The Dragonfly Spectral Line Mapper: Completion of the 120-lens array

TL;DR

The paper reports the completion and commissioning of the Dragonfly Spectral Line Mapper, a 120-lens mosaic telescope designed for ultra low surface brightness imaging, including new instrumentation and characterization of the system.

Contribution

It presents the final design, instrumentation, and characterization of the fully assembled 120-lens array, and discusses prospects for a larger 1000-lens system.

Findings

Successful deployment of 120-lens array

Implementation of image stabilization with Dragonfly StarChaser

Characterization of cameras and filters for the full array

Abstract

The Dragonfly Spectral Line Mapper is a mosaic telescope comprising 120 Canon telephoto lenses, based on the design of the Dragonfly Telephoto Array. With a wide field of view, and the addition of the "Dragonfly Filter-Tilter" instrumentation holding ultra narrow bandpass filters in front of each lens, the Dragonfly Spectral Line mapper is optimized for ultra low surface brightness imaging of visible wavelength line emission. The Dragonfly Spectral Line Mapper was constructed and commissioned in four phases from March 2022 to November 2023. During this time, four individual mounts of 30 lenses each were constructed and commissioned. The commissioning of the telescope included the deployment of the "Dragonfly StarChaser" which carries out image stabilization corrections in the telephoto lens, to enable hour-long exposures to be taken. In addition, we introduced new instrumentation such as a film to cover the optics to keep the filters clean. Here we describe the updated design of the complete 120-lens array, and the implementation of the instrumentation described above. Additionally, we present updated characterization of the cameras and filter transmission for the full array. Finally, we reflect on the construction and commissioning process of the complete 120-lens array Dragonfly Spectral Line Mapper, and remark on the feasibility of a larger 1000-lens array.