SLA_PCD

Apply Radial Distortion

ACTION:

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

CALL:

CALL sla_PCD (DISCO,X,Y)

GIVEN:

RETURNED:

NOTES:

(1)

The distortion is of the form $\rho =r\left(1+c{r}^2\right)$, 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 the inverse operation.