Hi Steve,
Use the BatchFormatConversion script (in Script->Batch Processing to convert the xisf files TIF or FIT files etc. See the attached screen shot. You just need to type in the file extension and the format you want (for example 16-bit integer or whatever).
Never be tempted to prevent Pixinsight working with the incredibly powerful xisf file format otherwise you will lose a lot of other functionality such as the History Explorer. Just convert at the last moment when you need another file format.
Cheers
Ian.
