What is Time: BJD

Barycentric Julian Day (BJD) time is the universal day and time at the center of the solar system and is crucial to many astronomically-relevant processes as well as other time scales.


What is an Ephemeris

A highly useful concept for applications in both Double and Variable Stars, an Ephemeris is an estimation of where/when a particular astronomical event will occur at a particular time in the future.

Basic Physics

Newton’s Laws

Serving as the foundation for classical mechanics, Newton's laws of motion help mathematically describe countless processes that are crucial to astrometric projects.

HR Diagram

The Main Sequence

The main sequence is defined by the HR diagram movement of a star fusing hydrogen into helium within its core, and understanding the relationship between the luminosity, temperature, radius and mass of stars on the main sequence allows us to derive useful information from a star's location on it.


Using AIJ for Double Stars

AstroImageJ (AIJ) is the industry standard for measuring exoplanet transits as well as accurately measuring double stars, and has quickly become a core component of the astronomical sciences. This video is a guide and reference for anyone using AIJ for double stars measurements.


What is Time: HJD

Heliocentric Julian Date (HJD) is the Julian Date corrected for the differences in the Earth’s position relative to the center of the Sun.


Double Stars Overview

By determining the gravitational or mutual orbit of two stars using astrometry, it is possible to derive stellar mass and consequently contribute to and refine contemporary astrophysical theories and knowledge.


What is Time: JD

Julian Dates (JD) are a continuous count of days, and fractions of days, since noon Universal Time on January 1, 4713 BC (on the Julian calendar)


What is an Epoch

An epoch is a particular time period, point in history, or a moment defined by a particular event, and is a moment of time used as a reference point for a time-varying astronomical quantity.



The result of countless different cultures naming the same stars, inconsistent star names have necessitated the need for a dependable and systematic method of stellar nomenclature based on the brightness of stars within any given constellation.


Parsecs and Light Years

Parsecs and light years are common measurements of distance to celestial objects, and the former is especially significant for its importance to scientific writing and its relationship with parallax.

Basic Physics

Kepler’s Laws

Kepler's laws of planetary motion are: the orbits of the planets are ellipses with the sun at one focus, a line from a planet to the sun sweeps over equal areas in equal intervals of time, and a planet’s orbital period (P) squared is proportional to its average distance from the sun (a) cubed