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Timeline

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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 to 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 EssentialsiPhone only Includes civil twilight and sun rise/transit/set.
Daylight + Moon Includes sun and moon rise/set, civil twilight, moon phase and crescent moon visibilty
Extended Daylight Includes sun rise/set/transit, civil and nautical twilight, and 'golden hour'

In Night mode, they are:

Night Default Includes moon and galactic centre rise/set, all twilight data, moon phase and crescent moon visibilty
Night Essentials Includes moon rise/set, nautical and astronomical twilight, moon phase
Night All 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 The moment at which the upper limb of the sun disappears below an unobstructed horizon
Moonrise The moment at which the upper limb of the moon appears on an unobstructed horizon
Moonset The moment at which the upper limb of the moon disappears below an unobstructed horizon
Astro start The start of astronomical twilight, when the centre of the sun's disc ascends above -18° altitude
Astro end The end of astronomical twilight, when the centre of the sun's disc descends below -18° altitude
Nautical start The start of nautical twilight, when the centre of the sun's disc ascends above -12° altitude
Nautical end The end of nautical twilight, when the centre of the sun's disc descends below -12° altitude
Civil start The start of civil twilight, when the centre of the sun's disc ascends above -6° altitude. Also known as 'dawn'.
Civil end The end of civil twilight, when the centre of the sun's disc descends below -6° altitude. Also known as 'dusk'.
Golden hour 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 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 quarter The moment of third (or last) quarter moon (when the moon is waning and half illuminated).
New moon The moment of new moon (when the moon is closest to the sun in the 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)
Crescent moon visibility Indication of visibility for the new moon. Possible indications include 'Try' (a telescope or binoculars is likely required) or 'Best' (moon can be most easily be observed at this time, with the naked eye). The letters A to F indicate the moon visibility classification according to the Yallop method.
Sun transit 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 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.
Moon transit The moon transit time, also referred to as moon-meridian transit time, is the time at which the moon passes over the observer's meridian line. It corresponds approximately to the moment when the moon is at its maximum altitude for the day.
GC rise The time when the galactic centre (the centre of the Milky Way) rises at the ideal horizon.
GC set The time when the galactic centre (the centre of the Milky Way) sets below the ideal horizon.
GC transit The time when the galactic centre (the centre of the Milky Way) crosses 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.

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