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The Photographer's
Ephemeris™
Welcome to TPE! This app helps you understand how natural light interacts with locations
across the globe. It is designed primarily for photographers who want to include the sun or
moon in their photographs, or to understand how natural light will strike their chosen subject.
Please read through these pages to get the most out of the tool.
Basic information, such as the time and direction of sunrise, is easily found in the app, but there
are a significant number of advanced features that you'll probably want to read about in more
detail.
Overview
The Photographer's Ephemeris (TPE) provides tools to help with the planning of natural light
photography, particularly landscapes and cityscapes.
Basics
Here's the 60-second version to help you get started quickly:
Use the Map, timeline and altitude chart to visualise and understand the movement of the
sun and moon through the day.
Tap the date to choose between day and night modes and to set the current date, or
choose from a list of celestial events, or use the date navigation buttons to move
back/forward day-by-day or event-by-event
The Geodetics function (enabled using the grey map pin button) shows you distance,
bearing and line of sight between any two points
You can search for Locations by name and save any you want to return to. Add notes to a
saved location for future reference or manually enter latitude/longitude.
Use Visual Search to find when the sun or moon will appear at a specific point. Set the
azimuth (direction) and altitude (height above the horizon) using the grey pin on the map
Shadow length for an object of a certain height (e.g. a building) can be calculated. You can
also set object heights for the grey pin, and enter offsets to the given elevation data
The Horizon tool calculates distance to the visible horizon and adjust rise/set
times/directions if you elevated above the ground
Use Settings to select your preferred map technology, units, magnetic north and more
Date and Mode Controls
The selected date and mode is displayed at the top of the screen, along with additional
controls to change the date. The sun and moon data displayed on the map below is always
calculated for the selected date, so it's important to ensure this is set correctly.
The app can be used in two distinct modes, day mode and night mode. The current mode
is indicated by the icon to the left of the date at the top of the screen:
The app shows sun and moon data for period from midnight-toDay Mode
midnight for the selected date. Use this mode for daylight
photography, including sunrise. sunset and twilight.
The app shows moon, milky way and star data for the period
Night Mode
midday-to-midday, starting at midday on the selected date. Use this
mode for night photography.
You can control the selected date using dedicated buttons as follows:
Previous
Set date/time to that of the previous celestial event before the
Event
current selected date
Previous
Day
Next Day
Next Event
Move back one day
Move forward one day
Set date/time to that of the next celestial event after the current
selected date
Note
Previous/next event buttons are not shown on devices with 3.5 or 4 inch screens (e.g.
iPhone 4/4S, iPhone 5). You can select events from the list displayed by tapping the
selected date
Mode
Select either day or night mode using the options shown.
Select date
Tap the date displayed at the centre of the navigation bar to select a particular date. A date
picker control and list of celestial events is displayed. Tap Now to select the current date and
time. Note, that the time is set to that of your device's internal clock, irrespective of the time
zone for the current location shown on the map.
Celestial Events
Dates of key celestial events for the selected year are shown. The list is filtered to exclude any
events earlier than eight days prior to the selected date. If you would like to see earlier events,
simply change the selected date. If you would like to see events for a different calendar year,
change the selected year. An icon next to each event type indicates whether, qualitatively
speaking, it is a 'major' or 'minor' event:
Full moon
New moon
Lunar Perigee
Equinox
Solstice
Lunar + Solar Eclipses
Major meteor showers
First quarter
Last quarter
Moon at apogee
Perigee is the moment at which the moon reaches its closest approach to earth during the
monthly lunar cycle, appearing largest in the sky. When perigee coincides with a full moon, a
perigee moon (also known as a ‘supermoon’) can be observed.
Apogee is the moment at which the moon reaches its greatest distance from earth during the
monthly lunar cycle, appearing smallest in the sky.
Equinox occurs twice a year, during spring and autumn, when the sun lies directly over the
equator. Sunrise and sunset occur more or less due east at these times.
Solstice also occurs twice a year, during mid-summer and mid-winter, when the sun rises or
sets at its maximum and minimum azimuth.
Where a lunar event indicates x% larger, this represents the observed size of the moon's disc
relative to its size when the moon is at extreme apogee (farthest from Earth).
Some events, including eclipses and meteor showers, have additional information available. Tap
the event to view its details. Tap Select or the date row to set the app to the date of the
event. For events that span a period of time, the 'peak' or 'maximum' date is set (for example,
the time of greatest eclipse, or the night of peak activity for a meteor shower).
The Map
TPE shows the direction of the sun and moon overlaid on a map. Lines are drawn from the
primary pin outward showing the direction of various events, depending on the selected
mode.
In Day mode:
Sun/moon rise/set are shown for the selected date, and sun/moon position for the selected
time of day. (See below for additional information on shadows display.)
Sunrise
Sunset
Moonrise
Moonset
Sun position
Moon
position
In Night mode:
Rise and set are shown for both moon and the galactic centre (the centre of the Milky Way)
on the selected date. The current position of the moon and galactic centre are displayed, along
with some specific additional alignment lines (described in more detail below):
Moonrise
Moonset
Galactic
Centre rise
Galactic
Centre set
Moon
position
Galactic
Centre
position
Alignment lines are drawn in Night Mode to depict the following items:
Azimuth +
altitude of
As noted above, this line points from the red pin location to the centre
Galactic
of the Milky Way.
Centre
Milky WayHorizon
alignment
Azimuth +
altitude of
the pole star
A line is drawn through the red pin connecting the points in the band of
the Milky Way where they cross the horizon. If you want to capture a
shot of the Milky Way rising into the sky from a point on the horizon,
this line shows the required shooting direction.
A line is drawn through the red pin connecting the Galactic north and
south poles, which lie in close proximity to Polaris and Polaris Australis
respectively. Use this line to determine required shooting direction for
star trail photographs.
Milky Way
A symbolic representation of the Milky way is shown in Night Mode. The central band of the
Milky Way is shown as a ring of spheres, which increase in size and brightness towards the
galactic centre.
The Milky Way is a spiral galaxy, that is array as a flat disk with a central bulge. Earth lies near
the central plane of the Milky Way, but away from the centre. As a result, the Milky Way is
observed as a band in the sky with brighter region towards the galactic centre.
Note
In far northern latitudes, the Galactic Centre is never visible due to the orientation of
Earth relative to the Milky Way. At moderate or lower northern latitudes, the Galactic
Centre is visible only during summer.
Major Stars and Constellations
In addition the the symbolic Milky Way representation, major stars and constellations are
shown in their correct relative positions in the night sky.
The following constellations are shown: Canis Major, Orion, Ursa Major, Crux, Aquila, Aries,
Cassiopeia, Cygnus, Gemini, Leo, Lyra, Scorpius, Taurus, and Ursa Minor.
Additionally, the very brightest stars from the following constellations are shown: Carina,
Centauri, Bootes, Auriga, Canis Minor, Eridanus, Virgo, Piscis Austrinis, Sagittarius, Canes
Venatici, Pegasus, Andromeda.
Tip
As drawn on the map, the constellations are viewed from "outside-in". Imagine you're
on the outside of a transparent planetarium, looking in. Well-known constellations and
star patterns such as Orion, Crux (Southern Cross), and the Plough (Big Dipper),
should be easily recognisable.
Tap a star to see its common name, Bayer designation and current azimuth and apparent
alititude (calculated for the current date/time, latitude and longitude). When you tap the star it
momentarily increases in size for ease of identification. The color of the star can be observed:
the color is derived from the star's B-V index. For example, Betelgeuse, a red giant, appears
with a disinctly yellow-reddish hue.
Bayer Designation
The Bayer designation for a star is formed of a greek letter (α, β, γ, where α is the
brightest star in the constellation), followed by the constellation name (in the Latin
genitive form), e.g. Sirius is known as α Canis Majoris, the brightest star in Canis Major.
Asterisms
Asterisms are easily recognized patterns of stars used by astronomers to locate particular
regions and objects in the sky. An asterism may be made up of a subset of stars in a
constellation (such as the Plough or Big Digger), or may be formed of stars from multiple
constellations (such as the Great Square of Pegasus, which includes the star Alpheratz from
the constellation Andromeda).
The following asterisms are displayed in Night Mode:
Summer Triangle
Teapot
Big Dipper or Plough
Little Dipper
Great Diamond
Great Square Of Pegasus
Winter Triangle or Great Southern Triangle
Winter Hexagon
Tip
If you want to locate the Galactic Centre in the sky during twilight when it's still too
light to see the Milky Way clearly (e.g. to set up for a shot in advance), the Teapot of
Sagittarius is a useful pointer: the band of the Milky Way appears as 'steam' emerging
from the spout of the teapot, with the Galactic Centre located close to the tip of the
spout.
You can check the alignment of the teapot to the Milky Way using the asterism
visualization in TPE.
Interacting with the Map
The map supports a number of different gestures:
Pan
Tap and drag on the map to pan in any direction
Double tap
to zoom
Tap twice on the map to zoom in
Pinch to
Pinch the map with two fingers to zoom in, or move them apart to
zoom
zoom out
Rotate
Touch the map with two fingers and twist to rotate the map
Touch the map with two fingers, aligned horizontally across the map, and
push up to tilt the map away. Pull down to tilt the map back to the
Tilt
normal top down view. Note: for Apple maps, tilt is only available with
the standard map type, and only at higher zoom levels.
Map Controls
Map Pins
The map always displays a red primary pin marking the location for which rise/set
calculations are performed.
Optionally (see below), the map can also display a grey secondary map pin. This
map pin is for use with the geodetics functionality.
The map pins can be moved by touching and then dragging. If using Apple maps, you must
touch the pin once to select it before it can be moved. Touch and hold the map pin until it
animates up, then move your finger to reposition where required. Avoid moving the pin too
quickly.
When the map is moved, such as by panning or zooming, a reticle appears to indicate the
centre of the map. The reticle is hidden a couple of seconds after the map move finishes.
Tapping the reticle while it remains visible will place the primary pin (see below) at the map
centre.
In many situations, the primary pin can be thought of as your shooting location, i.e. where the
camera is situated. This is particularly true if you plan to include the sun or moon in your shot.
However, if you plan to photograph a building or landscape illuminated by the sun or moon,
then red pin should be placed on your subject. In this case, you can set the secondary pin at
your shooting location to determine line of sight, distance and bearing.
The following controls appear at the top right of the map:
Track location and heading
Track
location off
Other than when first using the app (see below), location
tracking is off by default. When enabled, the map will
automatically be centred on the current device location.
On first using the app, if you grant permission to use your
Track
current location, the app will automatically attempt to centre the
location on
map on your device's current location, if known. You can enable
location tracking by pressing this button.
On devices equipped with a compass, if location tracking is
Track
heading on
already enabled, a further press of this button will enable heading
tracking. When enabled, the map is automatically rotated such
that it points to true north. Press again to disable both location
and heading tracking.
Note
When using Track heading, the built-in compass in your device is significantly less
accurate than the bearings and azimuths calculated by TPE. We recommend using a
high quality field compass to determine your bearing if your shot depends on high
precision.
If you reply on the internal compass, it is critical to ensure the device is clear of any
other objects. Even if not requested to do so by an on screen prompt, we recommend
moving the device in a figure-of-eight motion for 10-20 seconds to maximize the
chances of an accurate compass measurement.
Map controls
Recentre
Press this button to reposition the red (primary) map pin to the
primary pin
centre of the map.
Press to enable geodetics. When enabled, a grey secondary
map pin is displayed by default due east of the map centre. This
can be used to measure distance and elevation changes between
the primary and secondary points and to analyse line-of-sight.
Geodetics
See below for more information.
If already enabled, you can reset the grey pin to its default
position due of the map centre using a long press on this
button.
Map
Tap to manage available map overlays. See below for more
overlays
information.
Selected
map type
Tap to change the current map type selection.
Geodetics controls
To disable geodetics, press the 'back' button:
Recentre
Press this button to reposition the red (primary) map pin to the
primary pin
centre of the map.
Reset
secondary
pin
Tap to reset the secondary pin to a default position due east of
the map centre.
Swap map
When geodetics is enabled, this button can be used to swap the
pins
red and grey map pin positions.
Zoom to fit
Tap to zoom the map so that both priamry and secondary map
pins are shown.
Map overlays
To exit map overlay selection, press the 'back' button:
Back
Return to default map controls
Press to enable or disable Skyfire overlays. Skyfire overlays are
shown around sunrise and sunset: you may need to adjust the
selected date and time of day and also zoom out to view this
Skyfire
map overlay.
Skyfire requires a susbcription. This button may not be shown if
your device is configured for a region outside the Skyfire
coverage area.
Press to enable/disable light pollution overlay. Light pollution is
Light
shown during the hours of darkness only: you may need to
pollution
adjust the selected time of day and also zoom out significantly
to view this map overlay.
Stars
Press to enable/disable display of stars and asterisms in Night
Mode.
Map type selection
A number of different map types are available within the app. The best choice will depend on
your situation - see notes of each choice below. The available choices depend on which map
technology (Google or Apple) you have selected in the apps Settings.
Standard
Satellite
Hybrid
Standard map, particularly suitable for cities and towns.
Satellite map with overlaid street, road and placename data.
Suitable for locations where you need to see details of objects
on the ground.
Terrain
Default Topographic map, especially suited for landscape
Google only
photography.
Open Street
Map
Google only
Open Cycle
Available offline Alternative standard map type using OSM data.
Any areas you view within the app will (subject to available
storage on your device), remain available to view while offline for
up to 1 year after viewing.
Available offline Alternative topographic map type. Any areas you
view within the app will (subject to available storage on your
Map
device), remain available to view while offline for up to 1 year
Google only
after viewing.
Hiding the map controls
The map control buttons can optionally be hidden to create additional working space for
viewing the map.
Hide
controls
Show
controls
Hide the map control buttons.
Show the map control buttons.
Map Information
Status indicators are shown at the top left corner of the map and have the following meanings:
Unknown
Timezone
and
elevation
unknown
Timezone and elevation status unknown. This can be shown while
the app initializes before it has made any data requests.
Timezone and elevation data not received. This status is shown
while the app is waiting for data to be received, or if your device is
offline.
Timezone
OK,
elevation
Timezone received, waiting for elevation.
unknown
OK
Timezone and elevation OK
If timezone is unknown, the last known timezone (or any override timezone you set) is used
for the sun/moon calculations. The current timezone the app is using is displayed at the top
left of the map next to the status indicator.
Important
If the status indicator does not display as OK, double check the timezone shown and
ensure it is appropriate for your selected location.
Elevation above sea level and the coordinates of the primary pin location are shown at the
top right of the map. If elevation is unknown, a question mark (?) is displayed, and sea level is
assumed for all calculations. Incorrect elevation can result in small differences in calculated
rise/set times and directions.
Timeline
A timeline of daily events is shown beneath the map. Events are arranged in chronological
order from left to right through the day. In Day mode, these include twilight times, sunrise,
sunset, moonrise, moonset, moon phase and crescent moon visibility.
In night mode, instead of the sun, the Galactic Centre is displayed.
Each data panel in the timeline may include the following information:
Colour key: if the event corresponds to an azimuth line drawn on the map, the line colour
is shown
Event name: the name of the event, e.g. sunrise, optionally with an accompanying icon.
Time: the time at which the event occurs
Azimuth: the azimuth in degrees at which the body (e.g. sun or moon) will appear. (This is
either true north or magnetic north depending on your chosen settings
Additional information: depending on the event type, additional information is
displayed here. For example, for the moon, the phase and percentage illumination is shown
Note: if elevation above the horizon is set (see below) Event name captions for rise/set events
are displayed in italics to indicate that the altitude of the body (e.g. sun or moon) for which rise
or set is calculated has been adjusted for the dip of the horizon.
The following gestures can be used to control the timeline:
Swipe left/right to scroll the timeline content
Swipe down to hide the timeline (swipe up on the altitude chart to redisplay the timeline)
Tap on a particular event to set the selected time of day to that of the specific event
Double Tap or Long Press to configure the timeline display
Sightline checks
Sunrise and sunset (any 'rise' or 'set' event, in fact) is always measured relative to the
unobstructed horizon.
Important
If there's a hill or ridge in the way, you won't be able see the moment of sunrise or
moonrise.
To help clarify when rise or set events are obstructed, TPE will automatically check the
sightline upon tapping an event in the timeline. The app samples elevation along the azimuth of
the event for a distance of 100 miles and checks to see if the horizon is obstructed. The
sightline check can only account for variation in the terrain: it does not account for man-made
obstructions (e.g. buildings) or trees.
If an obstruction is found, the event is marked as not visible and a message is displayed
showing where the largest obstruction on the sightline was found:
Once a timeline event is selected, you can tap it again to display an options menu. Options are
shown to view the elevation/altitude profile in the direction of the event using the Geodetics
tools described below.
Note
You can use Geodetics and Visual Search to determine when the sun or moon will
appear above a ridge or mountain.
Timeline Display Options
You can configure the timeline to display different sets of information, appropriate to how you
use the app. In Day mode, options include:
Default
Includes sun and moon rise/set, civil and nautical twilight, moon phase
and crescent moon visibilty
Daylight
Essentials
Includes civil twilight and sun rise/transit/set.
iPhone only
Daylight +
Includes sun and moon rise/set, civil twilight, moon phase and crescent
Moon
moon visibilty
Extended
Daylight
Includes sun rise/set/transit, civil and nautical twilight, and 'golden hour'
In Night mode, they are:
Night
Includes moon and galactic centre rise/set, all twilight data, moon phase
Default
and crescent moon visibilty
Night
Essentials
Night All
Includes moon rise/set, nautical and astronomical twilight, moon phase
Includes moon and galactic centre rise/set and transit, all twilight data,
moon phase and crescent moon visibilty
Timeline Events
The events displayed in the timeline have the following meanings:
Sunrise
The moment at which the upper limb (top edge) of the sun appears on
an unobstructed horizon (i.e. no hills or buildings in the way)
Sunset
Moonrise
Moonset
Astro start
Astro end
The moment at which the upper limb of the sun disappears below an
unobstructed horizon
The moment at which the upper limb of the moon appears on an
unobstructed horizon
The moment at which the upper limb of the moon disappears below an
unobstructed horizon
The start of astronomical twilight, when the centre of the sun's disc
ascends above -18° altitude
The end of astronomical twilight, when the centre of the sun's disc
descends below -18° altitude
Nautical
The start of nautical twilight, when the centre of the sun's disc ascends
start
above -12° altitude
Nautical end
Civil start
Civil end
The end of nautical twilight, when the centre of the sun's disc descends
below -12° altitude
The start of civil twilight, when the centre of the sun's disc ascends
above -6° altitude. Also known as 'dawn'.
The end of civil twilight, when the centre of the sun's disc descends
below -6° altitude. Also known as 'dusk'.
There is no scientific definition of the colloquialism 'golden hour'. We
choose to define it here as the opposite of Civil twilight, i.e. when the
Golden hour
sun is lower than +6° in altitude. Generally, this period corresponds to
the best chance of good light for stills photography. (Cinematographers
and commercial photographers will often prefer to shoot during 'magic
hour' which generally corresponds to the period of civil twilight.)
Full moon
The moment of full moon (when the moon is in opposition to the Sun
and is fully illuminated).
Third
The moment of third (or last) quarter moon (when the moon is waning
quarter
and half illuminated).
The moment of new moon (when the moon is closest to the sun in the
New moon
sky). The moon is not visible to naked eye at the moment of New moon
(and generally not for 1-3 days after this, depending on timing and
location)
Indication of visibility for the new moon. Possible indications include 'Try'
Crescent
(a telescope or binoculars is likely required) or 'Best' (moon can be
moon
most easily be observed at this time, with the naked eye). The letters A
visibility
to F indicate the moon visibility classification according to the Yallop
method.
The sun transit time, also referred to as sun-meridian transit time, is the
time at which the sun passes over the observer's meridian line (i.e. 0° or
Sun transit
180°). Most often this time is used as local noon time and therefore will
differ from longitude to longitude. It corresponds approximately to the
moment when the sun is at its maximum altitude for the day. The length
of day is also displayed.
The moon transit time, also referred to as moon-meridian transit time, is
Moon
the time at which the moon passes over the observer's meridian line. It
transit
corresponds approximately to the moment when the moon is at its
maximum altitude for the day.
GC rise
GC set
The time when the galactic centre (the centre of the Milky Way) rises at
the ideal horizon.
The time when the galactic centre (the centre of the Milky Way) sets
below the ideal horizon.
The time when the galactic centre (the centre of the Milky Way) crosses
GC transit
the observer's meridian line, also referred to as galactic centre-meridian
transit time. It corresponds approximately to the moment when the
galactic centre is at its maximum altitude for the day.
All rise and set events include corrections for elevation above sea level, elevation above the
horizon (if specified), and atmospheric refraction and are believed to be accurate to within one
minute between latitudes of +70° and -70°.
Note
Sun/moon rise/set do not always occur on every date in every location. At high
latitudes, for example, the sun may remain above or below the horizon for many days.
In particular, you will frequently see days in which either moonrise or set does not
occur, due to the innate timing of the cycle of the moon.
Additionally, not all twilight phases occur in all locations/times. For example, the sun
may never set far enough for there to be an astronomical twilight phase at northern
latitudes in summer.
Moon events typically include either the percentage illumination of the moon's disc at the time
of the event, or the time since or until the previous or next moon phase event.
Altitude Chart
The altitude chart shows the altitude of the sun and moon through the day (in Day mode), or
the altitude of the moon and galactic centre (in Night mode), measured in degrees relative to
the ideal horizon. A higher value corresponds to the sun or moon appearing higher in the sky.
The chart legend shows the selected time of day, and the corresponding azimuth and altitude
of the sun and moon.
The following gestures can be used to control the altitude chart:
Swipe left/right to adjust the selected time of day
Tap once to adjust the selected time by plus or minus one minute. Tapping to the right of
the time indicator adds one minute. Tapping to the left subtracts one minute.
A Double Tap toggles the shadow display on or off (see below) unless on iPhone when
Geodetics is enabled, in which case a double tap toggles between Sun/moon altitude and
elevation or altitude profile
Swipe up to show the timeline, if it was previously hidden (swipe down on the timeline to
hide it again)
The azimuth lines on the map adjust their position to match the time of day displayed on the
chart legend
The chart shows apparent altitude (that is, altitude adjusted for the effects of atmospheric
refraction) when the sun or moon is visible above the horizon. When below the horizon, the
true altitude is displayed. You may observe a small discontinuity in the plotted data just below
the zero degree line as a result. The effect of atmospheric refraction is to appear to 'lift' the
sun or moon in the sky slightly higher than they would otherwise be observed. The magnitude
of the effect decreases with positive altitude.
The +6° Shadow Circle
While you adjust the selected time of day, a circle is displayed on the map.
By default, the diameter of the circle is calculated to more or less span the visible map area.
The circle is shown in conjunction with the sun and moon shadow lines which appear in the
opposite direction to the sun and moon azimuth lines on the map, and appear as shown:
Sun
shadow
Moon
shadow
When the length of a shadow line coincides with the edge of the circle, that indicates that the
sun or moon is at that time +6° above the horizon, corresponding (according to our
definition) to the start or end of so-called 'golden hour' (for the sun), or when the moon is
low in the sky and can more easily be photographed juxtaposed next to buildings or features
in the landscape
When the sun or moon is below +6° the shadows line will extend outside the +6° shadow
circle. If the sun is below +6°, the circle turns orange to indicate the possibility of good light.
Note: if you have entered a primary object height on the Shadows page (see below), then
the diameter of the circle is calculated to correspond to the length of shadow cast by an
object of the height you specified, rather than being calculated to fill the map span.
Geodetics
Geodetics is enabled by pressing the enable geodetics button on the map, as described above.
When enabled, the geodetics tool provides key information for the path between red and grey
map pins. You can use this information to help plan your shot.
When enabled, the distance, bearing, difference in elevation and altitude angle are shown, as
measured from primary (red) to secondary (grey) pin.
In addition, the elevation or altitude profile between the two map pins is displayed. This helps
to visualize the terrain and possible line of sight between camera and subject. Once the
elevation profile data is received, the altitude display is changed to show the maximum altitude
(in degrees) along the path.
The chart shows the following information:
The primary (red) pin corresponds to the left of the chart
The secondary (grey) pin corresponds to the right of the chart
Terrain that is visible from the primary pin position is indicated by a solid line
Terrain that is obscured as viewed from the primary pin position is indicated by a dashed
line
The sun or moon are shown on the chart if they lie within 45° of the bearing from primary
to secondary pins. The line are shown with transparency if the azimuth is greater than 2.5°
difference. If the sun or moon would be obscured, the line is shown as dashed
The chart supports the following gestures:
Tap once to toggle scale-to-fit on off.
A Double Tap to switch between elevation and altitude profile on iPad, or to cycle
between elevation, altitude and sun/moon altitude charts on iPhone
The altitude chart displays the altitude angle along the line from primary to secondary pin. In
this mode, the sun/moon altitude lines appear horizontal. The altitude chart can provide a
better representation of the relative size of objects as viewed from the primary pin. For
example, mountains that are taller, but farther away, appear in the correct relative size on the
altitude chart, but always appear taller on the elevation chart.
TPE uses elevation data from both Google Elevation Service and the Shuttle Radar
Topography Mission (SRTM30). Data points are typically spaced between 30m and 90m (295ft)
apart. If the distance between the map pins is less than the data spacing, a warning icon is
displayed indicating that there may not be sufficiently granular data available to calculate
accurate results.
Locations
Select the Locations tab (iPhone) or press the Locations button (iPad) to search for, save and
return to your favourite places.
Touch the "+" button to add a new location using the current primary pin position (or select
between primary and secondary pins if geodetics is enabled).
Alternatively, type a place name in the search field. This will do two things: (i) filter your list of
saved locations for any matching or partially matching titles; (ii) search the web for
corresponding place names using a geocoding service. Note that you will need to cancel the
search to access the "+" and synchronize buttons, as these controls are hidden by iOS while
the search is active.
Tap to select a search result. Two or three buttons are displayed:
Move the primary pin to this location
Move the secondary pin to this location, and enable geodetics if necessary
Save location to your list
Edit location: you can rename it, manually change the coordinates, or add notes
TPE saves the timezone and elevation above sea level for locations (as long as the device has
Internet connectivity) so you can obtain accurate rise/set information for saved locations
without needing network connectivity at a later time.
To delete a location, swipe left on the entry in the locations list and choose Delete.
Favorite Locations
You can mark a location as a favorite by tapping the star button in the location list.
Locaion is a favorite
By default, favorite locations are always shown the map (you can override this in Settings).
Additionally, after tapping in the search bar, you can filter your locations list to display only
favorites.
Location Synchronization
Location synchronization is available as a subscription feature within the app. On first tapping
the button, you will be prompted to sign up or sign in, if necessary. A 90-day free trial is
available, after which a subscription is required.
Synchronize locations
Once you are signed up for Location Synchronization, your saved locations can be shared
across multiple devices running TPE on iOS, and also with the TPE web app
(app.photoephemeris.com). This allows for planning at home on a desktop computer, after
which you can synch your locations to your mobile devices for use in the field.
As with the TPE web app, the latest edits to a location are retained in the case of a
synchronization conflict (i.e. the same location was edited on two different devices). Note: the
time of the edit is what is tested, not the time when you synchronize.
Once a location has been synched, and if you are signed into your account, a cloud icon is
displayed to the right of the location in the list:
The location has been synchronized from the device to the server
There are changes to the local copy that need to be synchronized to the server
The location belongs to a different user account: it can only be synchronized when
signed in to the owning account. You will only see this if you use multiple different
Crookneck Photo Apps with Location Synch on the same device.
Note: you will need to press synchronize to pull changes from the server down to the device,
as well as to push changes from the device up to the server.
Exporting Locations
You can export your locations from TPE as a KML file. KML (Keyhole Markup Language) is a
text-based file format widely used to share geographic information between applications.
To export your locations, tap the action button at the top of the Locations list. Choose
"Export Locations". Once exported, you can email the KML file to an address of your
choosing.
Importing Locations
You can import locations from a KML or KMZ (zipped KML) document by sending the file as
an email attachment. Open the email on your iOS device, and then open the attachment in
TPE (you may need to choose Open In…, then TPE). TPE will prompt you to ask if you want
to import locations from the file. If you choose Import, any locations found in the document
will be added to your locations list.
Note
Not all KML files will contain locations that TPE can import. Specifically, TPE looks for
Placemark entries in the KML document that include latitude/longitude coordinates.
Warning
TPE does not attempt to detect duplicate locations in any KML file that is imported. If
you import the same file twice, you will see duplicate locations in your list.
You can remove duplicate locations by choosing Delete duplicate locations in
the Settings screen.
Visual Search
Visual search provides a quick and simple way to find a date when the sun or moon will appear
at an azimuth and altitude you specify.
Visual Search offers two modes, Basic and Advanced:
In Basic mode, the following options are available:
Body
Choose sun or moon
Choose any, crescent, full or custom
Crescent corresponds to when the moon is between 0% and 15%
Illumination
illuminated; full to when it is between 95% to 100% illuminated. These
values are preselected to correspond to typical perceptions of what
appears 'crescent' or 'full', rather than the precise astronomical
definitions.
Illumination
If moon is selected and illumination is set to custom, enter the desired
range %
custom illumination range here
Choose Rise/Set or Az/Alt
Find
Rise/Set requires only an azimuth as input, whereas Az/Alt allows you to
specify both azimuth and altitude
Target
altitude °
If Az/Alt is selected, enter the target altitude above the horizon
Target
Enter the target azimuth relative to either true north or magnetic north,
azimuth °
depending on the app settings
Tolerance
±°
In basic mode, this refers to the allowable tolerance in azimuth.
Start date
The date from which to start the search
Duration
The period of time for which to search
Perform
search
Tap this to perform the search
Setting search parameters visually
You can set the target azimuth and altitude visually using the secondary map pin
(hence 'visual search').
With geodetics enabled, and the secondary map pin positioned, the target azimuth
and altitude fields are populated automatically from the geodetics results, making it
simple to drop the pin behind some mountains, navigate to visual search and find
when the sun will above just on the highest point along the line of sight.
All searches are performed for the current primary pin location, so ensure that is set to the
desired location beforehand.
Rise/Set search will check rise/set times, adjusted for elevation above the horizon if configured,
for the duration of the search and returns any matches that fall within target azimuth
tolerance.
Az/Alt search will find times when the sun or moon lies at the target altitude and returns any
matches that fall within target azimuth tolerance. In almost all cases, the target altitude is found
to within 0.25° or better.
When Advanced mode is enabled, the following additional options are shown:
Choose Any, Waxing or Waning
Phase
For example, to find only truly 'new' moons, choose Crescent and Waxing.
Choose Any, Best, Civil or Custom
This setting restricts results for Moon searches based on the altitude of the
During
sun. Best corresponds to when the sun is between +2% and -2% altitude, i.e. the
time right around sunset. Civil corresponds to a sun altitude between 0° and
-6°, that is, the period of civil twilight.
This setting adjusts the search to account for the apparent disc size of the sun
or moon when finding altitude. For example, if you want to find times when
Align
the moon appears to be 'sitting' on top of a building, you would align to the
disc
bottom of the disc rather than the centre. The adjustment takes into account
variations in the semidiameter of the sun and moon through the year (e.g.
'supermoon' is 14% larger than 'micromoon').
Choose Altitude or Azimuth.
When altitude priority is selected, the algorithm finds matching altitudes and
then tests azimuth. With azimuth priority, azimuth is found and then altitude is
Priority
tested against the target and tolerance.
Consider changing priority to match whichever alignment is the most critical
for your shot. For example, to catch the moon rising above a mountain peak,
altitude is likely more important than azimuth. To align the moon directly
behind a statue, azimuth is likely the most important consideration.
The result page lists all matches found for the search period. All results shown match the input
parameters and tolerance. Results that match the input targets within 0.25° are highlighted
with a green icon. Tap any result to set the selected date and time and view the result on the
map.
Note
Not all searches will generate results. You will never find the sun rising due north in
London, for example. Not all input parameter combinations are valid: you will never
find a waxing crescent moon rising at 90° during civil twilight. A basic understanding of
moon phases can help you to set up search parameters correctly.
You may wish to increase the tolerance above the default 2° if you have trouble
obtaining results. For reference, the approximate apparent diameter of the sun or
moon is 0.5°, hence a tolerance of ±2° corresponds to ±4 sun/moon diameters. Equally,
you can reduce this tolerance for shots that require a tighter alignment.
Tip
If planning a shot that requires a specific sun or moon alignment, you may find few
results if the tolerance is set too tight.
Always consider what flexibility in shooting position is available to you.
For example, azimuth alignment is critical in order to align the moon behind a statue.
However, you may be able to obtain the desired shot with a range of possible altitudes
by moving closer to or farther from the subject.
Az/Alt searches work by interpolating the 'priority' input (altitude or azimuth) to obtain, a high
accuracy match (within ±0.05° in most cases). The corresponding input (e.g. azimuth in the
case of altitude priority), is then inspected and tested against the target value and tolerance. As
noted above, you can choose priority based on your planned shot requirements.
However, in specific circumstances, on mode may give better results than other, based on the
rate of change of the values through the day. For example, an azimuth priority search in
Singapore in the middle of the day may work less well than an altitude priority search, as the
azimuth of the sun or moon tends to change extremely quickly as the body passes overhead.
Shadows and Elevation Adjustments
The app will determine the length of shadows cast on flat ground by both the sun and moon
for different times of day for an object of arbitrary height.
Specify a primary object height such as the height of a building, and the app will display
the length of the shadow cast by both sun and moon for the selected date/time and primary
pin position.
Note
Shadow lengths assume flat terrain - the actual shadow length may vary significantly
from the displayed value on sloping terrain. You can check to see if the terrain is flat
using topographic maps or the geodetics function.
Note
Moon shadows are only visible when the sun is set and, in most cases, only in dark
areas at times when the moon's disc is sufficiently illuminated (i.e. not at times of new
moon).
As noted above, if the primary object height is set, then the radius of the +6° shadow circle is
adjusted to match the length of shadow cast by an object of the height specified when the sun
or moon is at +6° altitude. If the object height you enter is small (e.g. 10 feet), then the circle
will appear very small on the map and may not be visible without zooming in.
As an example, you might set the object height equal to the known height of a building. TPE
will then display the length of shadow cast by the sun or moon for the selected time of day. To
view the sun or moon directly behind the top of a building at a specific time, you would plan
to position the camera at the end of the shadow line shown on the map.
A further use for the primary object height is to set the height of the camera above the ground
for situations where your shooting location corresponds to the primary pin. The geodetics line
of sight analysis accounts for the primary object height calculating visibility from primary to
secondary pin.
Secondary object height
In addition to setting a primary object height, you can set the secondary object height. You
would typically use this instead of, or in conjunction with, the primary object height when
planning a shot with the sun or moon juxtaposed or on top of a building, for example, a full
moon right next to the top of the Eiffel Tower.
In this situation, sun or moon position should be calculated for the shooting location, so the
camera position corresponds to the primary pin. The building or landscape feature that the
sun or moon will be set against then corresponds to the secondary pin. In the example of the
Eiffel Tower, you would specify the secondary object height as 986 feet or 300 metres.
This object height is then displayed in the geodetics charts and is accounted for in calculating
the maximum altitude along the path from primary to secondary pins. This makes is very
simple to use Visual Search (above) to determine when the sun or moon will be positioned
directly behind the top of the tower. (You may of course, choose to adjust the target altitude
or azimuth in Visual Search to place the sun or moon just to the left or below the top of the
structure, rather than directly on top of it.)
Note
If primary and/or secondary object heights are specified, if you use the pin swap
function on the map, the object heights are also swapped such that they remain with
the geographic position with which they were previously associated - i.e. they don't
move with the map pin during a swap.
Elevation offset
Optionally, you can apply a manual correction or offset to the reported elevation data used by
the app. This may be desirable in areas where the accuracy of the elevation data is poor.
Background
Elevation data is obtained from web services, principally Google Elevation and
GeoNames SRTM3. While usually accurate, you may find the data is less than perfect in
certain areas. (One example recently found is Golden Cap in Dorset, England, where
the reported max elevation is some 100 feet lower than the true elevation.)
For shots requiring critical alignments, always double check the reported elevation data
against a known reliable source, e.g. USGS topographic maps in the USA, or Ordnance
Survey maps in the UK, and apply corrections using the elevation offset fields.
Any elevation offsets you enter are applied as a weighted average along the path from primary
to secondary pin when showing the elevation or altitude profile.
Elevation above Horizon
Sunrise occurs sooner when standing on top of a mountain looking east over a plain, due to
the height of the observer above the horizon.
Optionally, TPE can account for this effect by allowing you to specify the elevation above sea
level at the horizon. Either touch the text field to enter a value directly or place the secondary
pin (grey) and TPE will find the elevation at that point and enter it into the field for you.
When enabled, the theoretical distance to the visible horizon from the primary location is
displayed. This value can be calculated from the difference in elevation together with the
curvature of the earth and the effects of atmospheric refraction.
In addition, the dip of the horizon is shown: this is a measure of how much the horizon is
depressed because of the observer's elevation above the ground. A positive value, e.g. +1.1°
indicates that the horizon is lower than normal by that amount. The higher the observer is
above the horizon, the greater the dip of the horizon. The dip of the horizon is used to adjust
the altitude at which rise or set is determined to occur. The higher above the horizon you are,
the sooner you'll see the sun rise.
If you set elevation at the horizon using the secondary pin, but the distance between the pins
is significantly different from the distance to the horizon, you may want to adjust the
secondary position to make the distances match more closely for more accurate results.
Once set, times of sun/moon rise/set are adjusted for the height above the horizon implied by
the difference in elevation from the primary pin. An overlay is displayed on the map showing
the distance to the horizon. Remember that the distance to the horizon will vary based on
direction. The distance shown is based on the elevation at the horizon that you have specified.
Tip
The horizon adjustment is only meaningful when the primary location (red pin) lies
above the horizon, i.e. the Elevation at horizon value should be less than the elevation
at the primary pin. Examples might include standing on a cliff looking out to sea; or
standing on the summit of a mountain looking out over the plains below.
In these circumstances, the observer's height above the horizon results in earlier
sunrises and later sunsets, for example, just as you see from an aircraft.
If you are trying to determine the effect of standing in a valley looking at a mountain
that is blocking the sun, then use Geodetics instead (described above).
Settings
The available settings are described below:
Select between Google and Apple. The offline map types
Maps
Map
(Open Street Map and Open Cycle Map Topographic are
available when Google is selected
Select between Satellite and Hybrid (default). If you prefer
Maps
Maps
Satellite
not to see map labels when using satellite maps, choose
maps
'Satellite'
Show current
location
When enabled, your device current location is shown on
the map at all times. This may consume additional battery
power.
Clear offline
Maps
map +
Select this option to delete offline map tiles and saved
elevation
elevation data from your device.
data
When enabled (default), the time zone at the primary pin
Time
Set
zone
automatically
location is determined automatically, if the device is
connected to the Internet. Set to off if you want to override
the automatically detected time zone. When disabled, you
can choose a time zone from the picker.
Imperial
General
(English)
units
General
Use magnetic
north
Enable to use feet/miles. Disable to use metric SI units (km,
m).
When enabled, all azimuths and bearings displayed in the
app are relative to magnetic north. Otherwise, they are
always relative to true north.
Google Elevation service includes bathymetry (sea floor
Minimum
General
elevation is
sea level
depth) if the path from primary to secondary pin cross
water. Typically this is not helpful to land-based
photographers. Enable this setting to pin the minimum
elevation to sea level. But remember to disable it if you visit
Death Valley or the shores of the Dead Sea.
Primary pin
General
is TPT
camera
iPad only
General
If geodetics are enabled, then when opening a shot in The
Photographer's Transit™, the primary pin is used as the
camera pin.
Clear offline
Tap this to remove any offline map tiles or elevation data
data
stored on your device.
Show
favorites on
On by default. Determines whether favorite locations are
Locations
Locations
map
always shown on the map.
Delete
Choose this option to find and delete duplicate locations in
duplicate
your saved locations list. The title, coordinates and notes
locations
fields are used to determine if a location is a duplicate
If you have previously synchronized your locations, use this
option to delete the data from the device. This function will
Locations
Clear
not delete any locations from your account on our servers
synchronized
and will retain any locations on the local device which have
data
not yet been synchronized. This function is 'safe': only
locations that are already sychronized to the server will be
removed from your device
Selecting this option will delete all locations from the local
Locations
Delete all
locations
device, and, if you are using location synch, will delete them
from your account on the server when you next
synchronze. This function is destructive: it will delete
locations from your device and account permanently
Analytics
Share usage
Enable to share basic usage data with the app developers -
data
see notes below for additional information
Notes
Open Cycle Map Topographic maps include topographic and cycle route information from
OpenCycleMap.org. Topographic maps are available between 60°N and 47°S. Outside these
latitudes, a non-topographic map is presented.
TPE uses the World Magnetic Model 2015 to calculate magnetic declination for the primary
pin location and selected date. Declinations are supported for dates between 2015-2020.
Outside of this date range, declination may be inaccurate.
Notice
Available map types are subject to availability from the respective map service provider.
Changes in terms under which a given map type is made available may result in the
removal, substitution or addition of map types with different versions of TPE.
Analytics information is sent anonymously. This information helps us understand how you use
TPE and assists us in continuing to improve it. No personally identifiable information is sent.
Note, we always log that TPE was started and if the app crashes or encounters an error
condition. No other diagnostics or usage information is collected. Please see our privacy policy
for additional detail.
Using TPE Offline
TPE can be used without a network connection, but with some limitations:
Built-in maps require a data connection
Offline maps will display any map tiles previously stored (see below)
Automatic timezone detection is unavailable - you can specify a time zone manually, or use a
saved location (see below)
Automatic detection of elevation above sea level is unavailable - mean sea level is assumed
Secondary pin functionality including Geodetics is unavailable (as elevation is required)
You can navigate to saved locations and the stored time zone and elevation data will be used. If
you have recently viewed the map for the location, you may find that map display is available
via your device's browser cache, but this should not be relied on (except as described below).
If location services are available, you can go to your current location, but map data will
normally be unavailable, unless viewed recently or previously viewed with an offline map type
selected. TPE will calculate all rise/set, twilight and detail azimuth/altitude information assuming
the location is at sea level. Geodetics and Horizon adjustment will be unavailable.
If TPE is unable to retrieve the correct time zone for the current primary pin position, you will
be prompted to specify a time zone manually.
Using Offline Maps
Certain map types support offline use. Currently, offline support is offered for OpenCycleMap
Topographic Maps and MapQuest OpenStreetMap.
TPE will store offline map tiles for up to a year, storage space permitting. If the offline map
store is full, then on start-up, TPE will delete the oldest tiles to reduce the store size.
If map tiles are stored offline, but your device has network connectivity, tiles are loaded first
from the store, then TPE checks with the original map tile server to see if any updated tiles
are available. If they are, the updated information is downloaded and the older version in store
is replaced.
Map tiles are stored in the application documents directory, rather than the caches directory.
This means that iOS will not delete them automatically if storage on the device runs low. This
is by design, to ensure that maps you want to be available offline are there when you need
them. Tap Clear offline data to delete the data manually.
DISCLAIMER
You should not rely on TPE as your primary means of navigation.
Offline map tiles are marked not to be backed up. They are excluded from device backups to
iCloud and iTunes. If you restore your device from backup, tiles that were previously available
offline will not be restored.
In summary, for offline maps, as long as there is space in your offline store, if you have viewed a
map tile on the device within the past 12 months, it will be available offline automatically.
Need support?
For support, please email us at [email protected]. You can also write to us using
the option within the app itself.
Notices
The Photographer's Ephemeris, Photo Ephemeris, The Photographer's Transit and Photo
Transit are trademarks of Crookneck Consulting LLC
Credits
Topographic maps by OpenCycleMap.org
MaqQuest tiles courtesy of MapQuest
MapQuest OpenStreetMap maps: © OpenStreetMap contributors, CC-BY-SA
Time zone and elevation data courtesy of GeoNames.org
Astronomical algorithms from Astronomical Algorithms, 2nd Ed. by Jean Meeus
Geodetic calculations based on T. Vincenty's work, adapted from implementations by Mike
Gavaghan and the US National Geodetic Survey
Distance to horizon calculation based on formula with refraction given by Andrew T. Young
Adjustment for height above the horizon taken from the Explanatory supplement to the
Astronomical Almanac by P. Kenneth Seidelmann
Crescent moon visibility calculations based on "A Method for Predicting the First Sighting of
the New Crescent Moon" by B.D. Yallop of HM Nautical Almanac Office
Magnetic declination derived from the World Magnetic Model (WMM2010)
Light pollution overlays from https://github.com/djlorenz/djlorenz.github.io
Many thanks to Jeff Conrad for his expert comments and advice on TPE since 2009
Thanks to Bruce Briegleb for his help and advice on implementing the Milky Way and major
constellations in Night Mode
Sincere thanks to our users and, in particular, our beta testers, for the suggestions,
comments and insights that have helped shape the app. In particular, Andrew, David, Peter,
Frank, Matt, Kenneth, Roy, Ken, Christian, Frans - thank you for your suggestions on 3.0 and
beyond!
The development of this app was caffeine-fuelled courtesy of Red Rock Coffeehouse,
Boulder, Starbucks and Caffè Nero, Gosforth
Wacht auf, es nahet gen den Tag;
ich hör' singen im grünen Hag
ein wonnigliche Nachtigall,
ihr' Stimm' durchdringet Berg und Tal:
die Nacht neigt sich zum Occident,
der Tag geht auf von Orient,
die rotbrünstige Morgenröt'
her durch die trüben Wolken geht.
© Copyright Crookneck Consulting LLC, 2010–2016. All rights reserved