FITS Preview 2.4 for Mac can be downloaded from our software library for free. The file size of the latest setup package available is 2.9 MB. FITS Preview for Mac lies within Design & Photo Tools, more precisely Viewers & Editors.
From the developer:
FITS Preview is a lightweight and fast viewer for images in FITS format (Flexible Image Transport System) introduced by NASA and HEASARC. The viewer is based on CFITSIO library and supports all standard monochromatic and color FITS image formats. The viewer can flip, rotate, debayer image (automatically if offsets fields in header are set correctly) and export images to JPEG format.
You may want to check out more Mac applications, such as Touch Bar Preview, Get Fit Stay Fit or Fitness Converter, which might be similar to FITS Preview.