DEIMOS News


New Reflective Multi-Long-Slit Mask Released (2008-Apr-28)
After several years of service, the popular LngVrMir mask has worn out and been replaced by a new and slightly different mask called LVMslits ("LVM" = "Long Variable Multi"). Like LngVrMir, this new mask features a reflective slit area and a series of 20-arcsec-long slits of various widths. Whereas the old mask offered 4 slit choices, the new mask has 5 (0.7, 0.8, 1.0, 1.2, and 1.5 arcsec). The LVMslits mask now appears in the default list of available masks on the DEIMOS run configuration form.

DEIMOS FAQ Page Upgraded (2008-Apr-21)
Tips and tricks on observing with DEIMOS have been added to the DEIMOS FAQ (frequently asked questions) page. Go there for those handy tips your friendly neighborhood support astronomer is always reminding you about!

DEIMOS Arcplots Widget Released (2008-Apr-06)
We are pleased to announce the initial release of the DEIMOS Arcplots widget, a GUI with which observers can generate arc line plots customized to any grating, central wavelength, and set of line lamps. This is useful for verifying the achieved wavelength range for specific slits. Please see the Arcplots Widget page for more information.

DEIMOS Mask Overlays Generating Tool Released (2008-Apr-05)
The new IDL routine dsim2regions can be used to help plot the locations of DEIMOS targets and slits on an image of the corresponding DEIMOS field. The routine reads information from the mask design files generated with DSIMULATOR and creates ds9 regions files which can be used to mark and label the locations of slits on an image with celestial coordinates encoded in the FITS header World Coordinate System keywords. Please see the dsim2regions page for further information.

DEIMOS grating slider 4 clamp-up problem (2007-Nov-03)
Grating slider 4 is unable to clamp up at certain DEIMOS rotator positions. This may indicate that some key components in the mechanism are worn and need replacement; however, we will not be able to complete that invasive work until after the November DEIMOS run. In the meantime, there are two things that observers can do if they experience problems switching to grating slider 4. The preferred option is to execute the new script called clampup_slider4, which will position the stage to a spot where it should be able to clamp up. If this fails, the fallback is to rotate the instrument by 90 degrees and try again to select the grating from the DEIMOS dashboard GUI. If this fails. try running clampup_slider4 at this new position angle.

DEIMOS imaging mirror replaced (2007-Jun-06)
The engineering-grade imaging mirror which has been used in DEIMOS since commissioning has been removed and replaced with the science-grade imaging mirror. The coating on the engineering-grade optic was in relatively poor condition due to tarnishing, but the new science-grade optic appears to be in outstanding condition (expecially considering that the coating is well over 5 years old). This change should increase the imaging throughput of DEIMOS when the mirror is used.

DEIMOS bias problems (2006-Dec-20)
Since the October 2006 earthquake, the DEIMOS science CCD mosaic has shown signs of low-level pattern noise and bias level variations which change from chip to chip. We have started troubleshooting the problem in partnership with experts at UCO/Lick Observatory and our preliminary finding is that the gain level on the science mosaic CCD controller has excess noise. Troubleshooting will continue in January 2007; until then, observers should expect somewhat higher noise in their images.

DEIMOS desktop changes (2006-Apr-22)
DEIMOS has become the first Keck instrument to change from the OLVWM window manager, no longer supported by Sun, to the FVWM window manager. A recent internal technical review concluded that FVWM was a preferred solution to alternatives such as GNOME and CDE. In addition to changing the window manager, we have also changed the way that observers will access instrument software: instead of using the window manager's pulldown menu, observers will now use the InstrMenu widget to run DEIMOS-related tasks. We welcome your feedback on these changes, which will soon migrate to the other Keck instruments.

DEIMOS computer and disk changes (2006-Apr-07)
The Sun Solaris E450 workstation which has run the DEIMOS user interface software since the commissioning in 2002 has been replaced by a more modern, faster SunFire V240. Also, the new DEIMOS machine (known as polo, like its predecessor) now features a Triton RAID-6 array offering nearly 2,000 GB of disk storage space. The new machine runs the DEIMOS software significantly faster than before, and with the new RAID array the time to write a full DEIMOS image to disk has decreased from 35 sec to 2 sec.

Update: Problem with science CCD mosaic amp 1B (2006-Mar-25)
Troubleshooting prior to the late March DEIMOS run failed to reproduce the amp 1B dropouts seen during the early March DEIMOS run. Until this problem resurfaces, observers are advised to return to using the default 2-amp readout mode for direct imaging.

DEIMOS motor controller failure (2006-Mar-21)
One of the two Galil motor controllers on DEIMOS failed during the downtime between the DEIMOS runs. The symptom of the failure was that the unit would not communicate and displayed a red FAULT lamp when powered on. We replaced the failed controller with a spare, which appeared to operate normally until we tried to move the grating select mechanism; all attempts to move the grating select stage resulted in motor shut off - positioning error. We replaced the failed spare with a new spare, which worked fine. All systems now operate normally.

Problem with science CCD mosaic amp 1B (2006-Mar-01)
The B amplifier on CCD 1 is occasionally failing to read out properly, resulting in lost data on this CCD. This amplifier is used when reading out all spectral images, plus direct images acquired in 2-amp mode. Until we resolve this problem, observers are advised to use 1-amp mode for direct image readout in order to avoid losing data. The controls for 1-amp and 2-amp mode can be accessed on the User Config panel from the main DEIMOS dashboard.

newday command now invoked automatically (2006-Mar-01)
It is no longer necessary for observers to execute the newday command to allocate new data directories and configure FCS files when starting up the instrument. The newday command is now invoked automatically when the instrument software is launched. This change allows the fcstrack script to write its logfile to the FCS subdirectory.

DEIMOS RAID array crash (2006-Feb-01)
The RAID-5 disk array which hosted most of the DEIMOS data directories has suffered physical damage and is now unreadable. Two of the 5 disks in the array were lost, preventing us from reading the data from the other disks.

Change in the operation of GO ZERO/GO BACK buttons (2006-Jan-27)
The logic controlling GO ZERO button (used to tilt the current DEIMOS grating to the zeroth-order imaging position) has changed. Until now, the logic has been to store the current grating tilt and restore to this value when GO BACK is pressed. We recently learned that this can cause problems if the GO ZERO button is pressed during a telescope slew: the instrument rotator will typically be slewing, and as a result the grating may be slightly out of position at the time the position is recorded. Hence, GO BACK ends up restoring the grating to the wrong position, which causes FCS to remain idle instead of tracking. The logic has now been changed so that when the GO ZERO button is pressed, if the actual and user-requested grating tilts are close but not the same, the requested position is the one to which the grating will return via GO BACK. If the actual position is not close to the demanded position, the GUI will generate an error message.

Gratings refuse to unclamp (2005-Dec-26)
DEIMOS is experiencing occasional problems with gratings refusing to unclamp when they have not been exercised for a few days. We believe this is because the air pressure that drives these pneumatic clamps bleeds off over time, leading to insufficient pressure to unclamp the grating. If this happens to you, see the troubleshooting guide for tips on fixing the problem.

FCS problems (2005-Dec-09)
Over the last 6 months, the DEIMOS flexure compensation system (FCS) has experienced intermittent problems with loss of signal from one of the two CCDs in the system (FCS CCD 1), causing the system to fail. The problems became more frequent during the November run, culminating in a hard failure on December 2 after which the system remained in a "fail" state. Working with personnel at Lick, we opened the FCS dewar electronics box and located a connector which was not well seated. The connector is now properly seated and the FCS functions normally. As part of the troubleshooting, Bob Kibrick at Lick developed new FCS control software which can function using only 1 of the 2 FCS CCDs. Although the flexure compensation in this mode will not be as good as when 2 CCDs are used, it will be much better than having no corrections at all. Please see the FCS troubleshooting notes for further information on using this script.

DEIMOS grating system repaired (2005-Aug-25)
The grating move problem reported in the April news item has now been eliminated. Working with a team from Lick, we disassembled the grating select mechanism and located two loose screws on slider 3. These were retightened and the system laboriously retuned (modified the GRATOFFx parameters) in order to allow all gratings to clamp up at all DEIMOS rotator positions.

DEIMOS collimator mirror recoated (2005-Aug-10)
The DEIMOS collimator mirror received the same beautiful Gemini silver coating as the DEIMOS tent mirror received in the spring, thanks to Maxime Boccas and his team at Gemini. New throughput measurements are pending. The shift in image position relative to the value prior to removal of the tent mirror is -7.8 px in CCD_X and -4.1 px in CCD_Y, which is within the 10 px requirement.

DEIMOS tent mirror recoated (2005-Apr-25)
The DEIMOS tent mirror received a beautiful new silver coating at the Gemini summit coating facility thanks to Maxime Boccas and his team at Gemini. New throughput measurements are pending. A side effect of the removal and reinstallation of the tent mirror is that the optical alignment has changed by a few pixels. This means that observers should not attempt to use FCS reference files generated prior this run, since it may be impossible for FCS to maintain alignment on such data.

DEIMOS grating move problems (2005-Apr-02)
The DEIMOS grating select stage experiences mechanical interference which causes grating moves to fail at certain orientations of the instrument. The problem is worst when DEIMOS is at a physical rotator position (in DEIMOS coordinates, as displayed on the Dashboards "Rotation" panel) of 270°, and occurs when trying to move slider 3 past the in-beam position. The symptom is that the grating select move fails at this point. The solution is to rotate the instrument by 90° either diection and re-try the failed grating move. When possible, avoid changing the grating when the instrument is near 270° rotator position.

DEIMOS tent mirror receives temporary coating (2005-Apr-02)
The DEIMOS tent mirror's protected silver coating has been degrading since installation, reducing the DEIMOS throughput. After the last run, we removed the optic, stripped the old coating, and replaced it with a temporary coating of bare Al to tide us over until we can recoat with a new protected silver coating in mid-April. A side effect of the removal and reinstallation of the tent mirror is that the optical alignment has changed by a few pixels. This means that observers should not attempt to use FCS reference files generated prior this run, since it may be impossible for FCS to maintain alignment on such data.

Offsets to guider coordinates removed (2004-Nov-03)
The slitmask mill was serviced in October and this appears to have restored the original zeropoint of the slitmask coordinate system. The offsets which were previously required to align stars on the guider are no longer needed.

deeplog command updated (2003-Oct-11)
The deeplog script will now print out information on only the latest N files if you supply a numeric argument.

Focus analysis script enhanced (2003-Oct-10)
The Analyze Focus script will now set the DEIMOS focus to the newly-determined value if you consent.

Re-arrange your GUIs automatically (2004-Oct-09)
With one click, you can now resize and move all of the DEIMOS GUI windows into their appropriate configuration. Simply go to the OpenWindows pulldown menu, select DEIMOS Utilities > Auto-arrange GUIs, and watch your windows morph into place!

Offsets to guider coordinates (2004-Sep-14)
Several observing teams report that the guider appears to have shifted, resulting in a 10-column offset between the predicted and actual positions of the stars in the guider when the mask is aligned. Observers should thus apply a +10 pixel offset to the intended x coordinates of their guide stars when completing the coarse phase of slitmask alignment; i.e., instead of typing 
	gmov 100 200 300 400
type 
	gmov 100 200 310 400

Several DEIMOS filters damaged (2004-Jun-23)
An unfortunate incident this spring has resulted in significant damage to several of the DEIMOS filters. The affected filters are:
  • V filter for direct imaging
  • BAL12 filter for spectroscopy without an order blocker
  • NB8580 filter for spectroscopy of the Calcium triplet
The damage was caused by a bent component in the filter wheel which grazed the surface of the filters when the optics were inserted or removed from the instrument. The scratches run along the center of the filters (covering less than 5% of the surface area) and are oriented in the spectral (not spatial) direction when the filter is in the beam. Plans for replacing the filters are on hold until we can establish the level of degredation to their performance. In the meantime, observers who would normally have used BAL12 for spectroscopy are advised to use the GG400 filter instead. Since DEIMOS transmits very little light below 4000 Å anyway, we do not expect a significant impact on observing.

FCS now runs automatically (2004-Mar-25)
The DEIMOS startup and shutdown scripts have been changed to launch the FCSTRACK script automatically, eliminating the need to perform the additional step of running FCSTRACK frm the pulldown menu during afternoon setup. Please be aware that if the DEIMOS software is shutdown and restarted, FCSTRACK will probably come up in its default (idle) configuration. Click the START button on the FCS GUI to re-enable FCS tracking.

Subtle problem with BLANK pixels (2003-Nov-21)
DEIMOS images taken between October 2002 and November 2003 are affected by a newly-discovered problem with certain data values. The problem is subtle and may be unnoticable for many observers. A full description of the problem and the simple solution is now available courtesy of Steve Allen (UCO/Lick).

spec2d version 1.1.4 released (2003-Sep-23)
The DEEP Survey team at UCB announces the release of a new version of the spec2d reduction package. Please see the release notes for full information, and consult the pipeline website for info on how to update your copy of spec2d. In addition to the revised version of the code, there are new calibration frames available; please click here for details. It is strongly recommended that all 2003 data be rerun with this new set of calibration files. Please note that an email list has been established to notify interested parties of developments related to spec2d. Email sent to this address will be directed to everyone on the spec2d_users subscription list which includes the developers here at UCB. Please contact to be added to the email alias.

AUTOPANE saves readout time (2003-Aug-25)
DEIMOS will now read out direct images and mask alignment frames faster, thanks to the new AUTOPANE keyword. When AUTOPANE is set to AlignArea (the ne default), the CCD system will readout only the illuminated rows if a direct image (without slitmask) is taken, and only those rows containing the alignment boxes if a slitmask alignment image is acquired. Spectral exposures are read out in full, as previously. Observers can control the setting og AUTOPANE using a new selector on the User Config panel of the DEIMOS Dashboard. For more information, please see this document.

DEIMOS Update (2003-Aug-07)

Use guidermon to detect guiding problems (2003-Jun-03)
The new guidermon script will monitor the guider signal-to-noise ratio (S/N) and generate an audio alarm if the S/N falls below the minimum threshold you specify. It can thus be used to detect the onset of cloudy weather and allow you to pause an exposure before it is degraded by clouds, or to be warned if the guide star wanders out of the guide box for some other reason. Once the signal has fallen below the threshold, the software will continue to monitor the guider S/N and will generate a different audio message when the guider counts exceed the threshold again. To use this script, open a local window on any machine in Remote Ops and type: 
	guidermon thresh
where thresh is the threshold at which to generate warnings. The appropriate value of the thresh parameter will depend on the brightness of the guider star and the guider integration time. A reasonable value would be 50% of the starting S/N.

Enhancements to DEIMOS IRAF package (2003-Jun-03)
The IRAF package keck.deimos has been modified to make observing with DEIMOS easier. The following tasks are affected:
  • cdata. This new task will take you to the current data directory for DEIMOS, just as the corresponding cdata alias does on polo.
  • do_xbox. Previously, this task had been constructed to run xbox on the next image to be read out; it you wanted to analyze an existing image you had to run xbox instead. The task has now been modified such that if a new image is currently being taken or reading out, the task will wait for it to complete and then analyze it. But if no image is in progress, it will simply analyze the most recent image. In most cases this is the desired behavior anyway.
  • get_seeing. If you issue the command get_seeing last, the task will now analyze the most recent image.

"apropos" command for DEIMOS scripts (2003-May-29)
DEIMOS has a sizeable library of user scripts which can be used to control the instrument. You can now use the new apropos command on polo to search for commands related to a certain keyword.

DEIMOS slitmask imaging widget (2003-May-28)
Observers should acquire a direct image of each of their slitmasks in the afternoon and run xbox on them to verify that they function as expected. Observers can now use the DEIMOS Slitmask Imaging Tool to acquire these data rapidly and conveniently.

spec2d version 1.1.3 released (2003-May-20)
The DEEP Survey team at UCB announces the release of a new version of the spec2d reduction package. Please see the release notes for full information, and consult the pipeline website for info on how to update your copy of spec2d. The new version includes a patch for a noteworthy bug which affects all masks milled after the middle of October, 2002. The release notes provide the details of this bug, but it is important to note that all post-October masks need to be rerun using v1_1_3!

Generating DEIMOS slitmask maps (2003-May-03)
The DSIMULATOR slitmask design package can generate an optional plotfile which consist of Lick MONGO plot commands; however, few people have access to this software package. For the convenience of observers, a new IRAF task will accept the DSIMULATOR plotfile as input and will generate a plot using the STSDAS.IGI plotting program. You can download this script and run it at your home institution, or bring your DSIMULATOR files to Keck and generate the maps here.

Generating DEIMOS guider finder charts (2003-May-02)
Dan Magee (UCO/Lick) has generously donated a wonderful software package which generates nice DEIMOS guider finder charts using the Digitized Sky Survey and the output files from DSIMULATOR.

Experimental ds9 released (2003-Apr-24)
A new, "experimental" version of the ds9 image display tool is now in use for DEIMOS observing. This version features two new ways to compute image statistics, accessible under the Analysis menu:
  • Simple stats is a barebones widget allowing one to compute basic statistics on one image region.
  • Advanced stats is a full-featured widget with options allowing simultaneous calculation of statistics on multiple regions.

Zeroth order imaging available on slider 4 (2003-Apr-24)
The staff of Keck and Lick Osbervatory recently completed mechanical modifications to increase the range of motion on slider 4, allowing it to reach the zeroth-order imaging position. Observers can now perform slitmask acquisition and MIRA on slider 4. Various user scripts which involve zeroth order imaging have been updated to reflect the new capability, including gozero, image_user_masks, and align_check

New script aids afternoon setup (2003-Apr-24)
Observers should acquire a direct image of each of their slitmasks in the afternoon and run xbox on them to verify that they function as expected. To speed the process of acquiring the direct images, observers can use the new image_user_masks script. By default, it will reconfigure DEIMOS for direct imaging on the current slider and acquire images of all user masks. To image only certain masks, list their names as arguments. The slitmask checklist has been updated to describe the use of this script.

spec2d version 1.1.2 released (2003-Apr-16)
The DEEP survey team at UC-Berkeley announces the release of version 1.1.2 of their IDL-based DEIMOS data reduction pipeline sofwtare. Known as spec2d, this software takes an input a set of undithered DEIMOS spectral exposures and produces a set of individual, sky-subtracted 2-D spectra for each slitlet. Please see the description of the spec2d software pipeline for further information on obtaining and using the software.

DVD writer available (2003-Mar-30)
DEIMOS observers can now write their data to DVD (or CD) using our automated writer and software. The observatory provides both the media and a GUI for completing the writing. Each DVD can hold 4.7 GB of raw data, so it is generally possible to store a run's worth of data on a few discs. To access the GUI from any instrument account, select Instrument Utilities > Autobackup from the OpenWindows workspace menu.

FCS software upgraded (2003-Mar-25)
Three components of the FCS software have been upgraded:
  1. The FCS keyword library (service deifcs)
    All FCS-related keywords have been moved into the deifcs service. Previously, some FCS keywords (e.g., FCSMODE, FCSMSG) were contained within the science mosaic keyword library (service deiccd). Many new keywords have been added, providing access to the individual measurements computed for each FCS CCD. The FCSRMXxx keywords provide measurements of the FCS system's RMS tracking error during each science exposure. These new keywords are recorded in the FITS headers to provide a record of how well FCS was able to stabilize each science exposure. Note: the FCSCORRX and FCSCORRY keywords have been replaced by the FCSCORXM and FCSCORYM keywords, respectively.
  2. The FCS GUI
    The FCS graphical user interface has been completely re-worked. It provides many new features, including user-adjustable plot scales for various plots of the FCS tracking performance. Status displays provide detailed information regarding various warning and lockout conditions, and pop-up alarms notify the observer of any conditions that would degrade FCS tracking performance. The new GUI also provides features for taking FCS reference images.
  3. The fcstrack script
    The fcstrack script has been significantly upgraded to support the new capabilities of the FCS GUI. The revised correction algorithm provides improved image stabilization, especially when DEIMOS is rotating at higher velocities as occur when tracking objects near the keyhole. The revised algorithm also provides more robust handling of cosmic ray events; previously, such events would sometimes result in spurious FCS corrections.
Both the FCS Startup Checklist and the FCS Notes have been updated to reflect the changes.

FCS upgrade reduces scattered light (2003-Mar-02)
A recent upgrade to the flexure compensation system by Lick and CARA added hardware which turns the FCS lamp on only during an FCS exposure; previously, it was always on when FCS was running. Since FCS integrates for only a few seconds on each iteration, this should reduce the amount of scattered FCS light on the detector by a factor of 3 more.

Observing preparation checklist published (2003-Jan-31)
The new DEIMOS Observing Preparation Checklist tells you the things you need to know to prepare for your DEIMOS slitmask observing run and points out some key resources you should bring along.

Slitmask calibration widget released (2003-Jan-31)
The new Slitmask Calibration Widget automates the process of acquiring calibration data (arcs and internal flats) for a series of DEIMOS slitmasks. See these instructions on its use.

DEIMOS Update (2003-Jan-09)

Filter focus discipline released (2003-Jan-08)
De Clarke of Lick has written new software which will automatically adjust the focus of DEIMOS to compensate for the difference in focus values between the various DEIMOS science filters. The software takes as parameters a global shift in focus (derived from daily focus checks in the R band which you should run in the afternoon) and focus offsets for each filter relative to the R band. The DEIMOS focus is adjusted each time a filter is changed, with the changes being "invisible" to the observer.

New deeplog utility generates electronic logsheets (2003-Jan-08)
The new deeplog utility allows you to generate a listing of the images in your data directory to complement or replace your paper logsheets. The text output produced by the script isn't pretty but has the key benefit of being machine readable. See some sample output.

Flexure compensation centroiding improved (2003-Jan-01)
Bob Kibrick and Drew Phillips of Lick have developed a new cross-correlation algorithm for the DEIMOS flexure compensation system that simplifies the afternoon setup procedure and is far less prone to losing its "lock" during the night. The new algorithm is now the default and has performed perfectly since being deployed in late December.

Ghosting seen in 900-line grating (2002-Oct-22)
Drew Phillips has written a nice report on unusual ghosting seen when using the 900-line grating on DEIMOS. Until further notice, observers should use dome flats only for the 900-line grating, and other gratings that work at a similar tilt. Observers should be aware of the problem and watch for it in their data.

DEIMOS Update (2002-Oct-17)

DEIMOS slitmask design software released (2002-Aug-09)
Drew Phillips (UCO/Lick) has announced the initial release of his IRAF-based software package for design of DEIMOS slitmasks. Details on the installation and use of his software may be found at his website.
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Last modified: Thu May 15 15:03:25 HST 2008