In contrast to RC and CAT designs, refractors appear to have a problem with very long imaging trains, incorporating:
a. A/O assembly
b filter wheel
c camera
d OAG or VanSlyke slider
The sticking point is the requirement for the field flattener to be placed at a very precise distance from the image plane. It can't simply be placed at the front of the imaging train, and these flattener cells typically have threading special to the telescope.
I've been looking at the very newest Petzval derived refractor designs, hoping that one would present a solution. Petzval designs have a flatter field to begin with, possibly negating the need for a flattener. However, in consultation with one importer, the field for his design is acceptably flat up to about 14mm, when a flattener is not used. This precludes the use of the new, large sensors.
I would be very interested to hear of solutions I have overlooked.
a. A/O assembly
b filter wheel
c camera
d OAG or VanSlyke slider
The sticking point is the requirement for the field flattener to be placed at a very precise distance from the image plane. It can't simply be placed at the front of the imaging train, and these flattener cells typically have threading special to the telescope.
I've been looking at the very newest Petzval derived refractor designs, hoping that one would present a solution. Petzval designs have a flatter field to begin with, possibly negating the need for a flattener. However, in consultation with one importer, the field for his design is acceptably flat up to about 14mm, when a flattener is not used. This precludes the use of the new, large sensors.
I would be very interested to hear of solutions I have overlooked.
