[Paper Review] Wide-field telescopes with a Mangin mirror

V. Yu. Terebizh|ArXiv.org|Oct 11, 2007

Advanced optical system design1 references3 citations

TL;DR

This paper presents two all-spherical, catadioptric wide-field telescope designs using a Mangin mirror: Design A (500 mm aperture, f/2.0) achieves a 7° flat field with near-diffraction-limited images (D80 ≈ 1.3–2.2 arcseconds), while Design B (1000 mm aperture, f/1.7) delivers a 10° field with D80 ≈ 1.5–1.9 arcseconds. Both use double-pass corrector lenses and simple glasses (N-BK7, fused silica), enabling low-cost, high-quality wide-field imaging with minimal obscuration and stray light.

ABSTRACT

Two all-spherical catadioptric optical systems with a Mangin mirror are described. The design A (aperture 500 mm, f/2.0) has flat field of view of 7 deg in diameter; the design B (aperture 1000 mm, f/1.7) has 10-deg flat field. Both designs show near-diffraction-limited images. The D_80 diameter for the design A in the integral waveband 0.45-0.85 mcm varies from 1''.3 on the optical axis up to 2''.2 at the edge of the field (6.2-10.7 mcm); the corresponding range of the D_80 diameter for the design B is 1''.5-1''.9 (12.4-16.2 mcm). The designs include simple glass types, mainly Schott N-BK7 and fused silica. In case of need, better images could be attained by a choice of other glass, aspherisation of some surfaces, etc.

Motivation & Objective

• To develop large-aperture, wide-field telescopes with spherical optics that maintain high image quality.
• To extend the usable field of view of Mangin mirror telescopes beyond traditional limits using double-pass corrector lenses.
• To minimize obscuration and stray light while maintaining near-diffraction-limited performance.
• To demonstrate feasibility using only standard, low-cost glass types (e.g., N-BK7, fused silica) and spherical surfaces.
• To provide a scalable, cost-effective design framework for wide-field astronomical imaging.

Proposed method

• Employ a remote aperture stop to reduce aberrations and minimize light obscuration (23% vignetting in Design A).
• Use a large corrector lens in double-pass mode to correct spherical and coma aberrations across wide fields.
• Implement a two-lens exit corrector made of standard glasses (e.g., N-BAK2 and N-BASF64) to further refine image quality.
• Optimize the Mangin mirror configuration with spherical surfaces to maintain simplicity and manufacturability.
• Utilize ZEMAX optical design software to model and refine system performance across the full field of view.
• Select glass types based on availability, cost, and refractive properties to balance performance and practicality.

Experimental results

Research questions

• RQ1 Can a wide-field telescope with a Mangin mirror achieve near-diffraction-limited image quality across a 7°–10° field using only spherical surfaces?
• RQ2 How can double-pass corrector lenses be used to extend the field of view and improve image quality in all-spherical Mangin-based systems?
• RQ3 What is the optimal combination of standard glass types to achieve high image quality at low cost in large-aperture designs?
• RQ4 To what extent can obscuration and stray light be minimized in such systems while maintaining wide-field performance?
• RQ5 Can the performance of these systems be further enhanced through aspherization or advanced exit correctors without abandoning spherical optics?

Key findings

• Design A (500 mm aperture, f/2.0) achieves a 7° flat field with D80 diameter ranging from 1.3 arcseconds at the center to 2.2 arcseconds at the edge in the 0.45–0.85 μm band.
• Design B (1000 mm aperture, f/1.7) delivers a 10° field with D80 diameter of 1.5–1.9 arcseconds, indicating near-diffraction-limited performance.
• The systems exhibit only 0.50% maximum distortion in Design A and 0.23% in Design B, confirming excellent field flatness.
• Vignetting is minimal, with 76.8–76.9% of rays unvignetted across the field in Design A and 72.8% in Design B.
• The use of fused silica and N-FK5 glass in Design B improves transmission and thermal stability compared to N-BK7.
• Image quality can be further enhanced via aspherization or advanced multi-lens exit correctors (e.g., using N-FK51A or N-PK52A), enabling sub-arcsecond performance.