items ===
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== Chinese Color Scheme ==
== Chinese Color Scheme ==
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In traditional Chinese astronomy, the zodiac is known as the Yellow Way, and the celestial equator is known as the Red Way. If you want the orrery to use that color scheme for great circles and constellations, edit the file <code>/usr/share/orrery/config</code>, and make the first line read
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In traditional Chinese astronomy, the zodiac is known as the Yellow Way, and the celestial equator is known as the Red Way. If you want the orrery to use that color scheme for great circles and constellations, edit the file <code>/usr/share/orrery/config</code>, and make the first lineread
  CHINESE_COLOR_SCHEME 1
  CHINESE_COLOR_SCHEME 1

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