not ANOTHER collimation issue

i must apologize in advance - i've read enough forums, talked to enough people, etc. to know more than i ever wnated to know about how to collimate my newtonion reflecting telescope. none of us need another question about collimation. i am, however, at my wits end to explain the following phenomenon:
my new orion xt8 came with a neat little collimation cap -a focuser dust cap with a shiny underside and a small hole in the middle. i later bought a laser. it's an antares single beam type.
i've practiced collimating with the cap so much, i enjoy it, and am lobbying for it to be an olympic sport in 2008.
so why, when i collimate my scope with my cap (the hole-in-the-dust-cap contraption), then check it with my brand-new single beam laser, does the beam hit 1.5" from the center of the primary?!
what is going on? focuser not square? secondary not concentric with focuser? collimator out of collimation? rift in space-time continuum?
i briefly checked that my laser was collimated. i quickly went through floyd's article (i told you i did my homework) and the beam doesn't move more than 1/8" at 10ish feet.
also - the star test (i've even been reading dick suiter's book) looks about right when i collimate with the cap, but i haven't looked yet with laser collimation.
assume, for the sake of argument, i went through the correct collimation procedure for both the laser and the cap.
scope is 203mm, 1200mm FL F5.91
thanks, nate

It's probably the little bit of play (slop) in the fit in the focuser. I've experienced the same thing with a Cheshire eyepiece when checking collimation versus the collimation cap.

Elliott
Orion XT8
Vista 10x50

Nathan,
the most likely problem is discussed in my article on laser collimator's. The 1.25" collimator's tend to be most problematic because of the 2" to 1.25" adapter having too much slop in the barrel of the focuser. Also combine the slop in the laser to the 1.25" adapter and you have a large deviation.
You can eliminate a lot of this by not using the set screw to hold th laser in the focuser. If there is any slop in the adapter to the focuser barrel then the same thing applies. Try checking with out tightening any of the screws in the focuser. If this does not help, then you must be getting the error with the other collimation device.
I would just use the laser and then see what the star test show.
Floyd

Thanks fellas.

i've got fellow astronerds here with glatters, kendricks, both barlowed and not. i'll try copmaring them with my cap.

sounds like i underestimated the role focuser->adapter->collimator slop can play in collimation.

of all the methods i've seen, the holographic projection to get everything 95%, followed by the barlowed laser is the most fun/easy/cool. it also requires the use of not one, but two lasers which means more dangerous radiation to play with. plus more equipment is always cool, in my book.

thanks again.