The Hub

I've updated Orbital Calculator to v 2.0.5 for all you sci-fi writers.

What the update brings:
This allows you to calculate the synodic periods of two orbiting bodies. Synodic periods define how often low-energy transfers (such as a Hohmann transfer orbit - which the progarm can also calculate) occur. Synodic periods also occur between satellite orbits when trying to get to a specific satellite, or to a specific location in the geostationry orbit.

The program can calculate the synodic period either by using the distances of the two orbits plus the mass of the host gravitational mass, or by using the periods of the two orbits.

Additionally, the new version allows you to calculate the Schwarzschild radius of any gravitational mass. If the mass is smaller than the Schwarzschild radius, the Schwarzschild radius defines the location of the event horizon, and the space beween this and the gravitational mass (which doesn't have to be a singularity) is a black hole.

If it is a black hole, then there is a region of space outside the event horizon where photons of light are forced into an orbit, and this region is known as the photon sphere. For a Schwarzschild (non-rotating) black hole, there is a single photon sphere. A rotating black hole has two photon spheres, one outside the other, and they orbit the black hole in opposite directions.

Orbital Calculator will determine the radius of the single photon sphere when it calculates the Schwarzschild radius.

Info on the program and its features are available here (its free, and available for Windows and Linux):
https://philip-p-ide.uk/doku.php/blog/articles/software/orbital_calculator

The download page is here:
https://philip-p-ide.uk/doku.php/blog/aardvaark/downloads