Guildford Astronomical Society

Astronomy Applets and Applications

This page gives links to useful astronomical applications and applets that are available within the public domain.
Some apps will load directly and others will require downloading and installing before they can be run.

Constellation Viewer v2.3 (Sept 2018) – This is the latest version by John Hodder, of Guildford Astronomical Society

This application has been written by GAS member John Hodder. Its aim is to help familiarize observers with the night sky constellations.

The program displays a projection of stars in the selected constellation, with options to show the star names (where known) and the official designations. The sizes of the stars can be adjusted, brighter stars always looking larger; the font size for the star names and designations can also be adjusted.
Zooming is possible via the “Scale” slider.
The “Magnitude limit” box allows faint stars to be ignored.
Clicking in the centre of any star will show its name, magnitude, distance and designation.
The “StereoPair” button lets you view the constellation in 3D to give an impression of the stars’ distances.

New for version 2.3
– The names of nearby constellations can be displayed.
– Constellations can be selected by English name from a new list.
– The view can be scrolled by dragging with the mouse, or touchpad swiping.
– Messier deep-sky objects can be displayed and listed.
– Lists can now be sorted by clicking on column headings.
– More advanced facilities are obtainable via a new More button.

This program is written in Java, so you will need Java installed on your computer (just the Java JRE download).

To download the ConstellationViewer2.3 zip file Click here then ‘Extract All’ and you should see just one file inside it:
ConstellationViewer2.3.jar the java program executable (includes the star data).

To run the program, double click on the file ConstellationViewer2.3.jar, which should run if you have the Java runtime installed on your computer.

screen-shot v2.3

Once the program is running there is a comprehensive help via the [Help] button.

Eclipsing Binary Simulator – The University of Nebraska-Lincoln

Can also be used to simulate exoplanet transits.
This simulator (click here to load) is part of the Eclipsing Binary Module of the Nebraska Astronomy Applet Project. Supporting materials and additional astronomy education resources can be found at
Funding for this work was provided by NSF grants #0231270 and/or #0404988.  Permission is granted to use this file for noncommercial purposes as long as it remains unmodified.


The Project site has a number of interesting astronomical educational and demonstration videos that can be found at

Will require Adobe Flash Player to be installed.

AstroClockFX by Joseph J. Novak

This very useful astronomy clock displays the current local & UTC date & time, a calendar, local & Greenwich sidereal times, and the Julian day. The menu items also include current data for the sun, moon, planets, eclipses, and other Solar System information plus event timers.  The algorithms used are based on Jean Meeus book “Astronomical Algorithms”.  Planetary images are generated by the JParsec Astronomical Library by T. Alonso Albi – OAN (Spain).


The clock can be downloaded where installation details are also given.
Will require Java8 – read the ReadMeFirst.txt file when the zip file is unzipped.