DESCRIPTION
XVista is a collection of programs that run on UNIX machines under X-windows
for the display and reduction of astronomical images. It has evolved from
PCVISTA (Treffers and Richmond, Pub. Astr. Soc. Pac. 101, pp. 725-730) which
was in turn designed to be a somewhat compatible subset of the VISTA program
developed at U.C. Santa Cruz and Berkeley for the reduction of CCD
data.
The C++ language source code can be found in ~treffers/XVista11.
Note: LOTS OF BUGS as documentation reflects older version
of the code.
IMAGE ARITHMETIC
- add -add images together
- sub -subtract images
- mul -multiply images
- div -divide images
DATA DISPLAY
- tv -display grey scale image on screen
- cursor -display data values at cursor position
- marks -display cross hairs on an image
- pfits -prints out image data on the screen
IMAGE STATISTICS
- abx - calculates miscellaneous statistics
- axes -calculates centroid of images
- hist -computes histograms
- mn -computes mean of images
- profile -makes a circular profile around a
centroid
- sky - computes sky (mode) level
PROCESSING
- bin -squashes an image
- clip -replaces pixels outside a specified
intensity range
- flip -changes orientation of image
- imshift -shifts image in rows and columns
- mash -generates spectra from image files into
ASCII file
- median -creates median frame from several images
- rotate -rotates images
- rowcol -cuts rows or columns from data into an
ASCII file
- smooth -convolves images
- window - cuts down images
HEADER MANIPULATION
- buffers -displays the FITS header variables
header
MISCELLANEOUS
- impatch -replaces pixel values in an image
- implant -inserts an image into another image
(montage)
- pstar - generates artificial star images
- xplot -plot program for columnar data
FOURIER ROUTINES
- fft1d - Fourier transforms columnar data
- fft2d - makes two dimensional FFTs of images
PHOTOMETRY
- stars -finds stars in an image
- phot - performs aperture photometry
DATA FORMAT
The image data are stored in disk files in
FITS
format, a commonly used
method of storing multi-dimensional data containing header information. A
description of the standard is given in Wells, Greisen, and Harten, Astron.
and Astrophys. Suppl. Ser, 44, 363
(1981).
The header contains information about the number of axes (always 2), the
numbers of rows and columns (NAXIS2 and NAXIS1 respectively) and the word
size.
Although FITS header variables such as the time and date of the observation
and the exposure time may be present, XVista makes little use of the header
data.
The header can be inspected by using the
buffers
command.
The data files usually have the four letter extension `.fits'. This extension
will often be added by XVista commands and need not be typed in explicitly.
You can read files with different extensions by typing them
explicitly.
Although internally most of the arithmetic is done as 32 bit floating point
variables, the
data are written as as 16 bit integers. The data are treated as
"signed" quantities ranging from +32767 to -32768.
The BZERO variable may be used to shift the origin but not
the range of the data.
On most commands the symbol '-' can be used in place of the
input and output filename and the file will be redirected
to stdin and stdout respectively.
In this way pipes can be used.
Last Revised October 12, 1999