They are just standard push pull screws Dave. I normally just use a
cheshire to check it. You can do it during the day, leave the dust cap on, put in the extensions for eyepiece use and use the cheshire. Turn the cheshire to catch the light and you'll see a black dot or two reflecting back. Adjust the screws to center the dot. It's much easier to see the dots on a bright day, just had a look through mine then and it's a bit dull today to see it clearly. I used to double check it with ccd inspector after dark, but it was always really close anyway.
Sure you don't have droop in the imaging train or similar causing the grief?