Summary of mechanical performance

• Telescope limits:

  Zenith distance < 70
  - 6 h < hour angle < + 6 h (above pole)
  Declination > -30 09 30
  

  Operation below the pole is possible, but only gains a small extra area of sky; consider it in exceptional circumstances.

  Note that the lower windshield causes vignetting for zenith distances > 57 and is raised for such observations.

  Figure shows the area of the sky normally accessible to the INT.

    
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  Figure: The area of sky accessible to the INT. Lines of equal zenith distance are drawn on a plot of declination against hour angle.
  

• Speed limits: Maximum speeds for hour angle and declination are 0.5 s and 1.3 s respectively.

• Tracking and pointing:

  Pointing accuracy: rms residual of a global fit = 5 arcsec
  Tracking accuracy:
  (unguided) < 1 arcsec in 3 minutes; < 2 arcsec in 10 minutes
  (guided) < 0.3 arcsec
  Offsetting accuracy: Less than 1 arcsecond using the AUTOFFSET command.

  
Table: Summary of mirror characteristics for the INT

  
Table: Optical characteristics of INT foci

  
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Figure: Spot diagrams for images at the f/15 Cassegrain focus of the INT, showing the dependence on field radius and the effects of defocussing.

  
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Figure: Spot diagrams for the prime focus of the INT with the three-element corrector at different wavelengths and field radii. The scale is shown by a circle of radius 1.0 arcsec.