2013-Jan 01
New year, new web pages
The NIRC2 web pages have been reformatted and reorganized to conform to the Keck instrument page standards. Feedback is welcome.
2012-Sep 18
NIRC2 cooldown starts
NIRC2 was opened up and serviced Sep. 17. The lead screw for the camera stage was inspected. The preload on the nut was reduced by removing one of the two wave washers. Testing when warm under vacuum showed that the stage was moving freely. NIRC2 is now closed up and has been vacuum pumped for 24 hrs. The cold heads have been turned on and cool down has started at 16:02 HST Sep. 18.
2012-Sep 10
Here comes the PIG
A new startup script has been released for NIRC2, which will automatically launch some of the most often used tools and GUIs, including the PIG (program identification gui). The PIG is a new tool that allows you to easily flag which data are yours on split nights. An example of the PIG is shown (for NIRSPEC; it is used for all instruments). A single click allows you to change OBSERVER names and data directory. An edit field allows you to change OBSERVER, if the default (from the telescope schedule) is not what you want. Please use the PIG while observing. It is your friend.
2012-Sep 08
Service mission initiated
We have decided to warm up NIRC2 in order to take advantage of an opportune window in the schedule this month to fix the camera stage problem that we've been experiencing. The CCRs were turned off around noon today. The dewar is expected to be ready to open for service Monday, 17 September. NIRC2 should be cooled and fully operational by Sep. 29.
2012-Sep 02
Camera stage difficulty
We have been experiencing some difficulty with moving the camera stage to the wide camera. As a precautionary measure, observers are strongly advised not to use the wide camera.We will attempt to trouble-shoot the problem when NIRC2 is off sky.
2012-Mar 23
Master flats and darks available
We now have a library of imaging flats and darks (some graciously provided by A. Kraus) available here. More can be added as they become available.
2012-Jan 01
More targets in the new year!
In the spirit of giving this holiday season, US Space Command recently increased the number of LGSAO targets that observers are permitted to submit for LGSAO observations. The new maximum per night is 130 total targets. For split nights, each half night observing team is allocated 65 targets.
2011-Sep 19
Service Mission Complete
NIRC2 has reached equilibrium operating temperatures. Cold head speeds are being tuned, but preliminary checks indicate that all systems are operating normally. More information on the newly installed filters is available on the updated filters page.
2011-Sep 07
Filters Installation Completed
NIRC2 was opened up and serviced Sep. 05-06. Seven new filters were installed: z, Y, L-wide, Pa-gamma, He IA (10,830A), Br-alpha, and Br-alpha continuum. The L-undersize and a duplicate Br-gamma filter were removed. The cold heads were purged. NIRC2 is now closed up and has been vacuum pumped for 24 hrs. The cold heads have been turned on and cool down has started at 16:07 HST Sep. 07.
2011-Aug 30
Service Mission Begins
Warm up of NIRC2 has begun for the service mission led by PI Keith Matthews to install new filters. An L filter, a Y filter, which was procured with generous partial funding from M. Liu, and a number of narrow-band filters will be added. The extra Br-gamma filter and the L-undersize filter will be removed. NIRC2 will be opened and filters installed Sep. 6-8. NIRC2 should be cooled and fully operational by Sep. 16.
2011-Jan 03
More Effient Data Acquisition Scripts Available
We have a new set of data acquisition scripts that improve on-sky observing efficiency by reducing delays in status checks and time waiting for data writing to complete. Some minor modifications were also made to quicklook to handle more rapid image exposures. The time saved by the new scripts is estimated to be about 15-45 minutes per night, depending on the nature of your program. Unfortunately, the new scripts have also been found to introduce a "side effect" that causes the detector (Alad) server to crash, on average, about once a night, which requires ~5 min to recover. We will continue to investigate these server crashes, but in the mean time if you wish to use the new scripts, please let your support astronomer know.
2010-Jun 17
NIRC2 Begins Full-Time VNC Operation
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Starting with the June 2010 NIRC2 run, we ask all observers to start up their NIRC2 control software within VNC desktops. Virtual Network Computing (VNC) is a technology that allows windows to be shared with observers at other computers and has been used successfully for years at Keck to provide mainland observers with access to Keck instrument controls. By expanding the use of VNC to all observers, we will thus have a single startup procedure for observers to follow regardless of whether or not they will operate with mainland observers. Operating under VNC also makes it easier for support staff to assist observers with troubleshooting and allows our observing assistants to monitor the status of observations during the night. Your support astronomer will be happy to assist you with starting your NIRC2 software under VNC. |
2010-Jun 09
Snappier Quicklook
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To take advantage of the color-map speed up available when quicklook is run from within an 8-bit display, the VNC configuration has been changed to use an 8-bit (tan background) display for the center screen. Users will also notice that xterms have all been converted to black-and-white to accomodate this change. The primary advantage of this change will be experienced when users apply right-mouse-button color stretch to tease out faint features. The improvement should help with rapid cadence programs such as companion-search survey programs. |
2010-Apr-23
MCDS Puzzle
We have discovered an unusual aspect of data collected with NIRC2 in
multiple correlated double-sampling (MCDS) mode. The peculiarity is
seen most easily in dark frames.
Figure 1 shows a
histogram, with the expected Gausian distribution, of pixel values
across a NIRC2 dark. The dark shown in figure 1 was taken in single
correlated double sampling (CDS) mode.
Figure 2 shows
a similar histogram of a dark taken in MCDS mode. Note the
excess of zero-valued pixels.
We have checked darks going back seven years, and with varying
numbers of samples, and we see the same effect in all these data.
Therefore, we believe that this phenomenon has existed since NIRC2
commissioned and occurs for all MCDS frames, regardless of the
number of samples sepcified. We will continue to look at this
problem to see if we can determine the root cause, and to see
if there is a significant effect on data quality resulting from
this anomaly.
2010-Apr-02
K Glow in Wide Camera
Users of the wide camera, observing at Kp (or longward of Kp), please
be aware that a 'glow' now appears in the lower right portion of the
detector. See jpeg image. The fits file associated
with this image can be downloaded by clicking here.
This effect began, we believe, around August, 2009, and may be the result
of a new optic that was installed on the AO bench (a replacement IR
dichroic) around that time. We are working to better characterize, and
hopefully correct, this effect. The effect produces a less than 1% increase
in flux in that area and may be removable by flat fielding.
2010-Feb 19
Keep it Linear
For observers who might be new to observing in the infrared: The harmful effects of over-exposing with NIRC2 are shown in figure 1. Note that, unlike a CCD (which will "flat top" if over-exposed), the correlated double sampling (CDS) mechanism inherent in IR readout systems, will result in a "roll over" phenomenon. In this example, the total DN reaches approximately 13000 at which point the measured signal begins decreasing.
2009-Sep 28
Filter curve data values are now available.
A spreadsheet containing the the data values for the passband curves that appear on the NIRC2 filters page is now available on that page. See Note #10.
2009-May 11
Dome flat instructions updated
Along with recommended integration times, the dome flat calibration instructions page has been update to include a step-by-step procedure. Please consult this procedure when taking flats unattended (e.g., morning dome flats).
2009-Jan 01
Fine pin-hole mask unavailable
Over the past 1-2 years, the NIRC2 slit stage has faulted on several occasions when driven to locations near its negative limit. For this reason, we are restricting use of that stage to exclude use of the fine pin-hole mask. All other positions for that mask (slits 10-through-160 for spectroscopy, coronagraphic spots 100 through 2000, and the coarse pin-hole mask) are available for use. We will continue to investigate this issue and apologize for the inconvenience.
2008-Nov 03
Fixed Pupil versus Vertical Angle Mode
Observers using vertical angle mode, who are intending a fixed pupil, for example users of aperture masking or angular differential imaging (ADI), should be aware that a tracking shift in the pupil plane of order 0.4 degrees occurs when an object being observed in vertical angle mode transits near zenith. This effect is likely related to the difference between true vertical and the as-built telescope Y axis, as the offset is equal to the difference between PARANG and PARANTEL. A correction equal to that difference must also be applied to recover absolute astrometry. This plot characterizes the jump.
2008-Jul 07
Transputer Board Replaced
A problem with the NIRC2 detector readout system occurred on Wednesday night, June 18th, 2008. The root cause was traced to a failed transputer board in the detector system electronics rack. That board has been replaced and since that repair mission, NIRC2 has been in use on five science nights without a recurrence of the problem. Several efforts are underway to improve our preparedness should a similar problem occur in the future, including the configuration of a hot-swappable host computer system.
2008-Apr 28:
IQ Repository Started
An Image Quality comparison page has been been generated for collecting observers' before and after experiences with NIRC2 since the upgrade of the AO Wave Front Controller.
2008-Apr 23:
LGSAO Differential Tracking Available (Shared Risk)
As of April 24, 2008, an LGS mode which allows for differential motion between the laser and the tip-tilt reference is available for shared risk. Limiting rates and magnitudes for this new mode, as well as all other nonsidereal AO modes, are provided in a summary table. Contact Randy or Al for details.
2008-Feb 23:
Astrometry Page Updated
The Astrometry Page has been revised, including new information related to the NIRC2 position angle.
2007-Oct 20:
Astrometric Calibration: M15 added
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The procedure for observing M15 for astrometric calibration
has been added to the
Astrometry Page. If you use the procedure, please consider contributing your calibration frames to the Observatory (via your Support Astronomer) for general use by the community. |
2007-Sep 12:
The answer is "14"
 |
Since the commissioning of NGWFC, many have wondered: Under what conditions is it better to use NGS over LGS? Please see KAON 489 figure 14 for details, but the short answer is "When brighter than 14th and closer than 10 arcseconds, use NGS." |
2007-Jul 17:
Dewarp Utilities Posted
The IDL code to remove geometric distortion (graciously provided by Brian Cameron) has been added to the NIRC2 web page. Go to the Dewarp Utility Page.
2007-Jun 4:
AO improved and characterized
Strehl-vs-magnitude and related performance statistics for the upgraded AO system have been characterized.
2007-Apr 4:
AO improved
The NIRC2 Adaptive Optics feed has been upgraded. Performance improvement is still being quantified, but in the mean time, check out this snapshot of improved performance at J from Mike Liu's April 3rd SSC presentation.
2007-Mar 26:
Astrometry discussed in Santa Cruz
At the CfAO Retreat held in Santa Cruz March 26th, an informal meeting was held by NIRC2 observers interested in precise astrometry. The collaboration has resulted in a report, recommended calibration fields, and a dewarp application. Once these are finalized they will appear on this page. In the mean time, email aconrad@keck.hawaii.edu if you desire preliminary versions of this material.
2007-Jan 17:
New Web Page in the Works
Please check out the new NIRC2 home page. It is a work in progress, but comments are welcome.
2004-July 28:
Zero Points updated
Based on photometric data gathered in April of 2004 the zero points have been updated. The values are included in the list of filters and in the NIRC2 manual. There was improvement in both the zero points and the background levels from the initial commissioning measurements, likely the result of cleaner optics on the AO bench.
2004-April 1: AO Enclosure has Silver Lining!
AO Rotator Optics (K Mirror) Recoated with Silver
The three mirrors in the AO rotator were recoated with silver (2 of the 3 surfaces were previously Al.) and reinstalled in March 04. The rotator, which is often referred to as the K mirror, was subsequently realigned to the optical axis of the telescope and to the pupil of the optical system. One requirement of the realignment effort was to minimize the pupil nutation as a function of rotator angle, which has been a significant problem in the past. The realignment effort met the requirements and was deemed successful with the pupil nutation now only 10cm on the primary (peak to valley). These changes will have several likely benefits to NIRC2 observers,
