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Coordinate Transforms

Coordinate Transforms. z. x. y. Equatorial and Cartesian Coordinates. declination (δ). Equator. right ascension (α). Equatorial and Cartesian Coordinates. x = Rcosα y = Rsinα. y. α. R. x. right ascension (α). y. declination (δ). z. r = 1. δ. R = rcosδ z = rsinδ. R.

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Coordinate Transforms

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  1. Coordinate Transforms

  2. z x y Equatorial and Cartesian Coordinates declination (δ) Equator right ascension (α)

  3. Equatorial and Cartesian Coordinates x = Rcosαy = Rsinα y α R x rightascension (α) y declination (δ) z r = 1 δ R = rcosδz = rsinδ R

  4. Precession • Because the Earth is not a perfect sphere, it wobbles as it spins around its axis • This effect is known as precession • In the last lecture, I noted that the equatorial coordinate system relied on the idea that the Earth rotated such that only α, and not δ, was a time-dependent coordinate

  5. The effects of Precession • Currently, the star Polaris is the North Star (it lies roughly above the Earth’sNorth Pole at δ = 90oN) • But, over the course ofabout 26,000 years avariety of different pointsin the sky will truly beat δ = 90oN • The declination coordinateis time-dependent albeiton very long timescales • A precise astronomicalcoordinate system must account for this effect

  6. Equatorial coordinates and equinoxes

  7. Equatorial coordinates and equinoxes

  8. Equatorial coordinates and equinoxes

  9. Rotations

  10. Rotations and Galactic Coordinates NP of Galaxy NP of Earth

  11. IDL tasks

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