The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Dmitry Eliuseev:
Deep Sky Companion is a pocket encyclopedia on different objects in the outer space. With Deep Sky Companion, you can get information on the most popular space objects. Deep Sky Companion contains information on more than 100 popular and beautiful objects, such as star clusters, nebulae, and galaxies. On each object, you can get detailed information, its image and search map. All of these objects can be observed with an amateur telescope, the majority of the presented objects can be seen with binoculars, and the most interesting ones are visible with a naked eye. Deep Sky Companion also makes possible to quickly find a required object, searching by name, constellation, or tool used for observing the object.Deep Sky Companion is helpful for both studying astronomy and just relaxing under the starry sky.