The Yolo design is an unobstructed design using two concave tilted mirror. The resulting astigmatism need to be corrected by warping the secondary (into a toroid), correcting lenses or tertiary mirror.
A catadioptric Yolo design using 2 tilted correcting lenses
I’ve put the Chief correcting lenses in most telescope designs I could think of including the Yolo giving it the name “Jolo”. One of the difficulties of making a Yolo is the toroidal secondary mirror. Two correcting lenses can eliminate the need for a toroid or needing to warp the secondary. Surprisingly the two correcting lenses are tilted in the same direction unlike the Chief. This is because only astigmatism is being corrected. I still haven’t made one yet even though the spot diagrams are very good. Below is a design you can build or scale up.
A 12 inch Jolo
I found two lenses in the Ross Optics catalog that are large enough to use in a larger Jolo. I don’t know how expensive they are but the design is awesome across the visible range. It could even be scaled up twice as large if you could find the lenses.
The primary is hyperbolic but even so the aspheric deviation is only a fraction of a fringe. I still haven’t made one of these yet. Here is the Zemax data:
concerning toroid mirrors 081412Concerning Glass Bending
yolo_collimation_Beat_Eichenberger_english
JonesYolo_6_f15_final.len(OSLO)
A Yolo can also be corrected with a weakly curved tertiary as in the Solano:
Optical Ed's 