What is 81at in Sidereal Hours?

You are: Home > Time > Tropical Years to Sidereal Hours

What is 81 Tropical Years (81at) in Sidereal Hours (hr-sr)?

What is 81at in hr-sr? Convert 81 Tropical Years (81at) to Sidereal Hours (hr-sr) and show formula, brief history on the units and quick maths for the conversion.

Enter Tropical Years to convert to Sidereal Hours


Quick Reference for Converting Tropical Years to Sidereal Hours

Formula
hr-sr = at x 8789.81
Quick Rough Maths
To get the Sidereal Hours, multiply the number of Tropical Years by 8.8 thousand
Tropical Years (at) in 1 Sidereal Hour
There are 0 Tropical Years in 1 Sidereal Hour
Sidereal Hours (hr-sr) in 1 Tropical Year
There are 8789.81 Sidereal Hours in 1 Tropical Year

Unit Information

Tropical Year
/ˈtrɒpɪk(ə)l jɪə,jəː/
Symbol: at
Unit System: SI

What is the Tropical Year?

The tropical year is a unit of time that is a multiple of an SI unit. We have used the symbol at.

The average tropical year up to the year 2000 was 365.2422 days of 86400 seconds.

The phrase “tropical” comes from the Greek for “turn”; tropikos. Following this, and where the “turn” referred to is the same as that defining the tropics of Capricorn and Cancer (the extreme latitudes North and South where the sun can still appear directly overhead or perpendicular to the Earth’s surface); a tropical year is known as the time it takes the sun to complete a full cycle of seasons and return to the same relative position to the observer on Earth.

In 1627, Johannes Kepler used the findings of Tycho Brahe and Waltherus (the Rudolphine Tables) to establish the mean tropical year as 365 solar days, 5 hours, 48 minutes and 45 seconds.

Sidereal Hour
/sʌɪˈdɪərɪəlˈaʊə/
Symbol: hr-sr
Unit System: SI

What is the Sidereal Hour?

The sidereal hour is a unit of time used by astronomers and is derived from the SI unit system. We have used the symbol hr-sr.

1 sidereal hour is made up of 60 sidereal minutes. This is derived ultimately from the sidereal day which is the time taken (in solar seconds) for the Earth to complete one rotation with respect to a distant star or constellation.

The sidereal hour angle is used when calculating sidereal time which is actually the angle along the celestial equator; from where one stands to the great circle that travels through the March equinox and both celestial poles.


Conversion Tables for Tropical Years (at) to Sidereal Hours (hr-sr)