Collimating a Newtonian

Hi guys, I am collimating my Vixen 4.5" f8. I venter spotted the primary and used a laser to align the secondary. Then I used a collimating tube and adjusted the primary till everything appeared to line up.

At very high power, here is the out of focus image I get. The shadow of the secondary seems respectably in the middle, but the bright diffraction rings are not totally circular but rather skewed on one side (looks like an oval but it not a perfect oval, rather think of a circle that is elongated on one half).

Any hints what I should be adjusting? Thanks a bunch!
Ivan

Attached Image:

Ivan: It looks like something is not quite right. (Duh) It could be a number of things. I generally don't have much luck with sighting tools, my eyes are just not up to it.

Since you have center spotted the primary,(hopefully with a donut)and you have a laser and presumably a barlow, I suggest aligning the primary using the "barlowed lazer" technique invented by Nils Olof Carlin.

Make a target for the barlow that has a hole in the center for the beam to pass through. Then simply insert the laser the barlow, the barlow in the focuser, turn on the laser. You should see the shadow of the center ring projected somewhere on the barlow target. Adjust the primary so the shadow is centered...

You may need a mirror to look up the focuser if your barlow is a shorty. That advantage of the barlowed laser is that it is insensitive to the rock and play in the focuser because you are looking at the reflection of a diffused beam.

Jon

Could one of the mirror clips be to tight?

FYI Dave H.