Schiefspieglers

Schiefspieglers are high F ratio tilted Cassegrain telescopes.  The High F ratio is needed to control both coma and astigmatism.  The most famous one is the Kutter 4.25 inch F/26.

$.25 Schief

4.25 Schief Telescope (1) 48×36 (B&W)

Larger aperture requires a higher F ratio still like this 6 inch F/32:

6 inch F32 DelmarvaSchiefbyDGroski.len

Higher F ratios means a very small field of view so a better way to make a faster Schief is to make the  secondary toroidal like this one:

8 inch F22.7 Toroidal Schief

But a toroid surface is not very easy to make so another option is to add lenses.  Buchroeder used one correcting lens but Dittie found that two lenses worked better:

6 inch F20 Dittie

12 inch F18 Dittie

Dittie vs Buchroeder Schief

Another way to deal with astigmatism is to add a weakly curved tertiary mirror called a Trischief.  Both Kutter and Buchroeder did this.  Here is one:

8 inch F19 Trischief

Schiefs are never as fast as a Chief and usually have a strongly tilted image compared to Yolos or Chiefs.