Two-mirror telescope Calculator
Legend
- F/#
- System's effective focal ratio
- F₁/#
- Focal ratio of the primary mirror
- r₁
- Vertex radius of curvature of the primary mirror
- f₁
- Focal length of the primary mirror
- Dh
- Diameter of the hole in the primary mirror
- S₁
- Mirror separation (primary ↔ secondary)
- k₁
- Conic constant of the primary mirror
- k₂
- Conic constant of the secondary mirror
- r₂
- Radius of curvature of the secondary mirror
- f₂
- Focal length of the secondary mirror
- D₂
- Diameter of the secondary mirror
- Cc
- 3rd order coma coefficient
- Ac
- 3rd order astigmatism coefficient
- Cp
- Petzval field curvature
- Cm
- Median 3rd order field curvature
Equations
Median field curvature:
\(C_m = C_p - 4\,A_c\)