Yet Another Collimation Question

[astromerlin]

Hi all, Well it's been a while now since first collimating my SW250.

I spent a lot of time over it and with an SPC900 at prime focus

I have got it spot on. However, I have been trying to image DSO's

at a reasonable FOV and bought a GSO 0.5 reducer to try out.

It took ages to get the CCD distance right and I trimmed off some

of the webcam adapter in a lathe to achieve the right distance.

I finally got it to focus but I noticed that when pointed at a bright

star, either side of focus the center shadow is off to the lower

right on my screen. I think i'm right in assuming that due to the

change in the focal point it is showing that the collimation is not

right somehow.

Does anyone have some ideas to how to correct this, I'm having nightmares

thinking about continually swapping from prime focus to the 0.5 reducer whilst

tweeking the focuser/secondary/primary.

Edit: I forgot to mention that with the reducer in I'm getting elongated stars

horizontally even when I try 30sec subs.