Technical Appraisal of New Visiting Instruments

Focal Length 45.7m (f/10.94). Unvignetted field diameter 15 arc minutes, 50% vignetting field diameter 19 arc minutes. Image Scale 4.51 arcsecs/mm.

Image quality: At nominal focus on a flat focal plane, less than or equal to 0.5 arcsec over a 10 arcmin field and less than or equal to 1 arcsec over a 20 arcmin field.

The Cassegrain Focal plane is 150 mm below the Interface flange of the Acquisition and Guidance box.

Instruments at CASSEGRAIN are normally mounted to the bottom Flange of  Acquisition and Guidance box. The interface flange is 1200 mm in diameter and can accept instruments up to an absolute maximum weight of 1500 kg e.g.  ISIS at Cassegrain. We can also accomadate lighter instrument  (80 kg to 400kg) but the mounting flange diameter is reduced to 660mm. This allows counter balance weights to be added to the larger diameter e.g. PNS at Cassegrain / ULTRACAM at Cassegrain. Instrument less than say 50 kg and a diameter of less than 300mm could use the auxiliary port on the Cassegrain Acquisition and Guidance box.

The rotator turntable on which instruments are mounted needs to be accurately balanced. Therefore instrument designs should incorporate mass symmetry with respect to the “on axis” turntable rotator centre.

The electronics controlling the instrument are mounted usually in one electronics rack hanging from the Cassegrain cable wrap. Visiting groups using their own rack must ensure their rack can be easily fitted and will support the weight required at all gravity vectors exposed to during normal operation. There is a maximum weight and a maximum size for the electronics rack. This needs to be discussed and agreed well before the observing run using the Technical Appraisal Form.

Focal Length 45.74m (f/10.94). Unvignetted field diameter 7 arc minutes, 50% vignetting field diameter 23 arc minutes. Image scale Scale 4.51 arcsec/mm.

Image quality : At the nominal focus on a flat focal plane, less than or equal to 0.5 arcsec over a 10 arcmin field and less than or equal to 1 arcsec over a 20 arcmin field.

Focal Plane is 585mm from the derotator turntable flange.

The GHRIL side turntable Flange can be used to mount small light instruments which can benefit from mechanical image rotation. The space envolpe for such instruments is tight because of the large optical bench mounted very close to the turntable flange. INTEGRAL at NASMYTH. The Nasmyth instrument rotator has two sets of mounting holes, 12equi-spaced M10 on a PCD of 362 mm and 12 equi-spaced M10 on a PCD of 457 mm. 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.

 

NASMYTH FOCAL STATION f/11 With optical image derotator

Focal Length 46.42m (f/11.11). Unvignetted field diameter 2.5 arc minutes, 50% vignetting field diameter 5 arc minutes. Image scale Scale 4.44 arcsec/mm.

Image quality : At nominal focus less than or equal to 0.5 arcsec over the 5 arcmin field.

Focal Plane is 585mm from the derotator turntable flange.

 

NASMYTH FOCAL STATION f/11 With UV/optical image derotator

Focal Length 46.42m (f/11.11). Unvignetted field diameter 0.5 arc minutes, 50% vignetting field diameter 2.4 arc minutes. Image scale Scale 4.44 arcsec/mm.

Image quality : At nominal focus less than or equal to 0.5 arcsec over the 5 arcmin field.

Focal Plane is 640mm from the derotator turntable flange.

 

NASMYTH FOCAL STATION f/11 With infrared image derotator

Focal Length 46.42m (f/11.11). Unvignetted field diameter 2.9 arc minutes. Image scale Scale 4.44 arcsec/mm.

Image quality : At nominal focus less than or equal to 0.5 arcsec over the 5 arcmin field.

Focal Plane is 451mm from the derotator turntable flange.

 

Ground based High Resolution Imaging Laboratory (GHRIL)

The GHRIL Enclosure is mounted on one of the NASMYTH platforms. It houses an optical table 2500mm long x 1350mm wide. Adjacent to the optical table is a small electronics room. The Optical axis is 150 mm above the optical table. The optical table is offset to the right of the incoming optical axis. The nominal optical axis is 425mm from the lefthand side of the bench. The distance from the optical bench to the derotator flange is 445mm.