NTT Technical Characteristics

Location
Location 70° 43'54.272" W  -29° 15'18.440" S
Altitude 2375 m.
 Optical Design Ritchey-Chretien
Main Mirror Schott Zerodur
Diameter 3.58m, thin meniscus (24cm), 
Active Optics 75 actuators, 3 fixed points, 24 lateral actuators
Focal Ratio f/2.2
Secondary Mirror Schott Zerodur
Diameter 0.875m
Central Obstruction 1.16m
Tertiary Mirror Schott Zerodur
Major x minor axis 0.840 x 0.600m
Nasmyth foci
Field of view 30arcmin, 336.6mm
Focal Ratio f/11
Plate scale 5.35905 arcsec/mm
Image Quality 80% energy in 0.15" in all telescope position

General Lens Data (w/o adapter and instruments)

Surfaces 10
Stop 5
System Aperture Entrance Pupil Diameter = 3500
Glass Catalogs schott MISC
Ray Aiming Off
Apodization Uniform, factor = 8.00000E+000
Effective Focal Length 38501.74 (in air at system temperature and pressure)
Effective Focal Length 38501.74 (in image space)
Back Focal Length 21267.2
Total Track 6500
Image Space F/# 11.0005
Paraxial Working F/# 11.0005
Working F/# 11.00618
Image Space NA 0.04540561
Object Space NA 1.749999e-007
Stop Radius 1750
Paraxial Image Height 0
Paraxial Magnification 0
Entrance Pupil Diameter 3500
Entrance Pupil Position 6500
Exit Pupil Diameter 949.3438
Exit Pupil Position (before image plane) 10443.25
M1-M2 distance 5933.3
M1-M3 distance 1200
M3-focus distance 4100.6
Radius of curvature in the image plane 1898
Field Type Angle in degrees
Maximum Field 0
Primary Wave 0.55
Lens Units Millimeters
Angular Magnification 0

Surface Data Summary

Surf Type Comment Radius Thickness Glass Diameter Conic
OBJ STANDARD Infinity Infinity 0 0
1 COORDBRK - 500 - -
2 STANDARD SPIDER Infinity 0 3500 0
3 COORDBRK - 0 - -
4 STANDARD Infinity 6000 3500 0
STO STANDARD M1 -15400 -5933.3 MIRROR 3500 -1
6 STANDARD M2 -4416.7 4733.3 MIRROR 805.1247 -2.249926
7 COORDBRK - 0 - -
8 STANDARD M3 Infinity 0 MIRROR 552.5702 0
9 COORDBRK - -4100.6 - -
IMA STANDARD Infinity 0.0001346372 0

General Characteristics of the Rotator

Angle of rotation +/- 270 degrees
Maximum speed 2 tr/min
Maximum acceleration 0.3 degrees/sq s.
Maximum rotation speed 0.3 degrees/min
Acceptable imbalance for instrument 40 Nm
Safety brake 1500 Nm
Inertia without instrument 400 Kg*(sq.m)
Inertia with 2 tons of Instrument (EMMI) 2300 Kg*(sq.m)

Mechanical Characteristics of the Rotator

Drive one direct brushless cooled torque motor from ETEL
Outer diameter 770 mm
Inner diameter 556 mm
Thickness 98 mm
Peak torque 530 Nm
Running torque 300 Nm
Water flow 6 l/min
Inlet temperature 2 to 3 degrees below ambient temperature
Temperature gradient 1.5 degrees

Electric Characteristics of the Rotator

Electrical time constant 6.2 ms
DC resistance 37 ohm
Torque sensitivity 132 Nm/A
Back EMF 167 V/rad/s
Power input at stalled torque 350 W
Supply voltage 400 V (maximum)

Encoder

Heidenhain absolute encoder identical to the telescope
32768 reference circle with hub
2 scanning units
2 AWE 1024.700 analysis electronics
1 power unit NG100

Bearing

Pre-stressed double race ball bearing from RKS with the following characteristics:
Outer diameter 1728 mm
Inner diameter 1480 mm
Thickness 90 mm
Pre-stress 30 micrometers
Lubricator SKF LGLT2 or AEROSHELL 16
Friction about 100 Nm
Torque on bolts inner ring 25 Nm
Torque on bolts outer ring 35 Nm

Safety brake

From ATV, electromagnetic with spring type 450 SE, with power supply ESE 1000
Brake torque 3000 Nm
Power supply 220/380 V
Max. power 1000 W
Continuous power 44 W

Interface with the Instrument

Back focal distance 500 mm
Focalisation possibility +/- 10 mm
Lateral displacement at the focal plane for max. load on adapter 6.2 microns
Max. allowable tilt of the hub 3" for a load of 800N at 400 mm from the fixation flange
Flange outer diameter = 1630 mm
48 holes M10, depth 12 mm on dia.1580 mm
internal diameter = 1520 H7, depth 6 mm
Max. load conditions A) 2000 Kg between the flange and the focus (270 mm from the fixation flange)
B) 12000 Nm after the focus
Max. axial runout under load conditions 35 micrometers
Radial runout under load conditions 35 micrometers
 
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