This calcaulator will help you calcaulate the magnification of a laser beam by a telescope consisting of two convex lenses
$M'$=$M\sqrt{1+(\frac{\lambda l}{\pi W^2_0}})^2$ $M$=$\frac{F_2}{F_1}$
Laser Wavelength $\lambda$; Focal Length of Lens (input side) $F_1$; Focal Length of Lens (output side) $F_2$; Incident laser wasit radius $W_0$;
Distance between the input waist and the input lens $l$;