The electronic download consists of a "starter" DVD-R ISO image (1)(2) and includes the MPOSC3 and APASS (DR-9, MPO format). The program also supports UCAC4 (native format) and CMC-15 (MPO format). The UCAC4, CMC-15, and APASS (DR-9) catalogs are available as 2 DVD±R dual-layer ISO images for free download(1)(2). Download instructions will be provided via email after receiving your order.(1) The ISO images must be burned to the approriate type of DVD disc before using. Software can also be used to "mount" the ISO images a drive on your computer. There are many programs available, one being Daemon Tools Lite, which is free (with advertising) or $5.99 for a no-advertising licence for 3 PCs. Windows 10 may not require the additional software and will see the ISO images a drive automatically. This must be confirmed before you decide whether or not to purchase image mounting software.(2) Connection and data rates may apply.Please NoteThe starter DVD is used to install all MPO programs. You will be provided with the necessary release code(s) to install only those products that you purchase.