When an error prevents CFITSIO to open the FITS file, the error message of its status is brought up to the user level, for an easier debugging.
As usual, to install or re-install the latest version of QLFits3, use the one-line installer:
curl -fsSLk https://raw.github.com/onekiloparsec/QLFits/master/Scripts/install.sh | sh
QLFits is certainly the most well known of of my software. It all started just before iObserve, actually, back in 2010! Long ago, when QLFits was in version 2.0 (or even before, I think), there was the possibility to customise the output. This is a requested feature again. And indeed, some people want to customise the output, not really the look of it, but rather the presence, or not, of the headers, by defaults.
Given the very small amount of documentation that Apple is providing on that matter, I am struggling a bit alone. However, I got help from the developer of another great QuickLook plugin: BetterZipQL. You must definitely grab it. It’s free, and provide invaluable insight of your zipped files.