Welcome to the fifteenth version of XVista, codenamed "xvista-0.1.16" (dated May 10, 2020). XVista is a suite of programs for analyzing and displaying astronomical images on computers running Unix-like operating systems and X Windows. The code is written in ANSI C, and much of it doesn't make any graphics calls, so you can use parts of it even on systems that don't have X Windows. XVista is designed specifically for reducing large amounts of imaging data automatically; therefore, it doesn't have much of a user interface, and it isn't friendly. If you like GUIs, you won't like XVista. Everything is done from the command line, with a plethora of command-line options. It can be unpleasant. On the other hand, if you are trying to put together a set of arithmetical operations to be applied in sequence to several hundred images, it may be just what you want. XVista was (and is) written by Richard Treffers, at the University of California, Berkeley Michael Richmond, at the Rochester Institute of Technology It was inspired by a program called "Vista", which was written by Richard Stover and Todd Lauer at Lick Observatory [1]. We created a set of programs that looked similar, but ran individually (rather than inside a single process) and was designed to work on PCs with only 256 K of memory. The result was PC-Vista [2]. Over the years, we ported the program to the Unix environment (which wasn't so hard) and X Windows (which was). We have used it to acquire, display, and reduce the data taken by a series of automatic telescopes at UC Berkeley and (recently) Lick Observatory. See, for example, our article on BAIT [3], or papers based on BAIT data [4,5]. This is the twelfth time I've tried to bundle all the XVista code into a single unit and give it to other people. I'm sure that I've made a number of mistakes. Please read the notes at the start of the INSTALL file before you try to use any of the programs. If you do use the code, and find bugs, please tell me. I'll even consider adding options or new features, although I don't promise to do that. The first thing you should do, after reading this file, and unpacking the source code, is to read INSTALL, and then "xvista.1" file in the "man1" directory. That explains the basic usage of XVista commands. It might even help to read the PC-Vista paper [2], although it's seriously out of date in some ways. You might also look at a tutorial I have written for students in one of my classes. The XVista Tutorial is at http://spiff.rit.edu/classes/phys445/lectures/tutorial/tutorial.html and may grow with time. It should help you to see what sort of a package XVista is, and whether it might meet your needs. Any constructive comments and suggestions are welcome. Please let me know if you find XVista useful. Michael Richmond May 10, 2020 References: [1] Stover, R. J. 1988, in "Instrumentation for Ground-Based Optical Astronomy", ed. L. B. Robinson (New York: Springer-Verlag), p. 443. [2] Treffers, R. R. and Richmond, M. W. 1989, Publications of the Astronomical Society of the Pacific, 101, 725. [3] Richmond, M. W., Treffers, R. R. and Filippenko, A. V. 1993, Publications of the Astronomical Society of the Pacific, 105, 1164. [4] Richmond, M. W. et al. 1994, Astronomical Journal, 107, 1022. [5] Richmond, M. W. et al. 1995, Astronomical Journal, 109, 2121.