SLA_PCD - Apply Radial Distortion   

ACTION:

Apply pincushion/barrel distortion to a tangent-plane $[\,x,y\,]$.

CALL:

CALL sla_PCD (DISCO,X,Y)

GIVEN:

DISCO pincushion/barrel distortion coefficient

$$[\,x,y\,]$$ X,Y D

RETURNED:

$$[\,x,y\,]$$ X,Y

NOTES:

1.

The distortion is of the form $\rho = r (1 + c r^{2})$, where r is the radial distance from the tangent point, c is the DISCO argument, and $\rho$ is the radial distance in the presence of the distortion.

2.

For pincushion distortion, C is +ve; for barrel distortion, C is -ve.

3.

For X,Y in units of one projection radius (in the case of a photographic plate, the focal length), the following DISCO values apply:

Geometry DISCO

astrograph 0.0

Schmidt -0.3333

AAT PF doublet +147.069

AAT PF triplet +178.585

AAT f/8 +21.20

JKT f/8 +14.6

4.

There is a companion routine, sla_UNPCD, which performs an approximately inverse operation.