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Transform sky coordinates to another frame

transform_to.Rd

Convert a sky_coord vector between supported coordinate frames.

Usage

transform_to(x, frame)

Arguments

x

A <sky_coord> vector.

frame

Target frame. Use icrs() or galactic().

Value

A transformed <sky_coord> vector.

Details

Supported transformations are:

  • icrs() -> galactic()

  • galactic() -> icrs()

If x is already in the requested frame, it is returned unchanged.

For icrs() <-> galactic() conversion, ERFA documentation states matrix-element precision at about 20 microarcseconds.

Use transform_to() (not transform()) for sky_coord objects.

Examples

x <- ra_dec(c(10, 120), c(20, -30))
x
#> <sky|icrs>[2]
#> [1] (10, 20)   (120, -30)

g <- transform_to(x, galactic())
g
#> <sky|galactic>[2]
#> [1] (119.2694, -42.79039515) (247.0829, -0.04805424) 

transform_to(g, icrs())
#> <sky|icrs>[2]
#> [1] (10, 20)   (120, -30)

# Pipe-friendly workflow
ra_dec(10, 20) |>
  transform_to(galactic()) |>
  transform_to(icrs())
#> <sky|icrs>[1]
#> [1] (10, 20)