ASIStudio 1.6.1 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The actual developer of this free Mac application is ZWO Company. We recommend checking the downloaded files with any free antivirus. ASIStudio for Mac lies within Education Tools, more precisely Science.
From the developer:
ASIStudio is a one-stop astrophotography software platform integrated with multiple standalone powerful software apps. With the clean interface and great interactive design, it is extremely easy to use and friendly to both beginners and advanced astrophotographers. It can automatically detect software updates to help you avoid the bother of downloading and updating manually.
You may want to check out more software for Mac, such as Trapcode Particular, Xfoil or DesignWorks Professional, which might be related to ASIStudio.