PC2MODEL

Name

pc2model

Purpose (one Line)

Generate synthetic PSF images for the HST WFPC2 Planetary Camera.

Description

A generated PSF is added to the output array. If the array is not
defined, it is created with dimensions 800 by 800. Successive calls
will add objects (PSF's) to the array.

Calling Sequence

pc2model, xsrc, ysrc, inten, filter, bmvnum, back, image

Inputs

xsrc, ysrc : Position of the PSF in the output array.
inten : Intensity of PSF relative to TinyTim output PSF
filter : Filter name in the form Fxxx(W,LP,M,N).
bmvnum : B-V list value (TinyTim V6.2 values):
BMVNUM TYPE B-V
1 O5 -0.34
2 O8F -0.32
3 O6 -0.31
4 B1V -0.27
5 B3V -0.21
6 B6V -0.12
7 A0V -0.04
8 A5V 0.12
9 F6V 0.37
10 F8V 0.48
11 G2V 0.56
12 G5V 0.66
13 G8V 0.75
14 K4V 0.92
15 K7V 1.28
16 M1.5V 1.45
17 M3V 1.44
back : Background to be added.

Keyword Parameters

DISTORT : If set the input x,y are taken to be in an undistorted reference
plane. They will be converted to the instrumental (distorted)
frame before generating the psf's for the model image, which is
in distorted space as always.
GRID : Grid spacing for psf files.
HSTPATH : Alternate path for HST PSF's.
JITTER : If set contains the gaussian smearing to apply to the image.
This is in units of 1/e half width. If not set, no smearing
is applied. This calculation is done in double precision
or float according to the type of image. The values passed
to the exp function ( e - (((x/j)^2 + y/j)^2/2)) are
restricted to a maximum based on the computational precision
to avoid floating point underflow.

NEW : If set, clears the output array to zeros before building the
PSF image(s).
OBJRAD : Radius of object in pixels. If not set, assumed to be a point
source. If set and radius is greater than 0.5, then PSF is
convolved with a circular function of this radius. This models
the object as a Lambert disk, crude but useful for barely
resolved objects.
PSFSIZE : Size of requested PSF, in arcseconds (default: 5).
SAMPFACT : Sample factor (default: 3).
VERBOSE : If set, prints informational message.
Z4 : setting for fourth (focus) Zernicke coefficient. If not set,
the default value for the WFPC2 instrument generated by HSTPSF
will be used.

Outputs

image : The image array into which the PSF is placed.

Common Blocks

Side Effects

Restrictions

Procedure

The Tiny Tim programs are used, via the procedure HSTPSF, to generate
a (usually) 2X (7.5 micron spacing) PSF at the nearest grid location to the
requested position. (This grid and default spacing are defined in hstpsf).
From the interpolated maximum returned by hstpsf, shift amounts for x
and y are computed.
The PSF is shifted by these amounts and then compressed to a 1X
(15 micron spacing) PSF.
Finally, the resulting PSF is multiplied by the intensity parameter and
added into the output array.
Calls external procedures BADPAR, BOXM, HSTPSF, and SSHIFT2D.

Modification History

Written by Peter L. Collins, Lowell Observatory, June, 2007.
Based on p6model.pro by Doug Loucks.
2007/6/26, PLC, add keywords GRID, PSFSIZE, Z4. Rename x,y inputs
to xsrc, ysrc, to avoid JITTER clobbering.
2007/07/08, MWB, psf placement reworked (was busted from long ago).
2007/08/08, MWB, fixed minor bug when pasting psf near top and right edge
2007/09/05, MWB, changed to permit multiple calls on same output image.
Added pixel response function.
2007/09/12, PLC, provide DISTORT flag to use undistorted input x,y
to generate psf's in the usual distorted (instrumental)
frame.