Help with DeepSkyStacker

[Starjumper]

Hi Guys,

I need your help, I am probably making a very basic error but this is the first time I have used this program.

I am trying to register and stack the following files:-

Light Frames 20

Dark Frames 1

Flat files 4

B,C,G & R Sigma files

all files are fits.

The error response I am getting is "The ckecked picture file are not compatibles ( Width,Height, number of colours,

number of channels, only one master dark, offset and flat )."

Tks

John