Posted By Robert Howe
I am trying out a used TV 76. My TV 85 and 102 and Genesis all had perfect point stars across the entire field, so this is the performance that I expect of the 76.
Last night, the 76 showed comets everywhere peripherally, which came to focus--but then the center was out of focus. There was an area (lower left as one sights through the scope) in which no star would focus, they were either wide or double as I focussed in and out.
I used AP and Televue diagonals; EPs included TV 35, 24 and 19 Panoptics; 22, 13 and 9 Naglers; 13 and 8 Ethos. Only the 9 mm Nagler, with the smallest FOV, showed no aberrations; the 8 mm Ethos showed less than any of the others. But the entire FOV of the 9 Nagler would be the central image of the 22 Nagler.
Looking at the moon with a 19 Panoptic, one limb would be clear and the opposite, out of focus.
A star test showed the enlarged image to be considerably out of round. The telescope was well equilibrated when I observed and my TV85 worked perfectly as did a Tak 60.