# How does declination and right ascension relate to latitude / longetude?

• Sqw
In summary: Latitude is measured from the Equator to the North Pole.Right Ascension is measured from the Prime Meridian - which is the line that divides the Eastern from the Western Hemispheres - to the North Pole.
Sqw
It seems to me declination lines are vertical like longitude, and coordinates is measured horizontally (but if it runs vertical than how could it be measured as 0° at the equator?), and right ascension lines run horizontal like latitude with coordinates measured vertically.

However this doesn't seem to be the case so I need some clarification.

What directions do the declination and right ascension lines actually run? and where do their 0 degrees/hours begin?

Hi Sqw!

No, declination (as the name suggests) is angle above the celestial equator, equivalent to latitude (and is 0 at the celestial equator), and right ascension (silly name) is equivalent to longitude (and is 0 at the vernal equinox), see http://en.wikipedia.org/wiki/Equatorial_coordinate_system

Latitudinal Lines run North-South.

Longitudinal Lines run West-East.

They are fixed to the planet.

Declination Lines run North-South but begin at the Ecliptic Plane but is fixed in the celestial Sky.

The Ecliptic Plane varies depending what time of year it is will be -20 to 20deg from the Equator.

Right Ascension run West-East on that plane also fixed in the sky and varies due to the time of day.

Philosophaie said:
Latitudinal Lines run North-South.

Longitudinal Lines run West-East.

They are fixed to the planet.

lines of latitude run east west -- parallel to the equator :)

and opposite for lines of longitude

Dave

Latitudinal Lines run North-South.
Longitudinal Lines run West-East.

I stand corrected.

Longitudinal Lines do run from North-to-South. Increasing in magnitude from West-to-East. Are based on Terra Firma, Earth.

Right Ascension Lines run from North-to-South. Increasing in magnitude from West-to-East. Are based on the Ecliptic Plane(the angle the Earth orbit makes with the Sun) and are fixed in the Sky. Right Ascension is based on the Longitude, the time of day, timezone, daylight savings time and the Local Mean Sidereal Time which equates it with the Vernal Equinox on the Ecliptic Plane.

Latitudinal Lines do run from West-to-East. Increasing in magnitude from North-to-South. Are based on Terra Firma, Earth.

Declination Lines run from West-to-East. Increasing in magnitude from North-to-South. Are fixed in the Sky. The magnitude is simply equal to the Latitude.

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## 1. What is declination and how does it relate to latitude?

Declination is the angular distance of a celestial object from the celestial equator. It is measured in degrees, with positive values representing objects north of the celestial equator and negative values representing objects south of the celestial equator. Declination and latitude are directly related, as they both measure the angular distance from the equator. However, declination is specific to celestial objects, while latitude is specific to locations on Earth.

## 2. How is right ascension related to longitude?

Right ascension is the angular distance of a celestial object eastward from the vernal equinox. It is measured in hours, minutes, and seconds, with a full circle being 24 hours. Right ascension and longitude are both measures of angular distance, but they are not directly related. Right ascension is specific to celestial objects, while longitude is specific to locations on Earth.

## 3. What is the relationship between declination and right ascension?

Declination and right ascension are both measures of angular distance, but they are independent of each other. Declination measures the distance from the celestial equator, while right ascension measures the distance from the vernal equinox. Together, they can be used to pinpoint the location of a celestial object in the sky.

## 4. How does declination and right ascension help us locate objects in the sky?

Declination and right ascension are used as coordinates on the celestial sphere to locate objects in the sky. They act as the equivalent of latitude and longitude for Earth, allowing us to pinpoint the position of celestial objects from any location on Earth. By knowing the declination and right ascension of an object, we can use star charts or computer programs to find its exact location in the sky.

## 5. Is declination and right ascension constant for all celestial objects?

No, declination and right ascension are not constant for all celestial objects. They are specific to each object and change as the Earth rotates on its axis. However, they are constant for a specific object at a given time. This means that the declination and right ascension of a star or planet will be different depending on when and where it is observed from on Earth.

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