The solution is to attach the laser every time the same way, even if it’s tilted. At least it’s tilted every time the same amount. Most likely later the attached DSLR will also be slightly tilted the same way due to its weight. Probably not the best solution, but so far it works for me.
So, I attach the laser collimator to the focuser while the telescope lies in the same position that I attach the DSLR. Additional I simulate the weight of my 70D by pulling down the collimator a bit and then tightening the 2″ to 1.25″ Twist-Lock adapter.
Maybe a weight similar to the 70D to hang from the laser would be great to keep the tilt level the same for each collimation.
For the collimation, I mount the 130PDS on my GEM28 and position it as if I were photographing an object in the night sky. The scope is then at about a 45° angle, what is recommended in many collimation guides I’ve read.
After that, when I disassemble everything and reassemble the same way, the collimation still looks the same as before 🙂 !
That was never the case when I wasn’t paying attention to the laser attachment. It tilted a little differently each collimation… so I had to readjust my 130PDS with every single time, even if it was done twice in a row.