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Time

What is an Ephemeris

An Ephemeris is an estimation of where/when a particular astronomical event will occur at a particular time in the future. These can be provided in tables, formulas, and graphical depictions. The following will outline examples from Double Stars and Variable Stars.

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Calculating Besselian Epoch

This lesson will show how to convert image dates to Besselian, which is the recognized standard for Double Star research.

What is Time: BJD

Barycentric Julian Day – The current day and time at the center of the Solar System. A Barycenter is the center of mass between two objects. From the combination of Kepler and Newton, we know that objects orbit around a common Focus within an Ellipse. The more massive...

What is Time from an Astronomical Perspective

Here is a loaded question: What time is it? In Astronomy there are a variety of time scales. You will encounter a fair number of them. This video will outline some of these most common ones you will experience.

What is Time: HJD

In our continuing discussion on “What time is it?” we introduce 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. This accounts for the effects of the speed of light given...

What is Time: JD

Understand Julian Dates, how they are used, how they were founded.

What is an Epoch

Epoch is a particular time period, point in history, or a moment defined by a particular event. For Astronomy, it is an arbitrarily fixed instant of time or date. Examples: Planetary orbits, RA & Dec coordinates