PCalc is a fully featured scientific calculator for macOS with support for hexadecimal, octal and binary calculations, as well as an optional RPN mode, parentheses, programmable functions, and an extensive set of unit conversions.
Using GrandTotal you can create invoices and estimates in the twinkling of an eye and keep track over the outstanding payments. Detailed statistics and graphs give you an insight into the current state of your business and allow comparison to previous periods.
Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope.