A Direct Measurement of Atmospheric Dispersion in N-band Spectra: Implications for Mid-IR Systems on ELTs
Abstract
Adaptive optics will almost completely remove the effects of atmospheric turbulence at 10 μm on the Extremely Large Telescope (ELT) generation of telescopes. In this article, we observationally confirm that the next most important limitation to image quality is atmospheric dispersion, rather than telescope diffraction. By using the 6.5 m MMT with its unique mid-IR adaptive optics system, we measure atmospheric dispersion in the N band with the newly commissioned spectroscopic mode on MIRAC4-BLINC. Our results indicate that atmospheric dispersion is generally linear in the N band, although there is some residual curvature. We compare our measurements to theory, and make predictions for ELT Strehls and image FHWM with and without an atmospheric dispersion corrector (ADC). We find that for many mid-IR applications, an ADC will be necessary on ELTs.
The observations reported here were obtained at the MMT Observatory, a facility operated jointly by the Smithsonian Institution and the University of Arizona.- Publication:
-
Publications of the Astronomical Society of the Pacific
- Pub Date:
- August 2009
- DOI:
- 10.1086/605312
- arXiv:
- arXiv:0906.2196
- Bibcode:
- 2009PASP..121..897S
- Keywords:
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- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 22 pages, 8 figures, accepted to PASP