tips please on how to check my focuser is in my refractor straight using a laser

[Piero]

I found this annotated image from this thread: 

https://www.cloudynights.com/topic/523392-replacement-focuser-for-sw-ed80/

It contains some good advice.

Could it be that your focuser misalignment was due to heavy load?

 

[Merlin66]

I have three ED80 and checked and re-aligned the focuser on each.

Just unscrew the three M4 screws which hold the focuser to the OTA, and gently nudge the focuser until the laser spot is central. Then re-tighten the screws while watching the laser spot.

works for me!