MithlondSE: Solar Energy Calculator

MithlondSE is an application that allows you to determine location of the sun at a particular point and time. Version 2.2 adds tides and the ability to print or save most of the views, including the main horizon view window. If you want to see some of the program output, checkout the almanac and some its subpages like the locations page.

For full year views be sure to load YearlyData.ydt that comes in the .zip rather than recreate it. Unless you change the topology or some of the render and resolution settings, there is no need to recreate this data. If you do recreate it on a 4 processor machine, be sure to up the thread count to 4 in the settings window.


Just download the .zip file and unzip where you want to run it. Note that you must have a default-topo.txt file which defines the initial world topology. The default and a sample user topology file are included in the .zip file. You can change the topology in that file or make your own .txt file and read it in from the settings menu command.

Note you can also access the file from the file link at the bottom of this page.

Implemented Features

  • The Render Buttons allow you to:
      • Render Time Renders the horizon and the location of the sun at a particular time.
      • Render Day Renders the horizon and the sun during the course of an entire day.
      • Render Month Renders the horizon and the daily arcs of the sun over a month.
      • Render Year Renders the horizon and the daily arcs of the sun over a year.
      • Rending Day or Time will display sunrise, sunset and daily energy information for that day.
  • Table views to set sunrise/sunset/energy and temperature for a month to a year. Table views can be printed.
  • WorldViews allow you to look at peak power, total energy, temperature and other items for a given day or for a full year.
      • You can save and restore world view data rather than recreate each run. The release comes with yearly data (YearlyData.ydt)
  • Settings menu option allows you to change:
      • World topology by loading a new topology file (txt format, see notes in the defaul-topo.txt file for format).
      • Steps sizes for the sun during the day for day, month and year renders.
      • Number of days between arcs for month and year renders.
      • You can also turn on and off various things like the angle bars, arc lines, sun time, etc.
      • Settings, including topology can be saved and restored.
  • WorldViews allow you to see the disc of the world annotated and colored for various options
      • Topography displays a top down view of the ridges and arcs defined in the topology file. This view also shows your current location which can be quite useful when making sense of the renders.
  • The Month Tables now show the height of the tide at the beginning of a day and a peak tide magnitude and tide if there is a peak in the day. There is also a tide table that shows the tides by hour for a given point for a week.
  • Cone objects to the allowed topography which is good for sticking at the end of ridges to make the ridge look more sensible in profile as view points are head-on to the ridge.
  • Left edge of the horizon view can be set by user. Default is now 90 degrees which works better with where the sun rises and sets throughout the year.
  • There is now a settings option to make the horizon partially transparent to better see what the sun is doing near sunrise/sunset.

Brief Help

The main view has an upper panel where the horizon and sun will be rendered and a lower panel where you enter the current location and time. Use the Table and WorldView menus to create tables for a particular location or look at the full world.

More Detailed Help


Program was written and tested with the assumption that all points on the surface of the world are below the height of the rim mountains. Default rim height is 200 miles so everything should be between 0 and 200 miles.

Interesting Observations

I currently have the default sun 200 miles across with a solar radius of 3000 miles. This makes for a large sun at times- as much as 15 degrees if you are near the edge of the world. The Earth moon is about 0.5 degrees for reference. We could make a smaller sun and still have a noticable change in its size. 15 degrees might be a little extreme- that's the same arc as holding a one foot ruler at about 3.7 feet from your eyes.

If you are near the edge of the world, weird things can happen such as the sun can be very large or very small at times or the sun can trace a path in the sky that first moves to the west the back to the east overhead, then west again. Play around with points near the edge of the world.

Troubleshooting Tips

Change Log Details

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