LocalWcs

class lsst.pipe.tasks.functors.LocalWcs(colCD_1_1, colCD_1_2, colCD_2_1, colCD_2_2, **kwargs)

Bases: Functor

Computations using the stored localWcs.

Attributes Summary

name

Methods Summary

computeDeltaRaDec(x, y, cd11, cd12, cd21, cd22)	Compute the dRA, dDec from dx, dy.
computePositionAngle(ra1, dec1, ra2, dec2)	Compute position angle (E of N) from (ra1, dec1) to (ra2, dec2).
computeSkySeparation(ra1, dec1, ra2, dec2)	Compute the local pixel scale conversion.
getPositionAngleFromDetectorAngle(theta, ...)	Compute position angle (E of N) from detector angle (+y of +x).
getSkySeparationFromPixel(x1, y1, x2, y2, ...)	Compute the distance on the sphere from x2, y1 to x1, y1.

Attributes Documentation

name = 'LocalWcsOperations'

Methods Documentation

computeDeltaRaDec(x, y, cd11, cd12, cd21, cd22)

Compute the dRA, dDec from dx, dy.

Parameters

xSeries

X pixel coordinate.

ySeries

Y pixel coordinate.

cd11Series

[1, 1] element of the local Wcs affine transform.

cd12Series

[1, 2] element of the local Wcs affine transform.

cd21Series

[2, 1] element of the local Wcs affine transform.

cd22Series

[2, 2] element of the local Wcs affine transform.

Returns

raDecTupletuple

RA and Dec conversion of x and y given the local Wcs. Returned units are in radians.

Notes

If x and y are with respect to the CRVAL1, CRVAL2 then this will return the RA, Dec for that WCS.

computePositionAngle(ra1, dec1, ra2, dec2)

Compute position angle (E of N) from (ra1, dec1) to (ra2, dec2).

Parameters

ra1iterable [float]

RA of the first coordinate [radian].

dec1iterable [float]

Dec of the first coordinate [radian].

ra2iterable [float]

RA of the second coordinate [radian].

dec2iterable [float]

Dec of the second coordinate [radian].

Returns

Position Angle: Series

radians E of N

Notes

(ra1, dec1) -> (ra2, dec2) is interpreted as the shorter way around the sphere

For a separation of 0.0001 rad, the position angle is good to 0.0009 rad all over the sphere.

computeSkySeparation(ra1, dec1, ra2, dec2)

Compute the local pixel scale conversion.

Parameters

ra1Series

Ra of the first coordinate in radians.

dec1Series

Dec of the first coordinate in radians.

ra2Series

Ra of the second coordinate in radians.

dec2Series

Dec of the second coordinate in radians.

Returns

distSeries

Distance on the sphere in radians.

getPositionAngleFromDetectorAngle(theta, cd11, cd12, cd21, cd22)

Compute position angle (E of N) from detector angle (+y of +x).

Parameters

thetafloat

detector angle [radian]

cd11float

[1, 1] element of the local Wcs affine transform.

cd12float

[1, 2] element of the local Wcs affine transform.

cd21float

[2, 1] element of the local Wcs affine transform.

cd22float

[2, 2] element of the local Wcs affine transform.

Returns

Position Angle: Series

Degrees E of N.

getSkySeparationFromPixel(x1, y1, x2, y2, cd11, cd12, cd21, cd22)

Compute the distance on the sphere from x2, y1 to x1, y1.

Parameters

x1Series

X pixel coordinate.

y1Series

Y pixel coordinate.

x2Series

X pixel coordinate.

y2Series

Y pixel coordinate.

cd11Series

[1, 1] element of the local Wcs affine transform.

cd12Series

[1, 2] element of the local Wcs affine transform.

cd21Series

[2, 1] element of the local Wcs affine transform.

cd22Series

[2, 2] element of the local Wcs affine transform.

Returns

DistanceSeries

Arcseconds per pixel at the location of the local WC.