APN image green - by: rmor51

I capture last day M13 with a Canon 450D and Ekos. The image on the screen, into the FIST Viewer, was green. Curiously the FITS image downloaded is black and white, with very little signal . In fact I can see anything and I have to improve the signal with Photoshop in order M13 appears.

So why green ?
And why such difference between the fits viewer and the fits image ?

Thank you for your support.