Hi All,
The
12.5" f/4 Serrurier Truss Newtonian is now finished and up on the mount!
After some initial tests earlier this week I have been clouded out so thought I'd just post this quick test for fun: A single 5 minute sub of the Horsehead, taken with the new scope.
The only processing applied is a histogram stretch. Attached image is at 50% resolution.
At this stage there was still significant coma due to incorrect spacing between the Baader MPCC and the chip. It turns out the optimal spacing is slightly different when going from my old f/5 to the new f/4. I have since found the optimal spacing (added 1mm) so coma is now gone. Also visible is some vignetting in the right corners due to the secondary not being perfectly aligned under the focuser (fixed that yesterday).
I'm very happy with the performance of the Royce mirror. On the first night FWHM was consistently below 2" (lowest recorded was 1.37"), where usually I've had 2.5"-3.5" with the old 10" mirror. This horsehead was taken on the second night of testing and was the first long exposure I did. Seeing on that night was a little poorer with FWHM just above 2", but still better than what I'm used to.
I'm hoping for some clear skies soon to do more testing and to perfect collimation and spacing. I'm also getting an Ovision worm+block for the G-11 mount which should eliminate the egg-shaped stars that appeared in some of my later images. When taking the mount apart I actually found that one of the RA worm block bearings were not running smooth, so that's likely the culprit.
Regards,
Rolf
)
