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.

We also have alphabetic listing.

IMAGE ARITHMETIC

DATA DISPLAY

IMAGE STATISTICS

PROCESSING

HEADER MANIPULATION

MISCELLANEOUS

FOURIER AND SAMPLING ROUTINES

STAR FINDING AND PHOTOMETRY

ASTROMETRY

ADDITIONAL KEYWORDS

Many of the commands have unlisted keywords:

BOX SPECIFICATION

Many commands limit their effect over a region of the image. These regions are defined using the box= keyword where there value has the following format: 
box=sr,sc,nr,nc
box=cr,cc,nr,nc,1
Where sr and sc are the starting row and starting column, nr anr and nc are the number of rows and columns and cr and cc are the center row and center columns. Note the use of extra field (,1) that tells whether the starting or center positions are used.

STAR FORMAT

Starlists are used by several programs. They have a rather evolving format similar to 
row=    col=   peak=  fwhm=  back= ellipse= name=
The row and columns are in pixel coordinates (1 based liked FITs), the peak_height might be peak_totals in ADUs. Lines prefaced with the '#' sign are ignored.

As second World format is 

ra=ra(hh:mm:ss) dec=dec(dd:mm:ss) equinox_year  mag=magnitude  name=name
is also used.

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 header 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. The extension can be overwritten, by setting the environment variable FITS_EXTENSION.

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.

Internally the data are indexed with the C convention of 0 based indexes, but whenever they are output to the outside world they are converted to the FITS standard 1 based index. This is a very dangerous procedure and has hopefully been done correctly.

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.

BUILDING AND INSTALLATION

The code uses public domain code and requires some special programs and libraries. For Ubuntu 
cfitsio-dev
libcfitsio-dev
libgd-dev
libwcs7-dev
wcslib-dev
libgsl-dev
In addition the TELESCOPE environment variable should be set to tell the name of the user to which the programs will be installed. All the executables will be copied into ~($TELESCOPE)/bin when the make install is executed. Finally there are some miscellaneous programs that are needed by stars. These can be provided upon request:
Calling index