Hi,
This might help:
System Parameters
Pixel Scale form nova.astronomy.net
Canon 600d - 1.42
ISO Gain RN DC*
-----------------------------------------------------------
100 8.79 15.5 0.146
200 4.40 8.1 0.081
400 2.19 4.8 0.048
800 1.12 3.2 0.039
1600 0.58 2.5 0.036
3200 0.29 2.2 0.041
6400** 0.15 2.1 0.039
12800** 0.07 1.9 0.035
--------------------------------------------------------
Gain = conversion factor, electrons per ADU
RN = readout noise, electrons r.m.s
DC* = electrons per pixel per second (bogus value, see below)
** ISOs 6400 & 12800 are in fact digitally stretched ISO 3200
I don't normally worry about these setting as I just use the defaults, because all the images have the same ISO/Exposure/F stop.
Look up
John