Binospec: A Wide-field Imaging Spectrograph for the MMT

• Published in: arXiv.org 2019-05
• Main Authors: Fabricant, Daniel, Fata, Robert, Epps, Harland, Gauron, Thomas, Mueller, Mark, Zajac, Joseph, Amato, Stephen, Barberis, Jack, Bergner, Henry, Brennan, Patricia, Brown, Warren, Chilingarian, Igor, Geary, John, Kradinov, Vladimir, McLeod, Brian, Smith, Matthew, Woods, Deborah
• Format: Article
• Language: English
• Subjects: Active control; Alignment; Apertures; Collimation; Flexing; Gratings (spectra); Masks; Offsets; Slits; Stainless steels; Target acquisition; Target masking; Wave front sensors
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1905.03320

Binospec is a high throughput, 370 to 1000 nm, imaging spectrograph that addresses two adjacent 8' by 15' fields of view. Binospec was commissioned in late 2017 at the f/5 focus of the 6.5m MMT and is now available to all MMT observers. Aperture masks cut from stainless steel with a laser cutter are used to define the entrance apertures that range from 15' long slits to hundreds of 2" slitlets. System throughputs, including the MMT's mirrors and the f/5 wide-field corrector peak at ~30%. Three reflection gratings, duplicated for the two beams, provide resolutions (\(\lambda\)/\(\Delta \lambda\)) between 1300 and \(>\)5000 with a 1" wide slit. Two through-the-mask guiders are used for target acquisition, mask alignment, guiding, and precision offsets. A full-time Shack-Hartmann wave front sensor allows continuous adjustment of primary mirror support forces, telescope collimation and focus. Active flexure control maintains spectrograph alignment and focus under varying gravity and thermal conditions.