A top down view of the sun and two planets is shown in the upper window, and the appearance of the target planet from the observer planet is shown in the bottom window.
Use the planet selection dropdowns on the right to simulate views from different planets in our solar system, or use the sliders to select arbitrary distances from the sun.
Run the simulation using the Play / Pause button, or click and drag the planets into different positions.
About text
This simulator is an HTML5 reimplementation of and expansion upon the Phases of Venus simulation that was originally developed as part of the Nebraska Astronomy Applet Project.
The original simulation, along with related teaching materials, may be found at:
https://astro.unl.edu
This simulator is part of the Foothill AstroSims project, which is aiming to reimplement, in HTML5, Flash-based simulations that are used in Foothill Astronomy courses.
Similar projects include work done by Nik Nyby at Columbia University (https://github.com/ccnmtl/astro-simulations) and Kevin Ditts at the University of New Mexico (https://physics.unm.edu/Courses/Rand/applets/).