Ephemeris Interpolator can launch the desktop application Google Earth Pro to display an area of the sky centred on the calculated RA and Dec by pressing the Display Position in Google Sky button on the main Ephemeris Interpolator and also the Pad window.


Install the Google Earth Pro on Desktop application - see the link on https://www.google.com/intl/en_uk/earth/versions/ page.

Configure the setting GoogleSkyFieldSize. This allows the field of view displayed in Google Sky to match the size of your telescope field of view. The Display Position in Google Sky button is disabled if the field size is set to 0.

Display a position in Google Sky step by step

When the Display Position in Google Sky button is clicked the Ephemeris Interpolator creates a KML (Keyhole Markup Language) text file containing information about the calculated position and uses that file to launch Google Earth Pro. When Google Earth Pro starts it recognises that the KML file describes part of the sky and prompts the user:

Click the Switch to Sky button to switch Google Earth Pro into Sky mode.

Make sure the Sidebar is visible (tick Sidebar in the View menu, or press Ctrl+Alt+B)

In this example, in the Places section of the Sidebar, the kml file appears within Temporary Places for an object called A10FTIV:

Double click the entry in Temporary Places to centre the Google Sky view at the calculated position, with the field of view set to the GoogleSkyFieldSize setting. In this example, a pushpin marks the exact position calculated for the date and time (@09:18:00) and the field of view is set to 0° 18' 24" (the GoogleSkyFieldSize was set to 18.4):

If the pushpin is clicked more detailed information is displayed, for example:

GoogleSky KML template

The information shown for a pushpin and its formatting is defined in the KML file that the Ephemeris Interpolator creates when the Display Position in Google Sky button is pressed. The KML file is generated from a KML template file stored internally in the Ephemeris Interpolator.

The KML template file can be edited if different formatting of the pushpin data is desired by using the Edit GoogleSky KML template button. This opens the KML template file for editing with Windows Notepad, or an external text editor if the TextEditor setting has been configured. When any changes have been completed, save the file. If the KML template file is deleted, or saved with no content, the next time the Edit GoogleSky KML template button is pressed a new template will be recreated automatically.

Substitution variables

When a temporary KML file is created it translates substitution variables in the KML template into the values calculated for the current object. Substitution variables are always surrounded by { } brackets, are not upper or lower case sensitive and are available for the following data items:

Substitution variable

Translates to


{ObjectName}@{Time} (with time in hh:mm:ss format)


Object name


RA converted to -180 -> +180, to 7 decimal places


Dec -90 -> +90, to 7 decimal places


RA in HHh MMm SS.Ss format


Dec in +dd° mm' ss format


Date in yyyy-MM-dd format


Time in HH:mm format


R*(k*sin(beta/2) - cos(beta/2) + 1)   *see technical information


Speed to 2 decimal places


P.A.° to 1 decimal place

* For technical information on KML files see https://developers.google.com/kml/documentation/kmlsky.

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