When observing an eclipse in an eclipsing binary, or an exoplanet transit, (amateur) astronomers schedule their observations near the time of the (mid-)eclipse or transit event. This requires some a priori knowledge about the timing of the event. Peranso offers a convenient Ephemeris calculator, which calculates the Calendar date and (geocentric) Julian date of all such events, during a time interval determined by the user.

This tutorial explains the Ephemeris calculator, using a practical example. We want to know all mid-eclipse timings of the star V Sge1 for  the period from Jul 1st till Jul 5th, 2021.

(1) V Sge is a variable star belonging to a subtype of close-binary supersoft sources (CBSS), which are not detected as supersoft X-ray emitters because the soft photons are absorbed by stellar winds or by the interstellar medium. In addition, it is an eclipsing binary system, with eclipses that are easily detected from Earth.