Design and Fabrication of a lightweight three-lens corrector system for the 2.34-m Vainu Bappu Telescope

Fuente: arXiv
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Main Authors: Singh, Nitish, Sriram, S., Sethuram, Ramya, Yerra, Bharat Kumar, Burman, Rahuldeb, Nataraj, G., Chethan, C, Kemkar, P. Madan Mohan, Sagayanathan, K, Das, Saikat, J, Francis Xavier Rozario
Format: Preprint
Published: 2025
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author Singh, Nitish
Sriram, S.
Sethuram, Ramya
Yerra, Bharat Kumar
Burman, Rahuldeb
Nataraj, G.
Chethan, C
Kemkar, P. Madan Mohan
Sagayanathan, K
Das, Saikat
J, Francis Xavier Rozario
author_facet Singh, Nitish
Sriram, S.
Sethuram, Ramya
Yerra, Bharat Kumar
Burman, Rahuldeb
Nataraj, G.
Chethan, C
Kemkar, P. Madan Mohan
Sagayanathan, K
Das, Saikat
J, Francis Xavier Rozario
contents The Vainu Bappu Telescope (VBT) is a 2.34-m reflector, primarily supported on-axis field of view, offering high-resolution and low-to-medium resolution spectroscopic observations in its prime and Cassegrain configurations. This study presents the design and fabrication of a compact, lightweight, three-element wide-field corrector (WFC) utilizing three spherical lenses to cover a polychromatic wavelength range over a 30$'$ FoV at prime focus. The WFC design was optimized using ZEMAX, ensuring precision in aberrations, tolerances, and atmospheric dispersion. The fabricated lenses met stringent tolerances, with a $\pm$1 mm deviation in radius of curvature and $\pm$2 mm deviation in center thickness. A mechanical mount was developed to integrate all the WFC lenses, and wavefront error testing for the WFC system was performed using ZYGO interferometry, yielding a Wavefront Error of 0.05 $λ$. Laboratory performance tests were designed and conducted using a dedicated setup with achromatic lenses and 100 $μm$ fiber-coupled polychromatic light source showed a deviation of 0.1 pixel on-axis and 0.5 pixel at the extreme off-axis field compared to the ZEMAX design, demonstrating that the optical performance of WFC is with minimal aberrations across the entire FoV. The successful integration of the WFC at the VBT prime focus will increase the FoV, enabling the multi-fiber, multi-spectrograph setup in 30$'$ field that will facilitate both OMR and Echelle spectrograph to be used on the same night along with the addition of new multi-object spectrograph and an integral field unit instrument. This will mark a significant upgrade for the VBT, broadening its research potential, and expanding its observational versatility.
format Preprint
id arxiv_https___arxiv_org_abs_2504_10872
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Design and Fabrication of a lightweight three-lens corrector system for the 2.34-m Vainu Bappu Telescope
Singh, Nitish
Sriram, S.
Sethuram, Ramya
Yerra, Bharat Kumar
Burman, Rahuldeb
Nataraj, G.
Chethan, C
Kemkar, P. Madan Mohan
Sagayanathan, K
Das, Saikat
J, Francis Xavier Rozario
Instrumentation and Methods for Astrophysics
The Vainu Bappu Telescope (VBT) is a 2.34-m reflector, primarily supported on-axis field of view, offering high-resolution and low-to-medium resolution spectroscopic observations in its prime and Cassegrain configurations. This study presents the design and fabrication of a compact, lightweight, three-element wide-field corrector (WFC) utilizing three spherical lenses to cover a polychromatic wavelength range over a 30$'$ FoV at prime focus. The WFC design was optimized using ZEMAX, ensuring precision in aberrations, tolerances, and atmospheric dispersion. The fabricated lenses met stringent tolerances, with a $\pm$1 mm deviation in radius of curvature and $\pm$2 mm deviation in center thickness. A mechanical mount was developed to integrate all the WFC lenses, and wavefront error testing for the WFC system was performed using ZYGO interferometry, yielding a Wavefront Error of 0.05 $λ$. Laboratory performance tests were designed and conducted using a dedicated setup with achromatic lenses and 100 $μm$ fiber-coupled polychromatic light source showed a deviation of 0.1 pixel on-axis and 0.5 pixel at the extreme off-axis field compared to the ZEMAX design, demonstrating that the optical performance of WFC is with minimal aberrations across the entire FoV. The successful integration of the WFC at the VBT prime focus will increase the FoV, enabling the multi-fiber, multi-spectrograph setup in 30$'$ field that will facilitate both OMR and Echelle spectrograph to be used on the same night along with the addition of new multi-object spectrograph and an integral field unit instrument. This will mark a significant upgrade for the VBT, broadening its research potential, and expanding its observational versatility.
title Design and Fabrication of a lightweight three-lens corrector system for the 2.34-m Vainu Bappu Telescope
topic Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2504.10872