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Last modified: Tue Jul 11 20:43:07 2006.
NAME:
centrod
PURPOSE: (one line)
Compute center of mass of an object aperture and errors.
DESCRIPTION:
CATEGORY:
CCD data processing
CALLING SEQUENCE:
centrod_err, image, image_err, xcen, ycen, $
radius, inradius, outradius, skyback, $
xbar, ybar, counts, xbarerr, ybarerr, countserr
INPUTS:
image : CCD image array.
image_err
xcen, ycen : Center of window.
radius : Radius of window.
inradius : Inner radius of sky annulus.
outradius : Outer radius of sky annulus.
skyback : Sky background in counts per pixel.
OPTIONAL INPUT PARAMETERS:
KEYWORD PARAMETERS:
ADDNEG : Flag, if set, the position is computed using both
the moments of counts above and below the background.
Default is to compute the position only using those
image values greater than the sky background.
OUTPUTS:
xbar, ybar : Position of center of mass.
counts : Mass of object in counts.
xbarerr, ybarerr : Error in position of center of mass.
countserr : Error in mass of object in counts.
COMMON BLOCKS:
SIDE EFFECTS:
RESTRICTIONS:
PROCEDURE:
MODIFICATION HISTORY:
Ported by Doug Loucks, Lowell Observatory, 1992 Oct, from the C-
language version written by Marc Buie.
4/1/93, DWL, Added argument validation (badpar).
99/08/31, MWB, added ADDNEG keyword.
2006 Jan 31 LAY Added errors (based on centrod)
(See astrom/centrod_err.pro)
NAME:
sumannerr
PURPOSE: (one line)
Integrate over an annulus.
DESCRIPTION:
This procedure computes the first two image moments of the pixels
contained within the input annulus AND THEIR ERRORS.
The position and inner and outer
radii define the annulus. Each pixel in the input image is then
assigned a weighting value which is its areal overlap between the pixel
and the annulus. This weight varies from 0 to 1 and is the precise
analytic area of overlap (computed by pixwt.pro). Of course, this
program doesn't do the computation for all pixels, only those near
the edge.
UNLIKE IN SUMANN, the moments are NOT into two components
CATEGORY:
CCD data processing
CALLING SEQUENCE:
Sumannerr, image, imageerr,xcen, ycen, $
inradius, outradius, back, backerr, totweight, $
sum, xmom, ymom, $
sumerr, xmomerr, ymomerr
INPUTS:
image : CCD image array.
imageerr : std deviation of image
xcen,ycen : Center of annulus.
inradius : Radius of inner circle.
outradius : Radius of outer circle.
back : Background to subtract from each pixel.
backerr : error in background
OPTIONAL INPUT PARAMETERS:
KEYWORD PARAMETERS:
OUTPUTS:
totweight : Area of annulus.
sum : Sums of positive and negative pixels.
xmomm : x moments relative to xcen.
ymom : y moments relative to ycen.
sumerr : formal error in sum
xmomerr : formal error in xmom
ymomerr : formal error in ymom
COMMON BLOCKS:
SIDE EFFECTS:
RESTRICTIONS:
PROCEDURE:
MODIFICATION HISTORY:
Ported by Doug Loucks, Lowell Observatory, 1992 Oct, from the
C-language version written by Marc Buie.
April, 1993. DWL. Replaced the inner FOR loop with vectors.
98/09/21, MWB, optimizations
98/09/29, MWB, fixed nasty bug introduced during optimization.
06/01/31, LAY, removed pos and neg sums, added errors, based on subann
(See astrom/sumannerr.pro)
NAME: wcstnx_rd2xy PURPOSE: (one line) World Coordinate System transformation DESCRIPTION: given ra and dec in radians calculate x and y (in IDL coordinates - 1st pixel centered on 0) CATEGORY: Astrometry CALLING SEQUENCE: wcstnx_rd2xy, ra, dec, wcs, xout, yout INPUTS: ra - right ascention in radians dec - declination in radians wcs - a structure containing astrometric info (see hdr2wcs) OPTIONAL INPUT PARAMETERS: KEYWORD INPUT PARAMETERS: KEYWORD OUTPUT PARAMETERS: xiast, etaast - 'astrometric' xi, eta xip, etap - the non-linear xi,eta OUTPUTS: x, y - IDL coordinates - 1st pixel centered on 0 COMMON BLOCKS: SIDE EFFECTS: RESTRICTIONS: PROCEDURE: MODIFICATION HISTORY: Written 2006 Feb, by Leslie Young, SwRI
(See astrom/wcstnx_rd2xy.pro)