The Binospec spectrograph will be installed at the MMT telescope. Binospec is a multislit imaging spectrograph with two 8' x 15' fields of view, wide wavelength coverage, and high efficiency. There are two identical all-refractive spectrographs, one for each field. Each channel has several gratings and filters.
This page provides preliminary information about Binospec for potential users and proposers. Binospec is currently scheduled for commissioning in fall/winter 2017; pending commissioning, it may be available for shared-risk observing in spring 2018.
Each side has a 4K x 4K deep depleted E2V CCD detector with 15 micron pixels and a scale of 0.24 arcsec/pixel.
Slitmasks will be machined by a laser cutter at the MMT. Slitmasks will be configured by software written at SAO and running on a server hosted at the MMT. Users will log into a web interface to interactively design masks and submit them. Masks must be configured ahead of time to allow time for machining. Long slits will also be provided (of width ?). 10 slitmasks can be loaded simultaneously. Masks can be changed during the daytime (and potentially during the night pending approval of this mode and training of staff).
|Grating lines/mm||Order||Blaze angle||Angle of incidence||Ana. Demag.||Coverage (A)||Dispersion (A/pixel)||Pixels per 1'' slit||Resolution in 1'' slit|
|Grating lines/mm||Allowable central wavelengths|
|270||5501 - 7838 A|
|600||5146 - 8783 A|
|1000||4108-4683, 5181-7273, 7363-7967, 8153-8772, 8897-9279|
|Ghosts may be troublesome with 1000 gpm grating at
central wavelengths 5600-8500 A, worst near 7100 A.|
Throughput of 1000 gpm grating will be low in the red.
The paired fields of view on the sky are shown below in yellow - the separation between them is ? in arcmin. The green boxes are the guider patrol regions, and the orange box is the wavefront sensor patrol region. The labeled dimensions in mm are in the telescope focal plane, not the CCD plane. The slitmasks cover the guider regions and holes are machined into into the masks at the location of guide stars, to allow for slitmask alignment and guiding.
Binospec can hold 10 slitmasks, and these can be changed out freely during the day (unlike MMIRS), and potentially at nght. However, there is a lead time for machining masks.
The grating tilt controls wavelength coverage. We anticipate that a limited number of standard grating tilts will usually/initially be used, to ease calibration requirements and configuration changes during the night. The instrument can be changed from spectroscopic to imaging mode quickly, and will have g, r, i, z filters for each side. We do not anticipate initially offering mixed observing between the sides (ie imaging + spectra, or two different gratings).
Note that the differential atmospheric refraction across the 15 arcminute field is significant, so that the location of slitlets depends on the hour angle at which the mask is observed. In practice this means that the mask machining would change slightly depending on whether the mask is observed when HA is East or West. Thus the date and time of observation specified during mask design are significant. Observable hour angles will be taken into account during queue scheduling.
An interface similar to the MMIRS user interface will allow PIs to submit mask designs and track their program progress. There will be a materials/machining charge of ? ($250 ??) per slitmask.