Crescent observation trainer

Version of 2019-11-26, Martin Elsässer


I have written a small visual tool, to practise seeing / finding faint lunar crescents. These are often of very low contrast, compared to the surrounding sky. As with most things, practice and preparation can make things easier.
The tool allows to set the elongation and orientation of the crescent, the brightness and colour of the sky, the brightness gradient of the sky, the field of view and the color and brightness of the crescent.

Required environment

The programm requires a Java 5 runtime environment (JRE), which probably exists on most modern operating systems. If you do not have a JRE on your machine, you can download it for free from SUN: Select "Java Runtime Environment (JRE)", and click download. The next page will then allow you to select your operating system and download the actual installation files.

Download and documentation

Programm history

26.03.2008 Using supersampling to make the crescent smoother
25.03.2008 Initial version

Known limitations


Start screen, displaying a short description and list of keys.

The crescent revealed, by pressing the "r" key.

Daytime crescent, with blue sky.
Startup parameters: rSky=150 gSky=150 bSky=220 gradient=0 orientation=-45

Strong gradient, narrow field of view, big cescent left of the middle, pointing left.
Startup parameters: gradient=200 field=1.0 orientation=65.0

Wider field of view = smaller crescent (at the bottom).
Startup parameters: field=2.5

Back to the Mondatlas-Main-Page