[JohnH]

Ok, so I bit the bullet and decided to get rid of what I believed was tilt in my RC10 focuser...by adding the recommended tip/tilt plate. Here is the process I followed:

1. Installed the plate and adjusted the laser beam to hit the secondary dead center. Rotate laser to check for concenticity, all good.

2. Insert Cheshire - tweak the secondary to centre the reflection of the bright annulus and the secondary centre mark, all good.

Re-check the tilt, adjust and re-adjust secondary as required.

3. Check "hall of mirrors" for misalignment of primary (should be the only error left by now). Get everything concentric.

Re-check the tilt, adjust and re-check and adjust secondary as required.

Now I recon that was pretty good (see attached images), tighten up all and recheck....so now I just have to star test right? But this is where I struggle, visually a defocused star looks good but if I use CCDINspector on the image I get large and highly variable collimation errors reported. Is this bad seeing, tube currents or what? So far any adjustments I have made "under the stars" have made things worse not better.

So do I have to wait for a perfect night for the star test, (well good seeing and a full moon anyway)? I must admit I am uncertain how to differentiate between the various sorts of error by eye (and therefore which element to tweak - 1, 2 or tip?). Again, CCDINspector does the analysis but seems very prone to systematic error if the star field and tracking is not just so, it gives me a shot at separating collimation vs tilt error and curvature at least but again, to date, I have only made things worse and ended up back on the bench to get it back to not bad....grr.

So my question is - for that final tweak - what is the process you use?