hi again Fernando
agree with James - the GSO primary mirror mounts definitely need tightening up. Even with a stiffened up mounting, things move around so much that you will always need to touch up the collimation using a star near to the target object if you want to get the best possible resolution for planetary imaging.
Re the offset of the shadow pattern, if you have any small offsets in the (focuser/centre spot/secondary in-out), the action of doing a collimation will push the input light column off the tube axis as you adjust the primary to compensate - the mirror does not move sideways, it just points away from the tube axis a little and you get the sideways offset that you see in the shadow picture. A little bit of offset doesn't matter for planetary imaging and the result you posted does not show any really bad mechanical misalignment, so suggest you put that on the back burner for now and refine the collimation as James indicates. You should be able to get good planetary images with it as it is set up and if it produces really bad star tests, it is not due to the mechanical alignment that you have shown. Maybe fine tune the alignment later on if you feel the need, but it really does look good enough to work OK.
"It is amazing how everything looks different when I check the collimation using a Cheshire."
then rely on the Cheshire - which shows the optical alignment. The shadow projection technique is primarily designed to show mechanical alignment after collimation and it only indirectly indicates some aspects of optical alignment - it quickly shows if anything is grossly out of alignment but still collimatable.
However, your description of the star test problem sounds like strong tube currents. Did it look like example 8 in figure 96 of?:
http://www.telescope-optics.net/diff...berrations.htm
or the example in
http://www.backyardastronomy.com/Bac...0A-Testing.pdf
Could there have been a large temperature difference between the scope and the air? My 12 inch scope needs an hour or two with the fan on to stabilise if it is a long way off ambient temp.
regards ray