Copyrights and licensing

While the data calculated and plotted by is intended to be useful and reliable, it comes with no guarantee of any kind. All risk arising from the use of this website and the data it provides is borne by the user. If you find any errors in the calculations, or wish to contact me for any other reason about, please get in touch at

The source code for amounts to about 1800 lines of PHP and javascript, and is copyright © Roger Wesson 2018. A full description will soon be available. The code uses a list of observatories adapted from sites.json from astropy, which is under a BSD license.

The header image was taken by me at La Silla. It is freely available under a Creative Commons license, as are many of my photographs of ESO sites.