[SkySearcher (Daniel)]

Hi Guys

I have been having some issues trying to collimate my 12" GSO dob. I have had it for about 8months now and have been trying with varying degrees of success to get it collimated. I had never looked through such a scope prior to my purchase which doesn't help the situation much. I have constructed a basic tool using a film canister with a 1.5mm hole drilled in the exact centre of one end. I then painted a very small circle around the inside of the small hole and am able to illuminate it using an LED attached to another small hole on the side.

I can easily line up the primary centre spot with this small hole in the filem canister and can do a star alignment accurately using a magnifications upto 333x.

However, my question is, how do I know the secondary is lined up and will a star test show an incorrectly collimated secondary?
When looking through the film canister there are many positions the secondary can be in and still show the full primary reflection and of course I can then adjust the primary to place the centre spot directly in the centre of the draw tube.

I lined it all up and looked at 47tuc. At 15mm it was just ok but at 9mm it was a blurry blob with barely any resolution. The start test still shows a 'perfect' donut.

I just have the standard eyepieces supplied with the Scope, but I'm sure it can do better.

Any ideas?

Thanks in advance