Motivation behind creating an app for photographing deep sky objects on a Mac
Currently, the use of CMOS cameras has become common in deep sky astronomy photography, and it has become standard to control everything from equatorial mounts to focusers and filter wheels all together on a computer. For Windows PCs, there is a system called ASCOM that acts as an intermediary between devices and apps, and there are apps that are compatible with ASCOM. Since Windows is a proprietary API, I think apps are made to take advantage of Windows' functions. (I have never used a Windows astronomy photography app, so I cannot say for sure.)