Hardware Overview
The Nickel telescope's Ritchey-Chretien optics utilize an f/5.3 primary mirror of 38.5" diameter and a secondary providing an f/17 cassegrain focus -- the telescope's sole focus -- with an approximate scale of 12.25 arcsec/mm. About 12% of the light is blocked by the secondary.An f/17.5 chopping secondary may be mounted for IR work. Observers should consult with a support astronomer if they wish to use the chopping secondary before applying for observing time.
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The telescope and dome are fully computer
controlled, though manual control of most systems is also possible
(refer to Figure 1 for locations of the telescope slew paddle,
secondary focus paddle, dome rotation rocker switch, mirror cover
open/close switches, and flat field lamp controls). The rainscreen (see Figure 3) and the ventilation
fan shutters are the only items in the Nickel dome not yet remotely
operable.
To move the telescope it is necessary to enable motion (e.g. turn on the telescope power) with the Telescope Motion Enable Switch (see Figure 1). Before moving the telescope, make sure that all ladders, equipment, or other obstructions have been moved away from the telescope. There is a Local Observer Button (see Figure 5) located in the electronics rack that also holds the flat-field lamp power supply that local observers should push to indicate that they are present. When the button is pressed the LED beside it will flash three times to indicate that the button-press has been recognized. The observer type field in the Naux_fe will also be set to "Local Observer", allowing you to open the dome (weather permitting, of course). The LEDs on the panel may be turned off to prevent stray light from getting into the telescope. There are three ventilation fans in the Nickel Dome. These ventilation fans have shutters which are normally closed during the day. These shutters should be opened before turning on the vans. Also, if the humidity is above 80%, you should not use the ventilation fans. Below the primary mirror is the Telescope Utility Bin (TUB) (see Figure 2) which contains the diagonal mirror, arc calibration lamps, and the guide camera. While it is possible to rotate the TUB (and hence the instrument), this can only be done with advance consultation with Observatory staff and to only a fixed position for the full night. The science instrument is mounted below the TUB at the cassegrain focus. Most instruments hang from a mounting triangle, though it is possible to mount large instruments to the TUB directly. If providing your own instrument, consult with staff members about how to best mount your instrument before applying for telescope time. An aperture and filter wheel assembly (see Figure 2) is available when using the mounting triangle. If using one of the two facility instruments for the Nickel telescope, the Nickel Direct Imaging Camera or the Nickel Spectrograph, this unit will be installed by default. Included in the aperture and filter wheel assembly is a 4 inch diameter iris shutter. This shutter is used with the Nickel Direct Imaging Camera and Nickel Spectrograph and is available for use with visiting instruments with advance consultation with the Observatory staff. Exposures of less than 1 second are discouraged with this shutter because of shutter timing errors and uneven illumination of the field (though it should be less than 1% for a 1 second exposure).
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Figure 1: Manual Controls in Nickel Dome
Figure 2: Equipment on Nickel Telescope
Figure 3: Equipment on Nickel Telescope
Figure 4: Flat Field and Wind Screens
Figure 5: Local Observer Button Panel |
