For natural guide star observing, wavefronts may be corrected at full speed for objects of V ~ 11-12 magnitude, depending on conditions. For target stars as faint as V ~ 13.5-14, fewer corrections can be applied, but improvements in image quality over the natural seeing are possible.
If the target star is fainter than V~14 you may choose one of the following options.
1. Leave the mirror flat and do no corrections.
2. Use a very nearby (less than 20-30 arcseconds away) brighter star to correct on.
3. Close the loop on a nearby bright star and "fix" the shape of the mirror, then return to the target star. Keep the mirror stationary for the duration of the science observations.
When the f/15 is mounted the wind constraints are tighter to protect the deformable secondary mirror. If pointing into the wind and the wind is sustained at 25 mph or gusting above 30 mph, then we must close. If pointing away from the wind and the wind is sustained at 30 mph or gusting above 35 mph, the front shutters must be closed. Additionally, if the wind is coming out of the North-East or East, then it arrives at the telescope over Mt Wrightson and the ridge. This causes major turbulence above the telescope and will degrade the seeing and make it highly variable. In this case, there is nothing we can do to improve the conditions other than wait for the wind to change direction.
Overhead for setting up AO at the beginning of the night is estimated to be 30 minutes, with an additional 15 minutes for each new object during the night. Please include this in overhead estimates when planning your run.
For additional information on the MMT NGS-AO system performance see: "MMT AO Performance: Analysis and Status."
For a presentation of early science results, click here.
For more information, please contact adaptive optics scientist and engineer Keith Powell.
|Camera||Pixel Scale||Field of View||Diffraction limited||Limiting K mag*|
|Slit||Disperser||Camera||Resolving Power||Bands||Limiting K mag|
|low res grating||f/5.6||500 - 2000||JHKLM||18|
90" x 0.2"
|low res grating||f/5.6||3000||JHKLM||16.5|
90" x 0.4"
|low res grating||f/5.6||1500||JHKLM||16.5|
1" x 0.2"
Please Note that the LM band capabilities are not available currently. A large format 1-5 um detector is expected to be available in the future.
The Arizona Infrared imager and Echelle Spectrograph is designed to exploit the low thermal background and high optical throughput offered by the MMT's f/15 adaptive secondary system. With first imaging light achieved in 2003 and first spectra in 2007, ARIES is currently offered as a PI instrument. With three IR arrays, ARIES provides diffraction-limited imaging in the JHK(LM) atmospheric windows and long-slit and echelle spectroscopy at resolving powers from 1,500 to 50,000 (200 to 5 km/s). ARIES can also supply global wavefront tip/tilt information to the adaptive system using cryogenic pick-off mirrors to access field stars over a 90 arcsec diameter field at wavelengths from 1-2 microns.
ARIES consists of two dewars which share a common mount and vacuum. The 'purple dewar' is generally referenced as the imaging half of ARIES and also provides the spectrometer foreoptics. The 'green dewar' is generally referenced as the spectrometer half of ARIES. There is some cross-functionality between the two dewars: the imager contains a filter wheel that can provide slitless objective grism capabilities, and the spectrometer in turn has a grating selection mirror that can reference a flat mirror for wider field imaging.
To a greater or lesser degree, both halves of ARIES can be operated independently and simultaneously. Spectra of the science target can be acquired with the 'green' spectrometer while the spilt light in the slit plane can be imaged using the 'purple' camera.
Be aware that if you are applying to observe transits or obtain other time sensitive measurements with ARIES, it is unlikely that the instrument will be mounted at any time other than bright time. Please check whether your dates coincide with a bright moon phase before applying for time.
For further information please see the ARIES wiki.
Please return for the capabilities post-commissioning.
Binospec will exploit the wide field of view of the MMT with the f/5 secondary mirror by using dual identical but independent channels splitting the focal plane into two 8' x 15' FOV. Each channel has up to 4 gratings, 6 filters and a 4K E2V CCD (0.24" pixel sampling). The commissioning filters will offer broadband Sloan g, r, i, z
|256 x 256||further info|
|18 filters in two filter wheels||further info|
|available in wheel 1||further info|
The Mid-Infrared Array Camera and Bracewell Infrared Nulling Cryostat (MIRAC-BLINC) is an instrument developed for use with the adaptive optics system on the 6.5 m MMT. It has two main modes of operation: imaging at 8-25 microns, and nulling interferometry at 8-13 microns.
A fourth version of MIRAC (MIRAC4) saw first light in late October 2006. The camera features a 256×256 array with high quantum efficiency and low dark current. The camera is cooled using a pulse tube mechanical cooler which eliminates the need for liquid helium cooling. BLINC is a liquid nitrogen-cooled set of fore-optics for the MIRAC system.
The entrance window provides the reflection surface for the visible light to be sent to the AO wavefront sensor. The Cassegrain focus is reimaged by an off-axis ellipse within BLINC which is capable of being rotated to send the light to either the nulling interferometer or the imaging channel. The imaging channel forms an image of the secondary on a reflective cold stop which baffles out warm radiation from the telescope. The mirror at the cold stop is mounted on a rotating voice coil actuator. This allows chopping at 1-10 Hz within the cryostat.
The nulling interferometer splits the entrance pupil in half and overlaps these two beams on a 50% transmissive beamsplitter. Manual alignment of the beams can be achieved with feedthrough actuators. Pathlength changes are introduced by translating the beamsplitter mount using a stepper motor with 42 microns of motion per revolution. Small pathlength changes can be introduced by a PZT-mounted mirror in the right arm of the interferometer. Both outputs of the interferometer are sent to a NICMOS3 detector within BLINC to allow sensing of phase variations in the interferometer. One of the outputs has a short pass dichroic which sends 8-13 micron light to MIRAC.
For further information please see the MIRAC-BLINC wiki.
Blue Channel (Available): a low-to-intermediate resolution instrument optimized for spectroscopy in the range from 3200-8000 Å. A number of gratings are available giving resolution as high as 30 km/sec. Three gratings can be resident in the spectrograph at any one time, thereby facilitating rapid reconfiguration of the spectrograph. The current detector is a highly-optimized ITL/STA 2688x512 CCD. Instrument reference.
Red Channel (Available*): a 3.75" beam spectrograph optimized for the region 5000 Å to 1.0 μm but usable down to about 3700 Å. A highly-optimized ITL/STA 520x1032 fully depleted CCD is used as the detector. The spectrograph has several operating modes including high-throughput long-slit modes at a variety of spectral resolutions from 20 Å to about 2 Å and prism cross-dispersed modes yielding complete coverage from 4500 Å to 1.0 μm at moderate spectral resolution. As in the case of the Blue Channel, three gratings can reside in the spectrograph at any one time. Instrument reference. *There is a glow present in the Red Channel detector. Please see the Red Channel webpage.
Please follow the Blue and Red Channel links below to see tables of the fundamental capabilities.
For hints and tips on how to operate the instrument please see the Cheat Sheets.
The aperture wheel, the shutter, and the upper and lower filter wheels are used for both Blue and Red Channel.
The aperture plates are tilted 12.5° with respect to the optical axis to allow for reflection to a slit viewing acquisition and guide camera. The available aperture plates are listed in the table below. The aperture wheel will accept up to seven aperture plates at a time. One position in the wheel has been modified to allow the aperture to be changed while the spectrograph is mounted on the telescope. Observers may request any aperture plate for this position. The other six positions are typically populated with the 180" long slits excepting only the 0.75" wide slit.
The 20" and 9" slits are generally used for the Blue and Red Channel echellettes, respectively, in cross dispersed mode. The last two columns provide the FWHM of a Gaussian fit to an unresolved comparison lamp emission line as a function of the width of the entrance slit. In both cases a low-resolution grating was used, so the anamorphic factor is near unity. The CCDs were not binned on readout. Selecting the links in the table entries will display measured profiles.
Note that the comparison lines are not well approximated by a Gaussian for wider slits so the quoted FWHM are not particularly accurate.
Standard Slits: (√ = available)
|Slit Width (arcsec)||180" Length||20" Length||9" Length||Blue FWHM (pixels)||Red FWHM (pixels)|
Special Purpose Slits:
Comb - line of 1" diameter circular holes on 10" centers
3" diameter single circular hole
1.0", 1.4", and 5.0" diameter double circular holes
1.0" x 2.6" and 2.0" x 3.0" double slits
1.25" x 90" slit for use with the Blue Channel cross dispersing prism
90" circular hole for direct imaging
The finite size of the filter wheels vignettes light near the ends of the long slits. The unvignetted slit is about 150 arcsec long. The following links show plots of the intensity along the slit. For this data, the CCD was binned by a factor of two in the spatial direction, giving a spatial image scale of 0.6"/pixel, twice that of the nominal unbinned scale of 0.3"/pixel.
A Uniblitz shutter is located below the slit assembly and above the filter wheels. The shutter is controlled by the data acquistion computer and the CCD controller.
Each filter wheel has seven filter positions and one clear position. Each position can accommodate a 2-inch square filter with a thickness of up to ~6 mm. The available filters and their transmission curves are provided below. Filters cannot be changed while the spectrograph is mounted the telescope so please contact MMTO staff if you require a non-standard filter configuration. The two filter wheels are currently populated as follows:
The filter transmission curves provided below were measured in 1989 by Sally Oey using the monochromator at NOAO.
Blue Blocking Filters:
Red Blocking Filters:
The following filters are available to block light from lower orders. A plot of the filter transmission curves for the CuSO4 and U330 filters is available in pdf and png format and for the C-500 and CM-500 filters is available in jpg format and gif format. Or see the Hoya Color Compensating Filters Page.
Blue Channel Echellette Order Sorting Filters:
PDF plots of the echellette order-sorting filters are available below. Note that these are not usually resident in the spectrograph, so prospective users should contact the Instrument Specialist well in advance of their run.
The following standard Hoya Glass 2-inch square filters are kept on hand at the MMT. Consult a Hoya catalog for transmission curves. Note that these are not usually resident in the spectrograph, so prospective users should contact the Instrument Specialist well in advance of their run.
Information on the instrument rotator
|Grating (lines/mm)||Blaze (order/λ Å)||Blaze Angle(°)||Anamorphic Mag||R (@ Blaze, 1" slit)||Resolution (Å)||Dispersion (Å/pix)||Coveragea (Å)|
a Coverage is for the full 2688 columns. In practice the image quality may degrade slightly at the ends of the chip.
b May be limited by the blue cutoff or the free spectral range.
c Value of the free spectral range.
An illustration of the expected count rate (for a flat-spectrum (in F_nu) source of 1 micro-Jansky) per Angstrom is shown below.
NOTE: If you are submitting a proposal to use this configuration, please specify very clearly that this is the case in order to alert the telescope schedulers.
The Blue Channel Echellette grating is a 6" x 10", custom-ruled, 240 g/mm grating which can be used in orders 8-17 simultaneously, giving coverage from 3100-7000 Å with a 10 arcsecond long slit. Cross dispersion is provided by a large quartz prism which is inserted into the beam between the grating and the camera.
In a perfect spectrograph, the spectral resolution of this configuration is about 10,000 with a 1 arcsec wide slit (i.e. 30 km/sec). In practice, the focus degrades at the ends of the orders. During initial tests, we picked a focus value that gave a decent compromise focus over much of the frame. The resulting resolution varied from about 30 to 60 km/sec.
Several images which summarize the salient operating characteristics of this configuration are available as jpgs. Note that in these images, the 17th order is difficult to see or underexposed; while the order does not appear in these sample images, the data from the order is usable and calibratable. It is worth noting that the 8th order currently falls slightly off the detector near the atmospheric B-band. The percentage of the trace lost in this manner is small and will likely not strongly affect point source spectroscopy.
Throughput measurements are also not available for the cross-dispersed configuration. There is however historical evidence that on a photons/Å/second basis, this configuration is clearly not competitive with the other gratings -- we estimate that it may be a factor of 2 or more slower when compared to the other gratings at their blazed wavelengths. Some of this is attributable to losses from the prism; the rest (and probably the lion's share) is due to the grating. However, some of this factor is compensated for by the fact that one is atop the blaze in each of the echellette's orders as opposed to the normal gratings where the blaze can often compromise performance.
This grating could be very useful for projects requiring moderately-high resolution over a wide wavelength range. The data are relatively easy to reduce (up to the point where adjacent orders are combined) using the "echelle" package in IRAF.
Configuration of the spectrograph for cross-dispersed work requires that the spectrograph be taken off the telescope. In practice, this means that the spectrograph is scheduled for cross-dispersed "runs". It is possible to leave the prism in and use other gratings, but there is significant throughput loss and the spectra are quite curved. It is also possible to mount the Red Channel on the Blue Channel and use it for backup programs in case of inclement conditions.
Prospective users of the Echellette should contact Joannah Hinz.
The Red Channel detector has a glow. Please see below for details.
|Grating (lines/mm)||Blaze (order/λ Å)||Blaze Angle(°)||Anamorphic Mag||R (@ Blaze, 1" slit)||Resolution (Å or Å/order)||Dispersion (Å/pix)||Coveragea (Å)|
a Coverage is for the full 1032 columns.
b May be limited by the blue or red cutoffs or the free spectral range.
An illustration of the expected count rate (for a flat-spectrum (in F_nu) source of 1 micro-Jansky) per Angstrom is shown below.
In Fall 2014, the Red Channel detector developed a "glow" on the blue edge of the detector. This signal is well localized to the corner of the detector, so point source observations and observations focused on the red portion of the detector will likely be minimally effected. Observations of extended sources and programs that utilize the bluest portion of the observed spectrum may be impacted by the signal and its associated noise.
A two dimensional image of the bluest portion of the detector is shown below (the spectral direction of the detector runs in the Y-direction, so blue is up in the figure). The image is a bias-corrected dark image. The counts in the "glow" in the upper right depends on exposure time, so observers using long integrations are encouraged to take dark frames. On the right, we show the median counts in this 600s bias-subtracted dark frame in the last 3 columns; again, the bluest portion of the red channel image is at higher Y-pixel values.
Cross Dispersed Echellette Mode
The Red Channel Echellette grating gives complete coverage from 4300-8900 Å at a spectral resolution of a near-constant 90 km/sec when using a 1"x20" slit. Nominally it works in orders 7-13 but it can be used in orders 6-13 with some sacrifice of coverage in the blue and some order overlap between orders 6 and 7. Due to the Red Channel detector glow, we do not recommend the use of Echellette at this time.
The echellette should be used near its blaze at a tilt of 4.555 V (confirm, old value = 4.675), corresponding to a central wavelength of about 5250 Å in order 11. The cross-disperser should be set at 480 to put order 7 at the top of the frame; to get order 6 at the top, set the cross-disperser at 430.
Sample Echellette flat-field image: Blue is at the bottom and to the left. Orders are marked. This image was taken at a cross-disperser setting of 480. By judicious placement of the camera in the cross-dispersion direction, it is possible to include order 6, which is off the top of the frame, at the expense of a few hundred A in order 13.
Sample Echellette HeNeAr image: Strong Helium comparison lines are marked.
|512 x 1024, 18.5 micron pixels||further info|
|MKO M', Barr M', 3.1um, Barr L', 3 - 5um||further info|
|R = 8 - 157 (non-linear)||further info|
Clio is a 3-5 micron imager and coronagraph built to exploit the unique sensitivity and resolution of the MMT deformable secondary AO system. A particular area of focus for the instrument is to provide sensitive detection of giant planets at 3.8 and 4.8 microns. In spring 2010, the original 320×256 Indigo Systems InSb detector was replaced by a 512×1024 HAWAII HgCdTe detector. This upgrade allowed for more sensitive low background observations, while modestly reducing the allowable field size at M band.
For further information please see the CLIO wiki.
Hectochelle (Available-except for December 20 through January 20 due to cold temperatures; ambient air temp must be above 20°F): an echelle spectrograph operating at and R range of 32,000 - 40,000, and a wavelength range of 3800 - 9000Å. Due to optical properties the image from on 240 of the fibers fall on the Hectochelle detectors. It is a single order instrument and there are 11 order-separting filters available. The instrument contact is Andrew Szentgyorgyi. (Hectochelle is not considered a PI instrument for SAO and UAO observers.)
|Instrument||Grating (lpmm)||Spectral Range (Å)||Blaze Wavelength (Å)||Dispersion (Å/pix)||RMS image diameter (pix)|
|270||3650 - 9200||5200||1.21||5|
|600||5300 - 7800||6000||0.55||5|
|110||3800 - 9000||/||0.04||5|
Hectospec and Hectochelle are two large bench mounted spectrographs that are fiber fed by 300, 25m long optical fibers from the telescope's Cassegrain focus. A common to both spectrographs robotic positioner that is mounted behind the f/5 beam uses a pair of six-axis robots, dubbed Fred and Ginger, to reconfigure all 300 fibers over the 1deg focal surface to an accuracy of ~25um in just 300 seconds. Each fiber that is held magnetically on the focal surface has a core diameter of 250um that subtends to 1.5" on the sky. Adjacent fibers can be spaced as closely as 20" and is positioned using a complex algorithm.
Hectospec is a moderate-resolution, multiobject optical spectrograph, it offers 5770Å of spectral coverage at ~6Å resolution in the 350 to 1000 nm band. A higher dispersion grating offering ~3Å resolution is also available.
The Hectochelle adds a high dispersion capability to Hectospec's moderate dispersion with a second, very large bench-mounted spectrograph using an echelle grating. Hectochelle uses 240 of the possible 300 fibers and attains R~32,000 (sigma~4 km/s) over a single, filter-selected orders.
For greater details about the instruments, how to prepare for your observations, your reponsibilites, tips on data collection and reduction and links to all supporting documentation please see the Hectospec webpages and the Hectochelle webpages. IDL Software for the reduction of Hectospec data can be found here (please contract Joannah Hinz with any questions).
We are pleased to release version 2.0 of HSRED, incorporating a number of significant improvements provided by the Telescope Data Center at SAO. Key improvements include:
HSRED v2.0 can be downloaded via github. Just execute the following command:
As before, HSRED requires copies of both the idlutils and idlspec2d packages. HSRED v2.0 has been tested and verified to work with idlutils v5_5_15 and idlspec2d v5_7_1, but will also work with the (now ancient) versions of these packages needed for the old version of HSRED, so there is no need to update if you already have a working version.
Once you have downloaded all the pieces of code you need, continue following the instructions for setting up your environment variables here. Any installation or usage questions can be addressed by Joannah Hinz.
A new wrapper script is included with HSRED v2.0 that should streamline the reduction process. Step one is to place all the files you wish to reduce from a single night in a directory together: biases, dome and twilight flats, comparision lamp exposures, and any science exposures. You must include both the .fits files and their associated _map files. Sets of exposures using different gratings (270/600) or central wavelengths must be sorted and separated, one working directory per config (per night).
From your working directory, start idl and run the command:
for a standard reduction with cosmic-ray rejection, summed combination of exposures, red-leak removal, etc. The optional rerun keyword can be passed to make more than one reduction of the same dataset. If not specified, rerun will default to 0100 and your reduced data products will be placed in the subdirectory 'reduction/0100'.
If you have included F-stars in your target configuration, and wish to perform flux calibration as part of the coaddition, run:
Note that, for flux calibration, you must still add your stars and their photometry to the $HSRED_DIR/etc/standardstars.dat file, as described here. However, it should no longer be necessary to generate and use "plugcat" files. All info needed should now be read from the included _map files.
If your data was taken with the 600-line grating, you must specify the /do600 keyword, like:
For data obtained with an offset sky exposure (for sky-subtraction in crowded fields), the proceedure is a bit more complicated, and requires editing the lists/cal.list file. First, to reduce your science frames without the normal fiber-based sky subtraction, run
Next, the sky offset frame must be reduced separately. Edit the cal.list, commenting out the line for your science frames, and adding a new line giving the sky offset frames you wish to reduce (See the old page here for more on the format of the cal.list file, and remember it is no longer necessary to specify a plugcat.) Now, run the pipeline wrapper again. NOTE it is very important to use a different "rerun" number for this reduction, to avoid confusion with file names of the reduced data products.
The final step is to manually subtract the reduced sky offset frame from the reduced science frame, using the reduced data format and method of your choice.
Compared to earlier versions of HSRED, an expanded set of data products is generated, generally thanks to an enhanced version of hs_toiraf.pro which is called automatically within hs_pipeline_wrap. If you only wish to have the spHect* files, please just edit hs_pipeline_wrap.pro to comment out the relevant lines. There have also been minor changes to what is stored in the spHect* files, so in either case, please consult the description below:
skysub_/###.*.ms.fits: Subdirectory containing individual iraf-format spectra, linearized in wavelength, one file per fiber. Format is a 4543x1x4 cube. The 4 spectra in this cube are (in order):
If the pipeline was run with the /uberextract option, 1) and 2) will be the same, and contain the flux-calibrated, averaged spectrum (rather than one in coadded counts). This is true for all the data products described here.
.ms.fits : All 300 fibers in one file, with linearized wavelengths. This is a 4543x300x4 data cube, and the 4 elements along the 3rd dimension are the same as those described above for the single-fiber files.
spHect*fits: multi-extension fits file containing all coadded, sky-subtracted spectra for each hectospec configuration. Wavelengths are tabulated per pixel, rather than being described as a function in the fits header. The new, slightly altered data format is:
spObs*fits: multi-extension fits file containing sky-subtracted spectra for each individual science exposure (non-coadded). Format is similar to the coadded spHect files, but spObs files include the sky spectrum subtracted from each fiber on this exposure in HDU4
|selection ranging 0.3" - 2" (various lengths)|
Resolving power (0.7" slit)
|28,000 (7.5 km/s)|
Resolving power (0.3" slit)
|93,000 (3.2 km/s)|
MAESTRO (The MMT Advanced Echelle Spectrograph) is a Cassegrain mounted, optical, slit single, high-resolution echelle spectrograph which uses the MMT f/5 secondary, spectroscopic corrector, wavefront sensor and ADC. MAESTRO has a 4096 x 4096 CCD with 15μm pixels that has been optimized for the UV by the UA Imaging Technology Lab (ITL).
The design of MAESTRO was driven by the desire to do multi-order spectroscopy of a single object with a wide wavelength coverage extending to the atmospheric cut-off in the UV. It is optimized for multi-order, simultaneous wavelength coverage, with R = 28,000, or 7.5 km/s when used with a 0.7" slit. The best possible spectral resolution, using a 0.3" slit, is Nyquist sampled with spectral resolution of R=93,000 or 3.2 km/s. The single exposure wavelength coverage is 3150 to 9850Å with small gaps redward of about 8000Å.
For further details please see the MAESTRO homepage.
MMIRS has returned from Magellan and now resides permanently at the MMT. MMIRS observing is run in queue mode. Astronomers do not need to be present at the MMT for their observations. If you have questions about queue observing, please contact Joannah Hinz.
See this paper for more information on the instrument upgrades and the publicly available IDL data reduction pipeline.
Getting Your Data:
After an observing run, an MMT staff member will contact you with the details of which observations were completed from your program. Raw data can be obtained by emailing the SAO Telescope Data Center helpdesk.
|20" x 40"|
FWHM at 2.2 µm with AO
|At 2.2 µm 18.1 mag/arcsec^2, S/N=3/1 in 2 hrs|
|At 3.1 µm 15.9 mag/arcsec^2, S/N=3/1 in 2 hrs|
Point Source Polarimetry
|At 2.2 µm m=14.6, P=+/-1% in 2 hrs|
Point Source Polarimetry
|At 3.1 µm m=12.2, P=+/-1% in 2 hrs|
MMTPOL is an adaptive optics optimized imaging polarimeter for use at the 6.5m MMT. By taking full advantage of the adaptive optics secondary mirror of the MMT, this polarimeter offers diffraction-limited polarimetry with very low instrumental polarization. The advent of AO secondary mirrors (e.g., Brusa et al. 2003) offers the chance to observe at the diffraction limit of large telescopes but with negligible increased instrumental polarization. The combination of a large collecting area, an AO system with no off-axis reflections, and an optical design approach to offer precision polarimetry, will permit polarimetric images in the 1-5μm region at higher precision at the diffraction limit than any other polarimeter.
|f/9||f/15 NGS||f/15 LGS|
|1 - 2.5um||1 - 2.5um||1 - 2.5um|
|3.16 arcminutes||26.4 arcseconds||1.9 arcminutes|
|0.185 "/pixel||0.026 "/pixel||0.11 "/pix|
PISCES is a JHK wide field imager that was initially designed and built as a test bed for a Hawaii-I detector and used in conjunction with the f/9 secondary and was later used with the adaptive f/15. PISCES can reimage the focal plane from any telescope with an f-ratio #9 onto the 1024 x 1024 Hawaii CCD. It uses accurate pupil reimaging and cold baffling to block the thermally emissive structures associated with operating at the Cassegrain focus. The optical design was driven by the desire to optimize the spot sizes for the K band but also seeing-limited performance in the J and H bands.
For further information please see the PISCES webpages.
|4 - 15Å|
|3800 - 9000Å|
|~36% @ 5500 - 6000Å|
SPOL is an imaging spectropolarimeter that can be configured with either a λ/2 or λ/4 rotatable achromatic retardation plate to provide linear or circular polarization measurements, respectively. A thin Wollaston prism, which has very high throughput and polarimetric efficiency, is used as the polarization analyzer. In spectroscopic mode a number of slit widths and gratings are available. For the imaging mode, a large square 19" x 19" aperture is used and a flat mirror replaces the grating. The two polarized beams that emerge from the prism are reimaged as either complementary parallel spectra (spectroscopic mode) or complementary polarized images (imaging mode) on the CCD detector. The polarimetric efficiency (the degree of polarization measured for a completely polarized source) exceed 95% over a range of 4500-8000Å.
The instrument and camera are controlled with a single PC that is programmed to coordinate motion control (shutters, wave plates, etc) and image acquisition. The aperture plate is tilted to provide reimaging to a CCD guide camera for target acquisition and guiding.
An "observation" is the measurement of a Stokes parameter in a sequence of exposures, with polarimetric modulation occurring following readout via rotation of the wave plate. Individual frames are co-added in computer memory according to wave plate orientation, producing two complementary images in orthogonal senses of polarization. These are compared during data reduction to obtain the degree of polarization Q, U, or V.
Data reduction is performed using custom IRAF scripts that are available from the PI. These scripts are comprehensive and straight forward to use and therefore non-polarimetrists can achieve robust results. For information please see the SPOL website.
|5.12 x 5.12 arcminutes|
|Y (1.02um), J (1.2 um), H (1.6um)|
The SAO Widefield InfraRed Camera (SWIRC) was designed with the goal to be a quickly delivered, wide FOV IR imager with minimum optical elements to give the MMT YJH ability with very high throughput. The instrument was proposed in May 2003 and successfully commissioned at the MMT just over 12 months later. The only trade-off for speed of completion was to sacrifice K-band capability by not including an internal, cold Lyot stop. The instrument is mounted at the f/5 focus without the imaging corrector optics as the dewar window acts as the field flattening lens. SWIRC has three science filters and one dark slide giving it an observing range of ~0.9μm to ~1.8μm. The instrument uses a 2048 x 2048 Hawaii-II detector with a plate scale of 0.15”/pixel to fully sample the best seeing at the MMT site over the 5.12’ x 5.12’ FOV.
For further details please the SWIRC website
|SDSS u, g, r, i, z*|
|2.7 x 2.7 arcminutes|
MMTCam is an instrument for the MMT commissioned by Warren Brown in November 2012. The f/5 wavefront sensor system serves as the platform on which the imager is installed. The associated filters have central wavelengths of 355nm, 469nm, 616nm, 748nm, and 893nm. Binning can be set to 2 x 2 if faster read-out is desired. Because the f/5 secondary is mounted on the MMT for approximately 30% of available telescope time, the MMTCam enables a rapid-response imaging capability for the MMT for use on targets of opportunity, transients and monitoring of objects such as supernovae for longer term projects, without requiring an instrument change. We highly recommend requesting only dark or grey time with this instrument. For more information, including camera manual, please go here.