Page Last Updated : Jan 7 15:43
Contributors: B. McLeod, J. Bechtold, W. Brown, M. Conroy, F. DiMille, M. Hastie, V. Suc, A. Szentgyorgyi, D. Osip, J. Roll, Y. Beletsky, I. Chilingarian
Last update November 2012
MMT and Magellan InfraRed Spectrograph (MMIRS) is a near infrared (NIR) imager and multi-object spectrograph with a 6.9'x 6.9' imaging field-of-view. The focal plane is a 2048x2048 pixel Hawaii2 detector with 18 micron pixels which subtend 0.2 arcsec on a F/5, 6.5m telescope. The instrument offers imaging, long-slit spectroscopy through a variety of slit widths, and multi-object spectroscopy over a 4' x 6.9' field of view. Grisms supporting spectroscopy at R=2400 and R=1200 are available. The dual guide-probe/wavefront sensor enables continuously updated wavefront sensing. The major subsystems of MMIRS are shown in Figure 1.
Figure 1 Cut-away CAD drawing of the MMIRS cryotstat components. Major features not shown are the gatevalve and the mask section LN2 tank.
The PI of the MMIRS program is Brian McLeod, CfA. He may be contacted at firstname.lastname@example.org. The design, contruction and integration at the MMT and Magellan was the work of CfA scientists and engineers, especially from the SAO Central Engineering Department. MMIRS was constructed with funding from the National Science Foundation, Harvard College Observatory and the Smithsonian Astrophysical Observatory.
Web pages with complementary information about MMIRS are:
http://www.cfa.harvard.edu/mmti/mmirs.html Top level page
http://www.cfa.harvard.edu/mmti/mmirs/instrstats.html This page contains a description of the available filters and grisms.
See also McLeod, et al. (2012) MMT and Magellan Infrared Spectrograph, PASP, 124, 1318, d/PASP_MMIRS_2012.pdf Please cite this paper when publishing your MMIRS results.
MMIRS has been operated at both the MMT and the Clay (Magellan 2) Telescope at Las Campanas. It is currently available at Magellan.
MMIRS is a near infrared (NIR) spectrograph and imager that has a passband that extends from Y to K band (0.9-2.4 microns). The science detector is a Teledyne Hawaii2, 2k x 2k, 18 micron pixel HgCdTe detector. The detector has four quadrants and each quadrant is read out through 8 channels. The full well is 230,000 e- & the gain is 5 e-/ADU (full well is 46,000 ADU). Detector response starts to become non-linear above approximately 40,000 ADU. The array is read out by a controller designed at CfA, based on a scalable architecture used in all CfA F/5 instrumentation at Magellan & the MMT.
The various modes and functions of MMIRS are selected with a combination of five independent wheels - the Dekker (aperture selection) wheel, the slit/slit mask wheel, two filter wheels, and the grism wheel (see Figure 1.). The MMIRS mask wheel has a combination of 9 slots for custom masks, 7 fixed long slits and 1 imaging aperture. The grism wheel can hold up to 5 grisms with one clear slot for imaging. At this time there are three grisms: H+K @ R=1200, J @ R=2400 and H @ R=2400. This spectral resolution is achieved with a 0.4" slit. The available long slits are 1, 2, 3, 4, 6, 8 and 12 pixels in width (each pixel is 0.2") - See Figure 2. The filter wheels can hold up to 10 filters with one clear slot for imaging. The initial complement of filters are Y, J, H & Ks plus blocking filters of 1.25-2.5 microns and 0.95-1.5 microns.
Figure 2 The MMIRS Mask Wheel
MMIRS has two guide/wavefront sensing (GWFS) units. Typically one unit is used for standard guiding while the other probe does continuous WFS and provides guide information for rotator guiding. There is no slit viewing camera.
The MMIRS cryostat is divided into two chambers - the slit mask (MOS) section and the camera section. The two dewar sections are separated by a gate valve. When the masks need to be changed out the gate valve is closed and the mask dewar is warmed up to room temperature using internal heaters The change over of slit masks will be completed by Observatory staff during the day and the MOS dewar will be returned to operating temperature before sunset. The gatevalve is operated by the Observatory staff. The second dewar, the camera dewar, remains at operating temperature through out the whole MMIRS run. Both dewars are cooled by LN2. The MOS dewar has a hold time of 36 hours when a MOS mask change is not done during the day and the camera dewar has a hold time of 48 hours. Observatory staff are responsible for keeping the dewars filled with LN2 - if you detect any change in operating temperature please inform the Observatory staff.
The salient features of MMIRS are tabulated in Table 1.
|Detector Type||Teledyne Hawaii2 HgCdTe|
|Pixels||2048 x 2048|
|Pixel Size||18 microns|
|Field-of-View (imaging)||6.8 x 6.8 arcmin|
|Field-of-View (spec)||4 x 6.8 arcmin|
|Plate Scale at slit||0.169 mm/arcsec|
|Pixel Scale||0.2 arcsec/pixel|
|Readout Time||0.7s for a single read|
|Minimum Exposure time||1s (must increase in integer seconds)|
|Typical overhead per exposure||7-17s (depending on size of file, dither size)|
|Typical spectroscopic overheads|| 5-10 min for acquisition and mask alignment
5 min for calibration frames (comps + flats)
5-10 min for telluric setup and data taking
|Digitization||16 bit (65,536 ADU)|
|Readnoise||16 e- per read|
|Median Detector QE||J:69%, H:79%, K:73%|
|Median Dark current||0.06e-/pix/sec|
|Full well||~230,000 e- (46,000 ADU) (non-linear above 40,000ADU)|
|Fits File Size||approx 16804800 bytes per readout|
|Imaging Filters||Y, J, H, Ks|
|Spectroscopic Filters||HK, zJ|
|Grisms available||R=1200@HK, R=2400@H, R=2400@J|
|Calibration lamps||Dim Incand, Bright Incand, Argon|
The Hawaii2 science array is a HgCdTe device with 18 micron pixels and sensitive from 0.9 - 2.4microns. The detector is read out in 4 quadrants, 8 channels per quadrant. An SAO-built controller is used to read out the array in a time of 0.7 seconds. Digitization is done with a 16 bit ADC, so data values up to 65,536 are recorded. Non-linearity sets in above ~40,000 ADU. The median dark current is 0.06e-/pix/sec.
There are two identical guide and wavefront sensing (GFWS) units mounted at the side of the instrument, external to the cryostat, which are fed by a fixed pick off mirror which surrounds the science beam. The field of the GWFS is shown in Figure 3. Each of the GWFS units is mounted on a 2-axis translation stage to allow it to probe one half of the available field and the cameras can be focussed individually. A stage allows switching between guiding and Shack-Hartmann mode; normal operation will have one of the units operating in guiding mode while the other is deriving continuous wavefront information. Slow-speed guiding information can also be derived from the Shack-Hartmann data which can be used to control the instrument rotation angle. In practice we have found it not to be necessary and is not part of the default operation. The guider optics operate from 600nm to 900nm as MMIRS will primarily be a bright-time instrument. The field of view of the guide camera is 80" with a pixel size of 0.16" (binned x2).
Figure 3 MMIRS field of view and coordinate systems. Full resolution PDF: p/mmirs_coordinate_axes.pdf
The origin of the instrument coordinate systems corresponds to pixel (1025,1037) on the science array. The center of the telescope rotator may differ from this instrument center by several arcseconds. The telescope rotation center will be determined at the start of each observing run by observatory personnel. When acquiring a new target, the telescope will first be pointed to place the target at the rotation center, and then offset to the instrument center.
A schematic representation of the status of all the instrument mechanisms can be seen in the toppermmirs display.
Figure 4 The toppermmirs display, showing the current status of the instrument. In this example the gatevalve is closed, as it would be during a slit mask exchange. The LEDs are used for calibrating the wavefront sensor and should normally be off, as they are shown here. Full resolution: p/toppermmirs.jpg
Prior to 2012B MMIRS has always been readout in 32-amp mode to achieve the fastest readout time (< 1 second). But at least 1 amplifier exhibits intermittent readout problems. MMIRS now supports a 4-amp readout mode that bypasses the problem amplifier - but also increases readout time to just under 7 seconds. See notes below about choosing the amp mode, appropriate exposure times and tables
The fitting algorithms underlying the alignbox application have been improved as follows:
For multi-slit mask users, a catalog will be automatically made for your mask targets and should be available on the operators computer once your masks have been loaded. For long slit users, you will need to specify a ROTATOR OFFSET angle in your Magellan format catalog. This angle should be your desired slit position angle times -1. For example for a slit aligned 20 degrees east of north, you would specify offset=-20. The rotator offset mode should be "OFF".
At Magellan you can place catalogs in your assigned observer account on the two observer workstations (Guanaco or Zorro) and the telescope operator can then copy it to the Operator computer (Vicuna)
The 3 MMIRS instrument computers are shack, wild, and hurley, but their consoles are located in the computer room. The observer will sit in front of the Magellan Mac computer guanaco and operate the instrument from the MMIRS computer wild from there. Data reduction can be carried out from the Magellan Mac zorro, by logging into shack or accessing the data directly on the cross-mounted disk at /Volumes/CRUNCH_MMIRS/. The hurley computer is dedicated to data acquisition and is not directly accessed by observers.
This will start the mmice interface.
Figure 5 MMice Quick Start tab.
A more deliberate startup sequence can be performed from the StartUp tab if QuickStart is unsuccessful. In general, this should only be necessary at the beginning of the run or after a power shutdown.
Figure 6 MMice startup tab. Full size image: p/mmice-Startup.jpg
On the mmice GUI in the Startup tab, press each of the following buttons and wait for the button to turn green.
Press Start Up MMIRS and the server status lights should turn green, as should the power status lights and all the device homed lights.
When the Startup initializations have been completed, the ideal configuration for the mmice window is for all the boxes on the startup tab to be colored green. There may be some cases when some parts of the system will need to be restarted during the course of the run. Go to the "Problem Solving" section to see how to debug if any of the status indicators are red.
In addition to mmice the following GUIs are used when observing with mmirs. They may be started or restarted from the Start/Stop page of mmice.
To log into shack or wild, type mmirsshack or mmirswild in any terminal on the observer workstations.
The directions which follow indicate how to deal with servers & devices which do not start cleanly during a instrument setup. If any of the status indicator boxes on the Startup tab are red (failed) or yellow (hung) this is the first place to start.
Figure 7 Mice Start/Stop tab. Full size image: p/mmice-StartStop.jpg
Data taking is done through the Config and ObserveOps tabs in mmice . The Config tab is used to set up the instrument as needed. The ObserveOps tab allows for traditional observing (one image at a time) or for performing sequences of exposures allowing for efficient observing. The sequences are defined by an ascii catalog file which can be generated with a text editor or by using the DitherTool tab of mmice . Details on how to make catalog files, with examples, are given in Appendix D.
In the previous section you should have gotten all the subsystems initialized. The status of each subsystem is indicated with color using the color convention of all the f/5 instruments; green means OK or RUNNING, yellow means HUNG (perhaps only temporarily), and red means NOT RUNNING. If any items are not green, go back to the Startup Procedures.
The middle section (just above the tabs) is mostly informational. The first line displays the detector and MOS dewar temperatures. The detector temperature should be 78.00 and the MOS temperature should be 77K. The second line shows the status of the calibration lamps. The rest of the lines in this section display exposure status information including image type, exposure time, and exposure status, sequence, queue status, instrument configuration and telescope offsets.
Figure 8 MMice status panel. Full size image: p/mmice-Status.jpg In this example we see that three servers are not running and two are hung. The recommended action would be to go to the Stop/Start page and restart them. Note that the telescope server will be started by the telescope operator at the beginning of the night.
Figure 9 MMice Config tab. Full size image: p/mmice-Config.jpg
TELNAME=clay_f5_ir INSTRNAME = mmirs DETNAME = mmirsIMPORTANT: For Science observations, make sure none of these indicates Test . For calibrations during the day where the telescope is not to be commanded, set TELNAME to 'test'. INSTRNAME should only be set to 'test' if you do not wish to move MMIRS devices.
The program number information is important to enter correctly in order to be able straight-forwardly retrieve data from SAO later on. If your observing program is not in the list, contact the MMIRS instrument specialist, who will get in contact with Maureen Conroy. If you switch programs during the night, don't forget to update the Observing Program and PI.
Figure 10 MMice ObserveOps tab. Full size image: p/mmice-ObserveOps.jpg
Manual means that all exposure parameters are directly set on this tab (although some software overrides may occur i.e. ObsType object will remove pickoff mirror). Catalog allows you to choose a catalog file that lists some or all of the parameters of a sequence of exposures. For example, you could have a list of dither positions to be observed in sequence. A full description of creating catalogs is provided in Appendix D. The file can be chosen by clicking on Menu.
Until the start of the 2012B MMIRS run, the MMIRS detector was always operated in the 32-amp mode giving the fastest readouts (less the 1 second). However, there have been persistent instabilities in one of the amplifiers. So to avoid this issue a new 4-amp readout mode as been added which doesn't use the problem amplifier. The trade-off is that the readout time is just under 7 seconds in 4-amp mode.
Select the amplifier mode you wish to use:
Select the type of exposure from the following list:
Table 2 MMIRS image types.
|object||A normal image containing an observing target. The file is named using the object name from the telescope catalog.|
|setup||Like object, but names the file "setup"|
|skyflat||A dark or twilight sky flat field image.|
|comp||A comparison lamp Argon image.|
|flat||A continuum lamp image. The bright lamp is used for spectroscopic exposures, the dim lamp for imaging.|
|dark||A dark image.|
Exposure time in seconds. Must be an integer number of seconds.
Select which mask or long slit you want, or "Open" for imaging.
Select which filter you want.
Select which grism you want, or "Open" for imaging.
Unlike CCDs, infrared detectors can be read out without destroying the image already stored. This has three key advantages. 1) By reading out multiple times, the detector read noise can be averaged down. 2) By reading multiple time during the course of the exposure, pixels can be used even if they are saturated by the end of the exposure. 3) Cosmic rays can be identified by looking for discontinuities in the signal level of each pixel versus time. The 'ReadTab' button is used to select the readout mode for the IR detector. The recommended modes are ramp_1sec, and ramp_5sec, and fowler. The first two read out the detector once every 1 or 5 seconds. The data will be stored as a multi-extension FITS file with one readout per extension. The post processing script will display the different of the last readout minus the first readout. If you select Fowler, or click on Cancel, you will get a simple double correlated image saved as a standard FITS file. This mode can be used for setup exposures.
Allows for manual telescope Az & El instrument offsets to be set (e.g. for dither steps)
This drop down box allows the user to choose one of several guiding modes. It controls how mmice interacts with the guider, but does not control whether guiding is turned on -- that is controlled from the telescope operator's "guistarsmmirs" panel.
Here is a description of these modes:
The Guiding row in the Exposure Status window will show YES or NO during "object" exposure, depending on whether the guide corrections are being sent. Flickers of a few seconds are common, but if the NO state persists it would be wise to consult with the telescope operator to verify that all is working well.
Default has it set as object name from catalogue through the telstat or set by exposure type being done.
The Clear button is used to clear the camera in the event of an error. If the Go button remains red because of an error during observing the user must press Clear to reset the system.
Pause. Abort, Resume.
The bottom 2 lines of the "ObserveOps" tab allow the user to "PAUSE" an exposure or to pause the QUEUE of exposures. "Pause Expo" enables the options: ABORT, STOP, RESUME, or CHANGE the exposure time. ABORT will discard the current exposure, whereas STOP will read out the camera for the current truncated exposure time. Pause QUEUE has no effect on the current exposure, but it allows you to alter the automated exposure sequence, usually by changing the "last" requested exposure. Because MMIRS has no shutter, it is not possible to actually pause and resume an exposure as one would with a camera with a shutter.
The raw images are stored on a 1.5 Tb disk on hurley, in multi-extension FITS format. A copy of each file is automatically made available for immediate analysis on shack. The analysis directories are called /data/crunch/MMIRS/yyyy.mmdd (e.g., /data/crunch/MMIRS/2009.1014). The files themselves will have names like target.0001.fits, where target is the catalog name supplied to the telescope. The /data/crunch/MMIRS disk from shack is also NFS mounted on the observer workstations as /Volumes/CRUNCH_MMIRS/. Since the instrument is operated from the observer workstation guanaco connected to the instrument computer wild, it is recommended that you do any additional data analysis from the observer workstation zorro; either directly using the cross-mounted /Volumes/CRUNCH_MMIRS/ or by logging into shack.
After an exposure is finished, the postproc server will receive the incoming image and display it in ds9mmirs Frame1 on the console. It will also display the difference of the current image and the previous one in Frame2. The usual iraf programs such as imexamine will still work. In fact you can have imexamine running continuously as new images come in and they will be properly accessed. Note: the appropriate IRAF analysis window running remotely from Wild should be started from any terminal on Guanaco with the command mmirsiraf.
The ds9mmirs window is intended to be dedicated to the near-realtime display. To look at previous images, we highly recommend working on shack and starting a local ds9 or running ds9 directly on zorro. To view previously displayed images, load them into ds9 using the File menu --> Open
As soon as the instrument specialist has completed the slit mask exchange procedure, take a test exposure to verify that the instrument is working properly.
cd /data/crunch/MMIRS/YYYY.MMDD imarith dark.MMMM.fits - dark.NNNN.fits diff.MMMM.fits imstat diff.MMMM.fits nclip=2 lsigma=3 usigma=3
The mean should be near zero. The stddev should be near 4.
There are no slit viewing optics in mmirs so to get your target on the slit you must take images with the infrared detector to position your target in the correct place. You will use both mmice and alignbox to accomplish this.
Ask the Telescope Operator to slew to your target from the observing catalog (and to offset to instrument center per normal operations)
In the mmicemmirs window, tab ObserveOps, select the following:
Figure 11 Longslit alignment tool. Full resolution image: p/alignbox-LongSlit.jpg
Now you are ready to take data.
After the exposure sequence on the target is complete, take a comp and flat
Follow the directions below for telluric standards.
An observing catalog generated from the mask design files is automatically generated on the day of a mask change. It can be found on shack as /data/archive/MMIRS/Masks-YYYY.MMDD.cat. It can also be found on guanaco in /Volumes/ARCHIVE_MMIRS, so that the telescope operator can copy it, although it should already be available on the operator computer in the catalogs folder.
Ask the Telescope Operator to slew to your target from the observing catalog (and to offset to instrument center per normal operations)
In the mmicemmirs window, tab ObserveOps, select the following:
Figure 12 Mask alignment tool. Full resolution: p/alignbox-MaskAlignment.jpg
If the mask file and mask image names do not appear - please notify the Instrument Specialist. You may generate them now using the Measure Mask button - but they should have been generated during the afternoon.
Now you are ready to take data.
After the exposure sequence on the target is complete, take a comp and flat
Follow the directions below for telluric standards.
Because the atmosphere has many strong absorption bands in the near IR it is necessary to observe standard stars at an airmass close to the airmass of your observations. An excellent description of telluric standards, can be found at http://www.gemini.edu/?q=node/10165 . A typical observing sequence would be to start by observing the telluric standard. Then observe your object till it transits, and go back to the telluric, and then resume your observations. Telluric standards with K=9 are appropriately bright.
The process for selecting telluric standards was developed by the FIRE spectrograph team, and is adapted here from the FIRE manual:
It is best practice to observe A0V telluric standard stars between science objects, to calibrate atmospheric absorption features. These observations are also used to perform flux calibration by the reduction software. There is a tool installed on guanaco and zorro which assists users in selecting tellurics from a large list of A0V standards. For each field required, run the following:
find_tellurics --RA 14:47:17 --DEC +04:01:12 --UO 08:50 --UT 09:25
The program, find_tellurics, takes the following inputs:
-RA, DEC - The right ascension and declination of your science target -UO - The central UT time of your science target observation (note this is the letter "O", not a zero) -UT - The expected UT central time of observation for the telluric standard
The software will output a list of stars which are the closest match in airmass and sky angle:
Object: RA= 14:47:17, Dec= +04:01:12 airmass= 1.372 at lst 16:43:14 Best telluric matches: (1): HD123309 ----- Magellan Catalog Number: 10215 Mag= 9.40 (Band= V) RA= 14:07:24 Dec= -23:28:29 Anguler Offset= 29.16 deg This telluric: airmass = 1.364 at lst 17:18:14 airmass diff from source = 0.007. Match rating = 54.18 (2): HD125062 ----- Magellan Catalog Number: 10249 Mag= 9.98 (Band= V) RA= 14:17:29 Dec= -19:29:07 Anguler Offset= 24.62 deg This telluric: airmass = 1.346 at lst 17:18:14 airmass diff from source = 0.025. Match rating = 30.37 (3): HD123426 ----- Magellan Catalog Number: 10217 Mag= 9.66 (Band= V) RA= 14:08:10 Dec= -24:33:51 Anguler Offset= 30.12 deg This telluric: airmass = 1.354 at lst 17:18:14 airmass diff from source = 0.018. Match rating = 27.47
The "Match rating" field is a figure of merit for the quality of telluric match, and should be as large as possible with maximum 100. Once you've selected from the list presented, the telescope operators have the catalog file of all MMIRS A0V calibrators available in MMIRS_tellurics.cat. It is a long list, so you should specify the star by its catalog object number rather than name. The object number is listed above in the field "Magellan Catalog Number." Note that the catalog orients the slit at the parallactic angle.
It is possible to acquire the telluric standard without removing the slit by using the guider.
The mask or longslit alignment process will generate a dither catalog that will offset the telescope to put the telluric standard on each slit of a mask if you follow this procedure.
Be sure to specify your science target dither catalog in mmicemmirs before proceeding with alignment. You will need to complete the alignbox procedure before you can do the science exposure sequence. You must take at least one alignment image with the mask inserted to do a Telluric sequence.
Be sure to specify both telluric and science dither catalog name in alignbox before aligning the slit. Then proceed with mmicemmirs to take the exposure sequences
If you are observing the telluric standard before observing with the mask or longslit you must first take an image of the mask or slit using alignboxmmirs before continuing. This will measure the exact location of the slit/mask.
Once the mask or longslit has been measured, or if you've just finished your science observations, then
After taking the telluric spectra, you can return to the target you were just observing without realigning by asking the telescope operator to "Return to the science target, and restore the offsets, por favor". Reset the mmicemmirs parameters:
Backup plan: If the telluric spectra do not appear, you may need to align the telluric manually. For longslits, follow the regular longslit alignment procedure, and then take spectra with the settings given above. For masks,
It is recommended to use guiding and wavefront sensing for imaging projects. The main role of guiding is to keep the wavefront sensor star going into the wavefront sensor.
The recommended maximum single exposure times for imaging are 45 sec for H and K and 300 sec for Y and J. At a minmum, you must remain at the same dither position for at least 15 seconds longer than the wavefront sensor exposure time (typically 30 seconds and not less than 15 seconds).
Using the ramp_5sec readout mode is also recommended for imaging as it will give you increased dynamic range on bright stars and reduced noise in Y and J imaging.
The best deep images are obtained if the dither pattern is random, rather than a square or line. You can read all about dither patterns on the Spitzer Science Center web site, here . A set of random dither patterns can be found on wild in /home/mmirs/Dither/Random. For example, random30.cat contains a set of dither patterns that fill a 30" box. To observer the same posiiton sequentially at each position in a 120" box, you would use random2x_120.cat.
At the end of the night you should take dark frames of every length of exposure that you took during the night. Fortunately you don't have to keep track of this yourself. Login into wild from guanaco by typing "mmirswild".
cd /data/ccd/MMIRS/YYYY.MMDD darkscript 5 Checking exposure times on all 379 files Please wait... 1. Go to Config page and set telescope to TEST 2. Go to the ObserveOps page and press Menu-->Darks-->darks-2011.1201 3. Press GO and watch the darks go!
On the morning of a mask change procedure, please do not start the dark script until the GateValve has been closed and the mask change procedure has been begun by the instrument specialist.
Please keep observing notes using the comment GUI which is started with mmirs. This will bring up a panel showing the fits files in the current data directory. You can highlight any one of the files and add comments to that log entry. To produce a nice postscript output click on View Log . The comments are archived along with the data and provide a valuable future reference.
Figure 13 Comment GUI.
At Magellan the data is cross-mounted onto Zorro for easy access. A USB/FireWire disk can be plugged into Zorro. The data can be copied directly using the Finder or from a unix shell. At the end of your run, Eject your disk using the Finder, and unplug it. NB: Data CANNOT be copied during observing operations. The additional load on network and disks will cause detector readouts to fail!
From zorro the archive data (updated the morning following the run) can be found in:
and the crunch data (where you may have some processed files) can be found in:
The filter transmission data in text format are available at http://www.cfa.harvard.edu/mmti/mmirs/instrstats.html MMIRS has two filter wheels, one top and one bottom, which can accommodate 5 filters each. Installing a new filter in MMIRS requires disassembly of the cryostat -- a major operation -- and cannot be done without advance planning. Contact Brian McLeod for more information.
The bias level in up-the-ramp data is typically 16000 ADU.
Please refer to the Exposure Time Calculator below for more estimates of background and counts expected at a given magnitude.
Many problems can be diagnosed using the mmice Status display. The top section shows the status of all the servers in the MMIRS client/server system. Green indicates that the server is up. Red indicates that the server is not running. Yellow indicates that the server is up but not responding. Sometimes servers will go yellow briefly if they are very busy. The servers are as follows:
This is the data acquisition server. If mmice fails to take an image, press the ccdmmirs button on the Start/Stop page. Problems with the array readout (weird patterns, all zeros), are also best dealt with by restarting the detector server.
This server provides information about the status of the telescope. Image header information comes from this server. If observe complains about no telescope information, set TELESCOPE=TEST on the Config tab. Don't forget to reset to the telname to mmt_f5 when the telescope is turned on or else your image headers will be missing information, dithering will fail, skyflats will fail!
The detector server for the guider camera.
Does the calculations for the guider.
The remaining items indicate the status of the instrument
If you are still having problems with mmice , and you can't get Mo or Brian on the phone, AND you are really REALLY desperate, it may be that someone changed something in the dommice code and now it won't work. As a last resort, you can invoke the previous version of mmice by typing "dooldmmice".
All problems (weather not withstanding), comments and suggestions should be reported. The best way to do this is to fill out the Astronomers section of the Daily Report, or in your Run Report, accessible under Forms at www.lco.cl. You can update the Daily Report any time during the night. Remember, if you don't report it, it can't be fixed!
For more information on MMIRS data reduction see:
Exposure Time Calculator
This calculator uses the information contained in the previous section.
DS9 templates for MMIRS are available in /home/mmirs/ds9templates, or can be downloaded here:
Save the downloaded files to a convenient location. Then in ds9 go to the Regions menu and select Template-->Load. Then just click in your image to put the template region on your image. To edit the center position and position angle, double click on the region. In the Composite window, select Coordinate-->WCS, and optionally Coordinate-->Sexagesimal. Then you can edit the position angle and center position.
Guide star availability can be checked by installing the MMIRS Mask Making software. Create a TAB DELIMITED file with a single ra/dec pair, e.g. tester.targets
ra dec -- --- 12:00:00 -37:00:00Then invoke the program as follows:
xfitmask tester tester.targets -check_boxes no -start_date XXXXThe GUI will appear and list all valid rotation angles. Note that a Magellan catalog file needs to have the sign of this position angle changed in the ROTATOR OFFSET column.
Rather than entering separate, time-consuming commands to do things such as change the filter, enter an exposure time, and type in an object name, the Catalog Ops refers to an established catalog to perform all those functions, and more. A series of exposures for a given target can be planned in advance and executed without astronomer intervention, in principle. Dither catalogs can be generated manually or with the DitherTool tab of mice.
The catalog can be very versatile as it allows you to offset the telescope, specify filters for each image, and specify exposure times for each image.
The catalogs are TAB delimited tables. Columns in the table are delimited by the TAB character. The first line contains the column names. The second contains dashes separated by tabs. See  for information on manipulating tables of this format. The available column names are
exptime The exposure time filts The filter name grism The grism name exptype object, comp, flat, or dark azoff The azimuth instrument offset eloff The elevation instrument offset readmode e.g. /home/mmirs/ReadMode/ramp_5sec.cat
Example dither files are located on (shack or wild) at:
/home/mmirs/Dither/XXX/*.cat in the following subdirectories: User Mask, Standard, Dark.
The following are commonly used dither files:
line3.cat 3 position diagonal dither that gets rid of the gaps
line5.cat 5 position diagonal dither that gets rid of the gaps
xyphotom.cat used for making photometric illumination correction
3x3.cat 3x3 pattern with 10 arcsec spacing
standards.cat run through filters and get standards in each; 1sec, 10sec and 100sec exposures
To list the offsets for a catalog use the following command:
column < line5.cat azoff eloff
You can of course create your own cat files in a text editor. However, the Dither Tool allows you to create cat files easily.
To use the dither tool, bring up the dithertool tab:
Figure 14 mice DitherTool tab. Full size image: p/mmice-DitherTool.jpg
The output of the dither tool is saved to a tab delimited text file which can be viewed or modified with any editor. Some examples of the output of the dither tool are shown below.
azoff eloff ----- ----- 0 0 48.2963 12.9409 -48.2963 -12.9409 96.5926 25.8818 -96.5926 -25.8818
The azoff, eloff columns give the offsets which need to be sent to the mount, i.e. the unrotated coordinate system. Note that the "eloff" values (elevation offsets), are offsets across the narrow dimension of the guide chips. So the default ordering is to sort by increasing absolute value of eloff as the best way to minimize the number of times that new guide stars have to be chosen.
filts exptime ----- ------- u,pol_45 300
A sequence of filters is delimited with spaces and will expand into a sequence of exposures. If a single exposure time is specified all the filters will use the same exposure time. Alternatively, a space-delimited list of exposure times can be specified as well and then the sequence of filters will be matched with the corresponding exposure time. To specify a filter sequence without dithering, the NoXpts or NoYpts entries must be blank.
filts exptime ----- ------- u 300 g 150 z 120
300s u, 150s g and a 120s z exposure would be taken. (As a reminder, there are tabs separating columns in the output table, but only spaces are allowed between entries in the GUI window. For instance, in the GUI entry boxes there is only a space between u g and z and also between 300 150 and 120.
If you create your own dither file it is important to verify that the formatting, especially the white space, is correct before using it. To verify the formatting type:
justify < filename.cat
which should produce the output neatly aligned in columns. Remember columns in the table must be separated by tabs.
Picture/Image Archive: p
Document Archive: d