[bojan]

I think I should add two cents worth more to this discussion :-)
Many people are confused with these concepts...
There is a fundamental difference between "magnification" and "scale"..
"Magnification" is the factor by which the apparent angle of the object is magnified by the optical system, and it is approximatelly given by the ratio between focal lengths of objective and eyepiece.... This is non-dimensional number and is applicable to visual observations only, since only virtual images are dealt with (by "virtual" I mean the image of the object which size can not be measured in terms of length).
In case of any sort of projection on the sensor (film, CCD) (like prime focus image) the real image is involved and we are talking about "scale", which is expressed in deg/mm or arcsec/pixel... To calculate the approximate scale of the simple telescope-camera system we can use expression: s=0.057/FL where FL is effective focal length in mm. The result will be in degrees per mm and will be valid for only small angles (like up to 1 degree).
I hope this explanation will be helpful :-)