Is it necessary to use a centre spot on the primary when laser collimating ?
Not experienced in newtonian OTA assembly and initial collimation , my thoughts are that if the laser retraces it's own path perfectly back to laser emitter (which is in the focusor) then that's sufficient proof that the secondary and primary are properly aligned , centred and collimated.
Else the laser will not retrace it's own path ??!!??
Thoughts anyone ....