From d54fe7c1f704a63824c5bfa0ece65245572e9b27 Mon Sep 17 00:00:00 2001 From: Joseph Hunkeler Date: Wed, 4 Mar 2015 21:21:30 -0500 Subject: Initial commit --- src/slalib/sun67.htx/node189.html | 160 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 160 insertions(+) create mode 100644 src/slalib/sun67.htx/node189.html (limited to 'src/slalib/sun67.htx/node189.html') diff --git a/src/slalib/sun67.htx/node189.html b/src/slalib/sun67.htx/node189.html new file mode 100644 index 0000000..a19516f --- /dev/null +++ b/src/slalib/sun67.htx/node189.html @@ -0,0 +1,160 @@ + + + + +SLA_UNPCD - Remove Radial Distortion + + + + + + + + + + + + +
+ +next + +up + +previous +
+ Next: SLA_V2TP - Direction Cosines to Tangent Plane +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_UE2PV - Pos/Vel from Universal Elements +

+

+

SLA_UNPCD - Remove Radial Distortion +   +

+
+
ACTION: +
Remove pincushion/barrel distortion from a distorted +$[\,x,y\,]$ to give tangent-plane $[\,x,y\,]$.

CALL: +
CALL sla_UNPCD (DISCO,X,Y) +

+

+
GIVEN: +
+
+ + + + + + + + + +
DISCODpincushion/barrel distortion coefficient
X,YDdistorted $[\,x,y\,]$
+

+
RETURNED: +
+
+ + + + + +
X,YDtangent-plane $[\,x,y\,]$
+

+
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: +


+
+
+

+ + + + + + + + + + + + + + + + + + + + + +
GeometryDISCO
astrograph0.0
Schmidt-0.3333
AAT PF doublet+147.069
AAT PF triplet+178.585
AAT f/8+21.20
JKT f/8+14.6
+


+
+
+

4. +
The present routine is an approximate inverse to the + companion routine sla_PCD, obtained from two iterations + of Newton's method. The mismatch between the sla_PCD + and sla_UNPCD is negligible for astrometric applications; + to reach 1 milliarcsec at the edge of the AAT triplet or + Schmidt field would require field diameters of $2^{\circ} + \hspace{-0.37em}.\hspace{0.02em}4$ and $42^{\circ}$ respectively. +
+
+ +next + +up + +previous +
+ Next: SLA_V2TP - Direction Cosines to Tangent Plane +
+Up: SUBPROGRAM SPECIFICATIONS +
+ Previous: SLA_UE2PV - Pos/Vel from Universal Elements +

+

+

+SLALIB --- Positional Astronomy Library
Starlink User Note 67
P. T. Wallace
12 October 1999
E-mail:ptw@star.rl.ac.uk +
+ + -- cgit