Quote:
Originally Posted by mldee
Based on your results, there certainly doesn't seem to be much need for an OCAL with the Mewlon,
As there is only the secondary mirror adjustment on the Mewlon, it would appear to be quite sensitive relative to the small change in the before and after OCAL pics.
I notice that there is also very little OCAL ring offset needed, just -1H on pic2. I was needing 6 before then -14 after adjustment on the Newt.
My eyesight has let me down with the TC tool, I'm looking forward to my star tests if the rain stops. 60mm today.  |
I think that the Mewlon’s have an elliptic primary mirror with a spherical secondary mirror. The collimations screws are so tight I tend to go by how they "groan" rather than say, 1/30th turn.
I suspect that with a spherical secondary, any adjustments made to the secondary collimation screws may still produce an acceptable pattern to appear in the OCAL view, but may lead to the optical axis of the secondary becoming misaligned with the primary mirror axis. This might be why I got the poor star test.
As for the Tak Collimating Telescope, there are so many circles and also, I notice that the “X” formed by my spider vanes is offset from the centre, but the scope still produces sharp views and images, so I’ll stick with the star test.
Cheers
Dennis