4 vane spider alignment

How do I align my four vane spider on my Orion XT12I?
What is the best way to check the Mechanical and Optical alignments.
I am very frustrated because star clusters and such are clear, but major planets just can't come to a crisp focus.
HELP!!

I am not sure why you are trying to align the spider. But, the spider should be centered in the tube, the length of each to the inside wall from the center of the stud should be the same. The vanes should be straight and vertical so they give the thinest profile.
But is sounds like you are experiencing another problem. Are you collimating the scope?

It is highly unlikely that spider alignment is your problem. Collimation is more probable. But, many things can affect the view. For example, the other night I noticed a significant variation it the focus within the FOV only to realize that I had not tightened the set screw in the 1.25-2.0" adapter. Thus, the EP was setting slightly askew in the light path.

All of the Orion XT and XTi scopes I have seen have good to excellent optics and were easily collimated.

Also, keep in mind that using a laser to collimate may be causing some problems. One way to demonstrate
this is to rotate the laser in the focusser and watch the spot position on the primary. In my case the laser traced a circle meaning that precision with a laser was not achievable since the adapter had too much play in it. And it wasn't the laser's fault because when checked for alignment the laser remained rock steady at 30' when rotated in a controlled test.

It may take a while to understand the vagaries of collimation and the impact they have on your particular scope. But the effort is worthwhile for the views you can achieve. After significant efforts in the past it now usually takes less than 30 seconds to collimate my scope.

Active cooling, across the face of the primary if possible, can also help.