Changing Observer Location
LTVT function details.. Main Screen..
This form appears when you click the Set Location button in the Main Screen. The observer location affects the computation of the Sub-observer point (the "librations), its percent illumination and the information about the Moon's position and size that appears in the Main Screen's upper right corner. This form lets you alter that selection.
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1. The location can be either "Geocentric" (an imaginary observer at the center of a transparent Earth), or a physical location on the Earth's surface ("Topocentric" locations).
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2. For topocentric locations, the information regarding longitude, latitude and site elevation (relative to mean sea level) can be entered manually or selected from a drop-down list (which reflects entries saved in a text file on disk). If values are entered manually, the program will check, after every key stroke, if there is a matching entry in the current list.
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3. The current longitude/latitude/elevation data can be Saved as the default. The default location will be used the next time LTVT is started, and can be restored at any time by clicking the Restore Defaults button. The default location does not have to correspond to an entry in the drop-down box.
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4. If the current longitude/latitude/elevation data does not correspond to a saved data set in the drop-down box, a special message will appear there. The Add button lets you assign a name to this data, and the new name will subsequently appear in the drop-down box. Do not attempt to enter the new name in the drop-down box, as this will alter the data display before you click Add. Instead, simply click the Add button and the New Site Name input form will appear.
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For input information, the Falling Rain World Gazetteer is helpful if you know the name, but not the coordinates or elevation, of a site.
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A list of amateur observing locations more complete than that provided with the basic LTVT download is available on the Calibrated Full Disk Images page. It can be downloaded and substituted for the initial one, or edited at will:
- Observatory_List_complete.txt -- (19 kb; rev. 18 Jul 2011)
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The longitude/latitude/elevation data in the present form is automatically overwritten if you choose to Load a Calibrated Photo using the "Overwrite Date/Time/Location" or "Display at original scale and orientation" options. The new values will be those stored in the calibration data file.
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Controls similar to those in the present form appear in the observer location areas of the Moon Event Predictor, the Libration Tabulator and the Photo Times Search Window, except they do not have the Save as Default/Restore Defaults buttons. The locations used by the different forms are independent of one another: changing the location in one form does not change the location in any of any of the other forms. A name added in any form is added to the disk file, and as a result will appear in all the other drop-down boxes the next time those forms are opened.
This page has been edited 7 times. The last modification was made by - 
JimMosher on Jul 18, 2011 2:50 pm