Rob,
I can't fix your guiding but this might take care of your vignetting.
I found any sort of flats fixed my images a lot, so, something to do on a rainy day, with about $40 in bits for my scope, probably 1/2 that for yours, make a light box.
The box is foam board from office works (comes in 770x500 sheets for $12), plexiglass from a glasier in moss street (255x255 was $10, cut while you wait) plus 4 white LEDs, a limiting resistor and power socket from dick smiths (Under $10) and a link to work out LED limiting resistors (priceless).
http://www.quickar.com/noqbestledcalc.htm
Hot glue gun, box cutter, ruler and I used black silicon to light seal the joints at the end although gaffa tape may have been neater. I have it so it plugs into the mounts 12v supply. You could easily make different sized entry plugins for different scopes. It simply pushes onto the end of the scope, it's pretty light.
Mine has a 220mm opening and is 200mm deep. I've since read that the depth only needs to be 70% of the opening but I just planned mine around 2 foam boards cos that is what I bought
No photos using it yet, I don't have my astro camera at the moment, so I'm not sure if using white LEDs is the way to go or not. However they only have a 15 degree light spead so I didn't need any internal baffling to keep direct light off the diffuser. I simply bent and hot glued their legs, pointing the lens to the back/top of the box.
It's based on ->
http://www.gregpyros.com/html/light_box.html His uses drafting mylar as an initial diffuser internally but I went to a drafting supplies shop and that stuff is obselete. They could get it from the vault in Sydney, but not one sheet. They
gave me some drafting tracing paper which looks the same optically, but it would tear if stressed. I didn't bother using it as I didn't use normal light bulbs.
I'm hoping I can use it to set a custom white balance to sort out that Astronomiks CLS filter I bought and to be honest, any flat is better than none.
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