QLFits is the only OSX QuickLook for FITS files. It allows astronomers worldwide to quicklook their data right into the Finder, without having to open any application. It is for OSX 10.8 and up.
QLFits 3 is an entirely new implementation of QLFits, using the open-source projects ObjCFITSIO and AstroCocoaKit written by yours truly. QLFits show all HDU headers, and draw (when possible) all 2D images and 1D spectra.
QLFits reads the following extensions: fits, fit, fts, ft, mt, imfits, imfit, uvfits, uvfit, pha, rmf, arf, rsp, pi. If your FITS file is not recognised, let me know (cedric at onekilopars.ec), the dynamic OSX type of your file might not be included in the config of the plugin (which work with a combination of file extensions, UTIs – Universal Type Identifiers – and dynamic types...)
Install using Homebrew. Simply copy-paste the following command into a Terminal window:
brew cask install qlfits