Celestial Navigation Made Easy


Making Observations

Take a Sight

After selecting the object to sight from the main screen, the sight screen will be presented which shows the current time and expected altitude of the object. Both are updated on the second if “Now” is selected from the time and date screens.

If your device has an internal compass, the object icon at the top of the screen will help you find the object in the sky.  Point your device until the icon of the object is centered in the “[  ]”, then look up by the current expected altitude and there it is!  Very helpful when finding stars. 

After taking your sight with the sextant, touch anywhere on the screen to stop the clock and mark the time.  The sliders will be positioned at the expected altitude to help minimize any changes to make.  Move the sliders (for big changes) or touch the “+” and “-” signs (to increment/decrement by one) until the displayed altitude matches the sextant reading.  Then press the “Enter Observation” button.

If you stopped the clock by mistake or just want to try again, press the “Restart Clock” button to continue.

After selecting the bodies to be observed, the ezSights application provides simple interfaces to enter, evaluate and edit the sights you make with your sextant.

Display Sights

After taking one or more sights, press the “Display” button on the bottom of the screen to show all sights for the object against the arc of the expected value at the current assumed position.

This screen will help you identify sights that are inconsistent with other sights taken.  You may want to exclude them from being used when finding your fix or delete them altogether (see below).

The screen is automatically scaled to allow the display of all observations for the object.

List Sights

Pressing the “Mode” button from any other observation screen will take you to a list of all observations for the object.  There are 4 list modes available in this screen that are toggled by pressing the “List/Mode” button while the screen is displayed.

Select/Deselect Values

In this mode, a checkmark is displayed by each sight.  Touching the sight will remove or replace the checkmark.  Sights that are not checked will be displayed in grey on the display screen and will not be used when finding a fix.

Add or Delete Observation

In this mode, the standard iOS add/delete interface will be displayed and a now observation can be manually added or deleted.

Edit Observation

In this mode, touching the observation will display a screen that allows the observation to be edited.  Correction values for the observation can also be edited.

Show Sight Reduction

In this mode, touching the observation will show the sight reduction data for the sight (see below).

Sight Reduction

The Sight Reduction data for the observation shows all of the calculated values used to perform the sight reduction.  Note that these will NOT match values as you would pull then from a Nautical Almanac.  The Nautical Almanac typical provides hourly data tables that are then corrected by other interpolation tables to get the value for the specific minute and second.  Only the computed values are shown for ezSights.

This can still be used to validate a manual sight reduction.  All of the main values including GHA, Dec, Ha, and Ho will still very closely match the values you would get in a manual sight reduction (and/or with the ezAlmanac app), but the altitude corrections for Ho and Ha will be broken out differently.

Note that the Hc value computed by ezSights is computed directly from the DR position and may not exactly match an Hc from an “assumed position” as done in a manual sight reduction or ezAlmanac.

Directly Add or Edit an Observation

Editing Observation Values

If an observation has been entered and you find you made a mistake, that observation may be edited.  Similarly, the corrections for an observation may also be edited.

Starting in release 1.1.4 correction data is saved on a per-observation basis.  This means that you can specify different correction values in cases such as a dip short sight using different shorelines at different distances, using different limbs on the sun and moon, or taking sights at different times with different temperature or pressure values.

Directly Adding an Observation

If the “+” button is pressed while in the Add/Delete mode, a new observation will be created that can be directly entered.

Before manually entering an observation, we recommend that you first set all of the basic data you can from the other interfaces including date, time zone, DR position, basic corrections, running fix corrections, and selected objects.  The screen to the right will then only need to set the time and altitude for each observation to be entered.