The ESA/ESO/NASA FITS Liberator 3 released late last year is now a stand alone application and does not require Photoshop.
FITS Liberator is free software that allows you to open astronomical FITS images, examine the header, make adjustments and even save the images as high quality TIFF files for manipulation in your favourite image editing software.
Earlier versions were provided as a ‘plugin’ for Photoshop. This latest release does not require Photoshop and can be used on its own to view and edit FITS files.
More information can be found at the ESA web site where the software can be downloaded at no charge.
Please note that together with RAW and calibrated FITS files, all images acquired by SPIRIT are still provided as high quality JPEG versions that do not require FITS Liberator, or any other specialised astronomical software in order to view and manipulate them. However, including FITS Liberator in your workflow will allow you to quickly access header information from the FITs versions, such as date, time, coordinate and exposure information, which is otherwise not possible using JPEG versions alone.
A guide on how to use FITS Liberator can be found here.