Stellar Parameters such as their mass, luminosity, radius, Temperature, Metallicity (Z), age, rotation, and distance can occasionally be determined directly, but more values can be determined using models, varying from simple equations to charts reflecting many observed stars, and to simulations of stellar processes. Through a chain of such determinations, many parameters can be determined or approximated.
In some cases even when a parameter cannot be fully determined, a probability distribution of its values can be, which has value in studies of entire populations. For example, if the the viewing angle of a binary system's orbit is undetermined, the distribution of viewing angles is known so data from a population of such binary systems still reveals information about the distribution of parameters that the viewing angle would have revealed.
The most direct methods:
Less direct methods:
Binary Stars observed over time reveal much:
See Stellar Distance Determination, Stellar Mass Determination, Stellar Radius Determination, Stellar Luminosity Determination, Stellar Temperature Determination, Stellar Age Determination, Stellar Rotation, and Gyrochronology.
ATLAS Stellar Model