Abstract
Atmospheric dispersion produces spectral elongation in images formed by land-based astronomical telescopes, and this elongation increases as the telescope points away from the zenith. Atmospheric Dispersion Correctors (ADCs) produce compensating dispersion that can be adjusted to best cancel out the atmospheric effect. These correctors are generally of two basic types: Rotating Atmospheric Dispersion Correctors (R-ADCs), and Linear Atmospheric Dispersion Correctors (L-ADCs). Lately, a third type, the “Compensating Lateral ADC” (CL-ADC) has been proposed. None of these design approaches allow for large corrector systems (with elements greater than 1 m in diameter), in which the secondary spectrum is corrected to small residuals, of the order of tens’ of milliarcseconds. This paper describes a new type of large corrector (>1 m diameter elements), which can achieve the correction of the secondary spectrum to the order of 10 milliarcseconds. This correction is achieved by combining the R-ADC and CL-ADC approaches to dispersion correction. Only glass types readily available in metre diameters are required.
Highlights
Mersenne Optical Consulting Ltd., Raumati Beach, Wellington 5032, New Zealand; Citation: Rakich, A
It will be shown that a corrector obtained by combining the first and third approaches described above (R-Atmospheric Dispersion Correctors (ADCs) and Compensating Lateral ADC” (CL-ADC)) achieves excellent correction of the secondary spectrum
This paper has investigated means of correcting secondary spectrum in meter-class correctors for large telescopes
Summary
Mersenne Optical Consulting Ltd., Raumati Beach, Wellington 5032, New Zealand; Citation: Rakich, A. For adaptive optics systems, operating at or near the diffraction limit imposed by the telescope aperture, R-ADC types incorporating glasses or crystals with anomalous relative partial dispersion have been employed to reduce secondary spectrum to tens of milliarc seconds [6,7]. The relative paucity of available glass types at meter-plus diameters limits the ability to correct secondary spectrum with R-ADC
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