Table of contents:
Zero Points Measurements Using Standards - Introduction
Standard stars are observed every photometric night with
WIRCam, on average 3 times per night for each of the J,H,Ks filters. Our
standards are picked from the UKIRT (FS) list. Except for engineering purposes
and for the sake of characterization, standards are not observed for
narrow-band filters (unless included in a PI program). Here, we use the four
well modeled spectrophotometric standards (CALSPEC models) and filter transmission
curves to determine the expected magnitude through narrow-band filters.
Measurements are made automatically based on the WCS in the
headers of the processed images and the known star position. Note that wide
band standards are generally observed with the telescope defocused by 0.5mm to
prevent saturation. FLUXBEST of SExtractor is used to obtain each measurement
in ADU on individual (not stacked) images.
The Zero Point vs. Date plots show the ZP after chip to chip offset
corrections for different observing runs (top X axis) and as a function of time
(bottom X axis - the day at the start of each observing run, since standard
stars started being observed). Each color represents a different standard star.
The Chip to Chip Offset histograms are made of a subsample of observations, i.e.
sequences where a star was positionned on each of the detectors within a few
minutes. The chip to chip offset for narrow-band filters shows a high spread
due to not enough measurements having been done. Use the corresponding
wide-band filter chip to chip offset.
last update: Fri Oct 17 10:48:17 HST 2008
Plots of WIRCam Zero Points and Chip to Chip Offsets
| FILTER |
Comment |
Zero Point vs. Date and Camera Run ID |
Chip to Chip Zero Point Offset |
| Y |
|
 |
 |
| J |
|
 |
 |
| H |
|
 |
 |
| Ks |
|
 |
 |
| LowOH1 |
|
 |
 |
| LowOH2 |
|
 |
 |
| CH4On |
|
 |
 |
| CH4Off |
|
 |
 |
| H2 |
|
 |
 |
| Kcont |
|
 |
 |
| BrG |
|
 |
 |
| |
Table of WIRCam Zero Points and Chip to Chip Offsets
# April 3 2007 - Loic Albert
# Created.
# July 27 2007 - Loic Albert
# Added one column, ZP_WONLC (Zero point without non-linearity correction) which gives the
# offset to apply to the zero point for data that has not been linearized.
# Added a VERSION column to tell which sets are used in different IIWI versions.
# August 16 2007 - Loic Albert
# Added entries for use with iiwi version 1.0 with non-linearity correction, but only valid for semesters 06B/07A. Will
# need to analyze 05B/06A standards to add their values to use with iiwi 1.0.
# February 26 2008 - Loic Albert
# Added the 08Aw01 data.
# April 3 2008 - Loic Albert
# Make ready for version 1.5 of `I`iwi.
# May 29 2008 - Loic Albert
# Modified to provide temporary ZP for the 08AW02 and 08AW03 runs.
# June 2 2008 - Loic Albert
# Updated for 08Aw01 to 08Aw03 runs.
# June 27 2008 - Loic Albert
# Updated temporarily to process standards of 08Aw04.
# September 11 2008 - Loic Albert
# Updated temporarily to include 08Bw02.
# October 15 2008 - Loic Albert
# Updated to include 08Bw03.
#
# This file tabulates the filter zero points and chip to chip zero point offsets. Here, the zero point is the Vega magnitude at which a flux of 1 ADU/sec is detected. The
# values are based on measurements of standard stars analyzed in the wircam_analyzestandard procedure. For chip to chip offset, the reference detector is chip #60 (extension 4).
# A jump in zero point occured when the WIRCam gain was changed from ~2.5e-/ADU to ~3.7e-/ADU (an exact factor of 1.5) in August 2006 but the reality is that, if expressed as
# the magnitude at which 1 e-/sec is detected, the "real" sensitivity of WIRCam has not changed. Note that the chip to chip offsets adopted for most narrow-band filters is that
# of its corresponding wide-band filter (e.g. H2, BRG and KCONT are that of KS), simply because not enough measurements exist for narrow-band filters. No noticeable trend of
# zero point with time has been observed so far with WIRCam. Flux measurements are made on fully processed single images using FLUXBEST of SExtractor.
#
#VERSIO STARTDATE ENDDATE FILTER ZP ZP_ERR ZP_WONLC ZP_EXT1 ZP_EXT1_ERR ZP_EXT2 ZP_EXT2_ERR ZP_EXT3 ZP_EXT3_ERR ZP_EXT4 ZP_EXT4_ERR COLTERM GAIN
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 Y 24.289 0.099 -0.000 +0.021 0.011 -0.144 0.009 -0.004 0.007 +0.000 0.011 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 J 24.120 0.040 -0.000 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 H 24.280 0.063 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 KS 23.552 0.049 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 LOWOH1 21.477 0.072 -0.000 +0.054 0.050 -0.109 0.053 -0.017 0.056 +0.000 0.033 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 LOWOH2 25.0 9.999 -0.000 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 CH4ON 23.167 0.053 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 CH4OFF 23.156 0.044 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 H2 20.999 0.078 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 KCONT 25.0 9.999 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
0.9.4 2005-11-01T00:00:01 2006-08-15T23:59:59 BRG 20.848 0.079 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
# Starting with semester 06B, the gain was changed x1.5 to 3.7 e-/adu
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 Y 23.820 0.099 -0.000 +0.021 0.011 -0.144 0.009 -0.004 0.007 +0.000 0.011 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 J 23.651 0.040 -0.000 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 H 23.811 0.063 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 KS 23.083 0.049 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 LOWOH1 21.008 0.072 -0.000 +0.054 0.050 -0.109 0.053 -0.017 0.056 +0.000 0.033 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 LOWOH2 25.0 9.999 -0.000 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 CH4ON 22.698 0.053 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 CH4OFF 22.687 0.044 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 H2 20.530 0.078 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 KCONT 25.0 9.999 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
0.9.4 2006-08-16T00:00:01 2007-08-31T23:59:59 BRG 20.379 0.079 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
#VERSIO STARTDATE ENDDATE FILTER ZP ZP_ERR ZP_WONLC ZP_EXT1 ZP_EXT1_ERR ZP_EXT2 ZP_EXT2_ERR ZP_EXT3 ZP_EXT3_ERR ZP_EXT4 ZP_EXT4_ERR COLTERM GAIN
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 Y 24.289 0.099 -0.000 +0.021 0.011 -0.144 0.009 -0.004 0.007 +0.000 0.011 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 J 24.120 0.040 -0.000 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 H 24.280 0.063 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 KS 23.552 0.049 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 LOWOH1 21.477 0.072 -0.000 +0.054 0.050 -0.109 0.053 -0.017 0.056 +0.000 0.033 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 LOWOH2 25.0 9.999 -0.000 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 CH4ON 23.167 0.053 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 CH4OFF 23.156 0.044 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 H2 20.999 0.078 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 KCONT 25.0 9.999 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
0.9.5 2005-11-01T00:00:01 2006-08-15T23:59:59 BRG 20.848 0.079 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 2.5
# Starting with semester 06B, the gain was changed x1.5 to 3.7 e-/adu
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 Y 23.820 0.099 -0.000 +0.021 0.011 -0.144 0.009 -0.004 0.007 +0.000 0.011 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 J 23.651 0.040 -0.010 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 H 23.811 0.063 -0.020 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 KS 23.083 0.049 -0.010 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 LOWOH1 21.008 0.072 -0.000 +0.054 0.050 -0.109 0.053 -0.017 0.056 +0.000 0.033 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 LOWOH2 25.0 9.999 -0.000 +0.027 0.021 -0.114 0.019 -0.013 0.015 -0.003 0.013 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 CH4ON 22.698 0.053 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 CH4OFF 22.687 0.044 -0.000 -0.001 0.053 -0.078 0.041 -0.039 0.052 -0.005 0.032 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 H2 20.530 0.078 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 KCONT 25.0 9.999 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
0.9.5 2006-08-16T00:00:01 2007-08-31T23:59:59 BRG 20.379 0.079 -0.000 +0.019 0.025 -0.060 0.023 -0.029 0.023 -0.001 0.017 0.0 3.7
#VERSIO STARTDATE ENDDATE FILTER ZP ZP_ERR ZP_WONLC ZP_EXT1 ZP_EXT1_ERR ZP_EXT2 ZP_EXT2_ERR ZP_EXT3 ZP_EXT3_ERR ZP_EXT4 ZP_EXT4_ERR COLTERM GAIN
# Starting with semester 06B, the gain was changed x1.5 to 3.7 e-/adu
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 Y 23.700 0.055 -0.000 +0.007 0.028 -0.142 0.022 -0.022 0.030 -0.007 0.019 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 J 23.668 0.050 -0.010 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 H 23.866 0.066 -0.020 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 KS 23.097 0.052 -0.010 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 LOWOH1 21.012 0.162 -0.000 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 LOWOH2 25.0 9.999 -0.000 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 CH4ON 22.713 0.042 -0.000 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 CH4OFF 22.680 0.042 -0.000 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 H2 20.520 0.069 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 KCONT 20.200 0.265 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
1.0 2006-08-16T00:00:01 2007-12-31T23:59:59 BRG 20.355 0.100 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
#VERSIO STARTDATE ENDDATE FILTER ZP ZP_ERR ZP_WONLC ZP_EXT1 ZP_EXT1_ERR ZP_EXT2 ZP_EXT2_ERR ZP_EXT3 ZP_EXT3_ERR ZP_EXT4 ZP_EXT4_ERR COLTERM GAIN
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 Y 23.864 0.028 -0.000 +0.007 0.028 -0.142 0.022 -0.022 0.030 -0.007 0.019 0.0 3.7 #measured on ext4 only
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 J 23.668 0.050 -0.010 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7 #no measurement
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 H 23.866 0.066 -0.020 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7 #no measurement
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 KS 23.097 0.052 -0.010 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7 #no measurement
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 LOWOH1 21.012 0.162 -0.000 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7 #not in
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 LOWOH2 25.0 9.999 -0.000 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7 #not in
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 CH4ON 22.743 0.035 -0.000 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7 #measured on ext4 only
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 CH4OFF 22.719 0.048 -0.000 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7 #measured on ext4 only
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 H2 20.568 0.023 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7 #measured on ext4 only
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 KCONT 20.200 0.265 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7 #not in
1.0 2008-02-16T00:00:01 2008-02-26T23:59:59 BRG 20.403 0.015 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7 #measured on ext4 only
#VERSIO STARTDATE ENDDATE FILTER ZP ZP_ERR ZP_WONLC ZP_EXT1 ZP_EXT1_ERR ZP_EXT2 ZP_EXT2_ERR ZP_EXT3 ZP_EXT3_ERR ZP_EXT4 ZP_EXT4_ERR COLTERM GAIN
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 Y 23.819 0.059 -0.000 +0.007 0.028 -0.142 0.022 -0.022 0.030 -0.007 0.019 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 J 23.726 0.040 -0.010 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 H 23.896 0.047 -0.020 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 KS 23.134 0.042 -0.010 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 LOWOH1 21.012 0.162 -0.000 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 LOWOH2 25.0 9.999 -0.000 +0.016 0.031 -0.114 0.026 -0.032 0.042 -0.005 0.021 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 CH4ON 22.775 0.041 -0.000 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 CH4OFF 22.750 0.052 -0.000 -0.02 0.04 -0.084 0.049 -0.05 0.04 -0.005 0.041 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 H2 20.600 0.047 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 KCONT 20.200 0.265 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
1.5 2008-02-16T00:00:01 2008-10-27T23:59:59 BRG 20.441 0.050 -0.000 +0.004 0.036 -0.061 0.027 -0.032 0.036 -0.001 0.022 0.0 3.7
| |
| 