DragonflyPol: Wide-Field Optical Linear Polarimetry with the Dragonfly Telephoto Array (Instrument Description and Commissioning)
Abstract
We present DragonflyPol, a wide-field optical linear polarimetry capability implemented on the Dragonfly Telephoto Array. DragonflyPol leverages Dragonfly's modular, multi-lens architecture to obtain simultaneous measurements in four linear polarization orientations (0∘, 45∘, 90∘, and 135∘) across a ∼5 deg2 field of view, distributed across 44 polarized lens--detector units. Four additional units serve as unpolarized reference channels. We describe a broad range of science goals enabled by this capability, including magnetic field mapping and tomography, dust grain properties, CMB foreground characterization, and the three-dimensional structure of diffuse interstellar clouds. We integrate Canon polarizers and Baader Sloan r' bandpass filters into the drop-in filter holders of the Canon lenses, and conduct a three-phase laboratory characterization program to select optimal polarimetric components, measure contrast ratios and transmission efficiencies, and determine and mark the transmission axis of each polarizer with sub-degree repeatability. Laboratory measurements across all 44 deployed polarizers yield a mean noise-subtracted contrast ratio of 1228 ± 104 and a single-polarizer transmission efficiency of ∼33\% in the r' band. On-sky commissioning, including twilight flat-field characterization and twilight-sky polarization measurements, confirms throughput stability across polarization groups and successful recovery of the expected Rayleigh scattering signal. DragonflyPol achieved first polarimetric light in September 2025.
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BibTeX
@misc{tahani2026dragonflypol,
title = {{DragonflyPol: Wide-Field Optical Linear Polarimetry with the Dragonfly Telephoto Array (Instrument Description and Commissioning)}},
author = {Mehrnoosh Tahani and Leo Hollberg and Hiroshi Akitaya and Jaeyeon Kim and Deborah Lokhorst and Roberto Abraham and Pieter van Dokkum and William P. Bowman and Vishwa Koshene Gamage and Paras Regmi and Yasuo Doi and Koji S. Kawabata},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.14258},
eprint = {2607.14258},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.14258},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - DragonflyPol: Wide-Field Optical Linear Polarimetry with the Dragonfly Telephoto Array (Instrument Description and Commissioning)
AU - Mehrnoosh Tahani
AU - Leo Hollberg
AU - Hiroshi Akitaya
AU - Jaeyeon Kim
AU - Deborah Lokhorst
AU - Roberto Abraham
AU - Pieter van Dokkum
AU - William P. Bowman
AU - Vishwa Koshene Gamage
AU - Paras Regmi
AU - Yasuo Doi
AU - Koji S. Kawabata
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2607.14258
UR - https://arxiv.org/abs/2607.14258
AB - We present DragonflyPol, a wide-field optical linear polarimetry capability implemented on the Dragonfly Telephoto Array. DragonflyPol leverages Dragonfly's modular, multi-lens architecture to obtain simultaneous measurements in four linear polarization orientations (0^∘, 45^∘, 90^∘, and 135^∘) across a ∼5 deg^2 field of view, distributed across 44 polarized lens--detector units. Four additional units serve as unpolarized reference channels. We describe a broad range of science goals enabled by this capability, including magnetic field mapping and tomography, dust grain properties, CMB foreground characterization, and the three-dimensional structure of diffuse interstellar clouds. We integrate Canon polarizers and Baader Sloan r' bandpass filters into the drop-in filter holders of the Canon lenses, and conduct a three-phase laboratory characterization program to select optimal polarimetric components, measure contrast ratios and transmission efficiencies, and determine and mark the transmission axis of each polarizer with sub-degree repeatability. Laboratory measurements across all 44 deployed polarizers yield a mean noise-subtracted contrast ratio of 1228 ± 104 and a single-polarizer transmission efficiency of ∼33\% in the r' band. On-sky commissioning, including twilight flat-field characterization and twilight-sky polarization measurements, confirms throughput stability across polarization groups and successful recovery of the expected Rayleigh scattering signal. DragonflyPol achieved first polarimetric light in September 2025.
ER -