The terms Reference star, Check star and Comparison star refer to different types of stars used for specific purposes during the Phoranso photometric analysis.


A check star is a star which is used to assess the stability of the observing conditions. Phoranso measures the check star's brightness alongside the Target star(s) of interest. By monitoring the check star's brightness, we can identify variations in the observing conditions that might affect the measured brightness of the Target star. A check star helps to ensure that observed changes in the brightness of a Target star are due to the intrinsic properties of the target star and not the result of external factors.


Phoranso requires the presence of exactly one check star when doing photometry of a star field. Phoranso uses the convention to color an Aperture Ringset around a check star in blue.