WHT f/11 Nasmyth focus

The drive side Nasmyth focus is occupied by the Utrecht Echelle Spectrograph. This has a dedicated A&G unit permanently mounted, thus access to this Nasmyth focus is limited. The GHRIL side Nasmyth focus can be used, although the positioning of the large optical table makes direct access to the Nasmyth turntable difficult.

• Mounting holes : The Nasmyth instrument rotators have two sets of mounting holes, 12 M10 on a 362 mm PCD and 12 M10 on a 457 mm PCD.

• Maximum mass and moments: The instrument rotators are designed for small lightweight instruments and are capable of supporting a maximum mass of 130 kg, a maximum moment of 65 kg m about the mounting face and a maximum out of balance moment about the axis of 10 kg m.

• Clearances and volumes: Access to the GHRIL-side Nasmyth turntable is restricted by the GHRIL table to a distance of 440 mm behind the rotator mounting face. The turntable mounting frame restricts the diameter to less than 560 mm. The optical axis is 150mm above the surface of the GHRIL table.