Astronomical Computation Tools

This is a folder for small astronomical computation tools that I have written.

The Coordinates Tool page gets several hundred hits a month, suggesting that amateur astronomers and others are interested in coordinate-transform and other small tools.

If you have needs for other tools that you can't find elsewhere, feel free to send requests to me at

Coordinate Tool

The Coordinate Tool will accept astronomical sky coordinates in several systems and epochs and calculate the values in all the other systems/epochs.

It is written in Javascript (no server-side) so it can be used stand-alone.

I created it because, while there are many web-sites that will convert between J2000.0 and B1950.0, or from arbitrary dates (e.g. there are no decent web-sites that will convert to/from Galactic Coordinates, especially the "Old Galactic Coordinates" that were in use before 1959 and used, e.g., in the Sharpless-2 Catalog paper in ApJ.