MDM Observatory's 8K CCD array project:
OPTICAL PARAMETERS OF HILTNER 2.4-METER TELESCOPE e-mail:
arlin@astro.columbia.eduTelephone: (212) 854-7899 |

Fundamental parameters are in **bold** text, other parameters are derived.

PARAMETER | IN INCHES | MILLIMETERS | Comments |

f/2.07 PRIMARY MIRROR | |||

Diameter of front face | 93.0 | 2362 | |

Clear aperture (after masking) | 91.5 | 2324 | |

Thickness | 9.2 | 234 | |

Diameter of central perforation | 12.0 | 305 | |

Weight | 4400 lb | 2000 kg | |

Paraxial radius of curvature | 379.24 | 9632.7 | |

Sagitta | 2.86 | 72.6 | |

Conical constant (dimensionless) | -1.05015 | E&F'97 use -1.050145 | |

f/7.5 SECONDARY MIRROR | |||

Diameter of front face | 26.625 | 676.3 | |

Illuminated diameter of front face | 26.0 | 660 | |

Secondary baffle outside diameter | 29.25 | 743 | |

Thickness | 3.125 | 79.4 | |

Paraxial radius of curvature | 130.263 | 3308.7 | E&F'97 use 3308.68 mm |

Conical constant (dimensionless) | -3.54396 | ||

Prime focus intercept | 47.64 | 1210 | |

Vertex separation of mirrors | 141.98 | 3606.3 | E&F'97 use 3608.98 mm |

Back focal distance (mechanical) | 35.4 | 899 | |

Back focal distance (optical) | 35.21 | 894.3 | |

Back focal range (optical) | +0.35 to -0.25 | +8.9 to -6.3 | |

Final focal ratio | f/7.31 | from E&F'97 | |

Paraxial image scale | 0.0864 | in mm/arcsec, from E&F'97 | |

Inverse image scale | 11.50+-0.005 | in arcseconds/mm | |

Focal surface curvature radius | 49.64 | 1261 | from E&F'97 |

Unvignetted field diameter | 4.9 | 125 | value in Manual |

Unvignetted field diameter | 7.2 | 182 | calculated value |

The unvignetted field diameter calculated from the diameter of central perforation, the f-ratio and the back focal distance is 182 mm. The baffle behind the primary is somewhat over 11 inches in diameter, near the front surface of the primary (according to Bob Barr, 25 Nov. 1998), which would produce an unvignetted field diameter of about 6.3 inches, or 160 mm. The value in the Manual by Mack et al. appears to be the limit imposed by the entrance aperture of the old MIS.

Note that the Mack et al. and E&F values for the image scale differ by 0.6%.