Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/ftp/software/tables/testdata/restore/sims/star_cluster/README Дата изменения: Wed Oct 6 20:08:45 1993 Дата индексирования: Mon Dec 24 01:04:05 2007 Кодировка: Поисковые слова: arp 220

This data set consists of simulations of a star cluster with a globular
cluster-like luminosity function (power) and spatial distribution (Hubble).
The range of magnitude is 6. The simulations have been computed for HST's
Wide Field Camera, CCD chip number 2, with both a spatially invariant PSF
and spatially variant PSFs. The simulated image is 256 x 256 pixels (of
the total 800 x 800 for the CCD) and is centered on the chip.

The file "star.lis" lists the coordinates and magnitudes for each star in the
simulated image. Two sets of position coordinates are given: (x,y) is the
position in the 256 x 256 simulated image, and (xwf2,ywf2) is the position
in WFPC chip 2. The column "pixval" gives the brightness of the star in DN.
There are 470 stars in the simulation.

The following parameters were used for the PSF computations (tinytim V2.3):

Instrument: 1 (Wide Field Camera) and 5 (WFPC/II Camera)
Chip: 2
Position on chip: xwf2 ywf2 (in star.lis)
Date of observation: 1 January 1993
Filter: none (monochromatic) or F555W
Wavelength in nm: 547 nm
B-V value: 3 (0.126, Type A)
PSF size in arcsec: 6.0
Subsampling factor: 1
Simulate jitter: No

Read-out noise and Poisson noise have been added to all images with prefix
sim (read-out noise = 13 electrons, gain (electrons/DN) = 7.5). Image
truth.fit is the delta-function source model with no noise. No background
was added to the simulated images sim1.fit, sim2.fit, sim3.fit and sim4.fit.
In sim5.fit a constant background of 10 has been added.

A set of PSF images is also included in this data set. The PSFs were simulated
in 5 x 5 grids across the central section of the chip, with size 256 x 256.
Positions of the PSFs on chipe are listed on file psf.lis. Image groups with
rootname mpsf and psf correspond to the monochromatic PSF and filter PSF,
respectively.

All data is stored in the FITS format as 16-bit scaled integers, and all data
files have the extension .fit.

> Update, 6 Oct 1993: The images sim1, sim2, sim3, sim4, sim5, and truth
were revised on this date to use volume-normalized PSFs rather than peak
intensity-normalized PSFs. The only difference for sim1 and sim2 is an
overall scale factor. The previous versions of sim3, sim4, and sim5 are
not really correct and should be discarded. The new truth image has a
range of DN such that, when convolved with the volume-normalized PSFs,
yields counts in the WFPC range of linearity (<4000). The table star.lis
contains not only the star positions and true DN values, but also the
corresponding true magnitude and two measured magnitudes (one from the
peak pixel value and one from aperture photometry). The zero point for
the magnitudes is 9.0. The maximum difference between the true magnitudes
and the measurements is 0.01 mag. < End update.

Files
-----
star.lis star list
psf.lis PSF parameters

truth 470 point sources (delta functions), no noise, no background

sim1 WF, space invar PSF (mpsf12.fit), mono, center of image
sim2 WF, space invar PSF (psf12.fit), F555W filter, center of image
sim3 WF, space var PSF, monochromatic
sim4 WF, space var PSF, F555W filter
sim5 WF, space var PSF, F555W filter, background=10.0

sim1c WF2, space invar PSF (mpsfc12.fit), mono, center of image
sim2c WF2, space invar PSF (psfc12.fit), F555W filter, center of image
sim3c WF2, space var PSF, monochromatic
sim4c WF2, space var PSF, F555W filter
sim5c WF2, space var PSF, F555W filter, background=10.0

mpsf(00-24) 25 WF PSFs, monochromatic
psf(00-24) 25 WF PSFs, F555W filter

mpsfc(00-24) 25 WF2 PSFs, monochromatic
psfc(00-24) 25 WF2 PSFs, F555W filter

Stars.tar.Z All of above files in compressed tar format.