Install saods9-doc by entering the following commands in the terminal:
sudo apt update sudo apt install saods9-doc
Description:
Image display tool for astronomy (help files/documentation)
SAOImage DS9 is an astronomical imaging and data visualization application. DS9 supports FITS images and binary tables, multiple frame buffers, region manipulation, and many scale algorithms and colormaps. It provides for easy communication with external analysis tasks and is highly configurable and extensible via XPA and SAMP. . This package contains the documentation and help pages.
Homepage: http://ds9.si.edu/
Version: 7.5+repack1-2
Section: universe/doc