What is 55hr in Sidereal Hours?

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What is 55 Hours (55hr) in Sidereal Hours (hr-sr)?

What is 55hr in hr-sr? Convert 55 Hours (55hr) to Sidereal Hours (hr-sr) and show formula, brief history on the units and quick maths for the conversion.

Enter Hours to convert to Sidereal Hours


Quick Reference for Converting Hours to Sidereal Hours

Formula
hr-sr = hr x 1
Quick Rough Maths
Sidereal Hours and Hours are approximately equal
Hours (hr) in 1 Sidereal Hour
There are 1 Hours in 1 Sidereal Hour
Sidereal Hours (hr-sr) in 1 Hour
There are 1 Sidereal Hours in 1 Hour

Unit Information

Hour
/ˈaʊə/
Symbol: hr
Unit System: SI

What is the Hour?

The hour is a unit of time and is a multiple of an SI base unit with the symbol hr.

There are 60 seconds in a minute and 60 minutes in an hour. Consequently, there are 3600 seconds in an hour.

In a mean solar day, there are 24 hours.

Originally in the Middle East, the hour was defined as 1/12 of the day or night time. However, seasonal factors clearly affected all of these definitions and an average is used today to normalise and allow calculations.

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 Hours (hr) to Sidereal Hours (hr-sr)