ADC Review Approaches

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ADC ReviewApproaches

• J. Sebag

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Overview

• ADC used in telescopes
• ADC purpose
• ADCs currently in use
• Conclusion

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Types of ADC

• Rotating prisms (plano surfaces)
• Rotating Lens-Prisms, Lensm
• Linear prisms
• Decenter Tilt lens
• Liquid-filled prism (new technique)

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Rotating Prisms
KPNO 4m ADC Plano Prisms Diameter 280mm
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Rotating Prisms
MMT F/5 Wide Field Corrector ADC for
spectroscopic mode Plano Prisms Diameter 750mm
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Rotating Prisms
Magellan F/11 Wide Field Corrector ADC for
spectroscopic mode Plano Prisms Diameter
716mm (from Brashear)
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Rotating Lens-Prisms
Possible LSST ADC with 2 lens-prisms Diameter 1m
L3 Filt
L2
L1
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Linear ADC
KECK Telescope
Diameter 1m Length 1.7m
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Decenter-tilt lens
Subaru ADC in Suprime-Cam. The lens is moved
along the vertical direction Diameter 700mm
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Liquid-Filled ADC
The lenses rotate
Pan-Starrs design
Liquid-filled prism-shaped space between 2 flat
lens surfaces
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ADC Purpose

• High resolution imaging below 400nm
• Loss of efficiency in a spectrograph from
  chromatic dispersion (MOS)
• Observations at high airmass (gt2)

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Telescope ADCs
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Telescope ADCs
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Telescope ADCs
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Conclusions

• Results from 18 observatories
• 13 ADCs 4 linear, 4 Prism, 2 Lensm, 1 Liquid, 2
  Decenter
• 6 spectroscopic instruments ALL with ADC
• 12 imaging instruments 7 only with ADC
• Among the 7 systems with a FOV gt 1deg
• 3 without ADC (CFHT, SDSS, DEC)
• 1 with a removable ADC (VST)
• 2 with ADC (Pan-Starrs, DCT)
• 1 TBD (Vista)

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Conclusions

• Reasons given for NOT using an ADC
• Keep airmass lt 1.5
• Use narrow band filters
• No high-resolution imaging below 600nm
• Transmission loss
• ADC glass with low transmission in the near UV
  (removable near Zenith)
• More ghost images
• Seeing worst for high airmass in the blue/UV
• Added complexity and cost