A .fit image is a raw file. Save your files as fit images(MaxIm) from Nebulosity. In DSS towards the botom on the left hand side should be a tab that can be set up like this
http://deepskystacker.wikispaces.com...ck+QHY8+images
except you will need to select your camera, not a QHY8(although, does the M25c use the same chip as a QHY8??). If it isnt there you could try the generec setting.
Then add your darks, lights, and flats or whatever you have and set your stacking parameters and it should spit out a colour image.
