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Wadsworth mount redux: paraboloidal versus spherical gratings
William R Hunter1, Michael P Kowalski, Raymond G Cruddace
1SFA, Incorporated, Woodlands Office Center, 9315 Largo Drive West, Suite 200, Largo, Maryland 20774, USA. wrhunter@bellatlantic.net
Applied Optics
|December 3, 2003
Summary
Paraboloidal diffraction gratings offer higher resolution than spherical gratings for astrophysical plasma investigations. This improvement in satellite spectrographs is due to reduced coma effects in paraboloidal designs.
Area of Science:
- Astrophysics
- Plasma Physics
- Optical Engineering
Background:
- Satelliteborne spectrographs are crucial for investigating astrophysical plasmas.
- Diffraction gratings are key components in spectrographs, determining spectral resolution.
- Spherical gratings are commonly used but have limitations in optical aberrations.
Purpose of the Study:
- To compare the resolution of spherical and paraboloidal diffraction gratings for satellite spectrographs.
- To evaluate grating performance in the 100-300 A spectral region for astrophysical plasma studies.
- To identify optimal grating types for enhancing spectrograph capabilities.
Main Methods:
- Utilizing eight spectrographs with Wadsworth mounts in near-normal incidence.
- Employing effective focal lengths of 3 m for each spectrograph.
- Conducting ray tracing simulations to analyze grating performance and aberrations.
Main Results:
- Paraboloidal gratings show a significant increase in resolution compared to spherical gratings.
- This resolution enhancement is observed in Wadsworth mounts with small spectral ranges (approx. 10% of central wavelength).
- The improved resolution is attributed to the reduced spatial extent of coma in paraboloidal gratings.
Conclusions:
- Paraboloidal diffraction gratings are superior to spherical gratings for specific spectrograph applications.
- The findings support the use of paraboloidal gratings to enhance the study of astrophysical plasmas.
- Optimized grating selection can significantly improve the performance of space-based observational instruments.