Help to get 8km throw distance.

[Stk]

Hi, this is my first post on here :yh:
Goal: To throw a 532nm beam up to 8km, the beam should be clearly visible at the site of the dot (end site). I would like some guidance on laser power requirement and optics/beam expanders :yh:

 

[joeyss]

400mW of green should do it using a 10x beam expander , but I'm not quite sure about it. Ideally you could try using a telescope with a adjustable focus and adjust the beam to infinity. How important is the size of the dot to you? You never said.

 

[Stk]

Size of the dot should not be tiny or overly large, a couple of metres maximum.
Ive read a lot in the sticky and safety rules, safety first!

 

[joeyss]

Without a beam expander a laser with 1.4 mRad would have a beam size of 11 meters at 8 km away. It would be very faint in a dark environment.
With a 10 x beam expander a laser will have a divergence of 0.14 mRad and a dot size of 1.1 meters , which would be very noticeable in the environment.
400 may be overkill depending on what you're trying to do.
I'd recommend trying a 100mw first.
What are you trying to do?