MOIRCS Instrument Parameters

Detectors and readout ElectronicsHAWAII-2RG Science Grade x 2
Sci#16926 (channel 1) and Sci#16843 (Channel 2)
SIDECAR ASIC: #40 (channel 1) and #39 (channel 2)
Pixel size18 um
Pixel scale(1)0.116''
Field of view3.9' x 6.9' (2)
Gain(3)2.07 e-/ADU (ch1), 1.99 e-/ADU (ch2)
Dark current< 0.005 e-/s
Saturation level~33k ADU (4)
Read noise17.5 e-(5)
Number of amplifiers per detector32
Minimum Exposure (sec)1.475*NDR (NDR=1 for normal CDS data)
Overhead of repeated readout(6)~12.5+1.475*NDR (sec)
Filter exchange time 15~60 sec
MOS
Number of available mask slotsup to 21 (16 for users)
Typical number of slits per mask40~60, depending on the length of the slitlets(7) and target layout
Days needed for cooling mask 2 whole days
MOS aquisition time(8) about 20 min

(1) The value is measured around the center of the raw image. Note that the pixel scale becomes smaller with the distance from the optical axis (near the image center) due to distortion.

(2) Hawaii-2RG detector has 2040 x 2040 sensitive pixels, with the additional 4 rows and columns of "reference pixels" on each side (see Detector Information). An about 0.4 arcmin2 region at the upper right of the channel-2 raw image is vignetted by the Cal Probe Box on telescope. Please see the FOV page. And also, the mosaic boundary between channels (~0.4 arcmin2) is not usable for science.

(3) Measured values in April 2016 using the final Readout Parameters setting by the photon transfer method (with the ~6% inter-pixel crosstalk correction). Though the nominal error is 1%, more systematics may exist.

(4) Actual saturation level devends on the intensity of the input light. In H-band it would be as low as 25k ADU, while in NB it would be well over 30k ADU. Note that the ~5% non-linearity level is much shallower than saturation level. We recommend keeping the maximum counts of the data after CDS less than 22000 ADU.

(5) Under the single CDS (NDR=1). The value under the multi-sampling (NDR) reduces the noise by sqrt (NDR), though the reduction somewhat slows down at NDR > 10 (1.1-1.3 times larger than sqrt(N) estimate).

(6) Typical value with a few seconds of variation. Note that the value does not include the time related to the telescope move. See the Overhead Part in the "Guide to exposure time" webpage for more.

(7) Assuming the use of 7".5-length slitlets. See the MOS section for more about the choice of slit length.

(8) See also the MOS page. The acquisition time for Long slits can be similar or a bit shorter than this.



FITS file format and Header Keywords

We use the Multi-Extension FITS (MEF) format since 2016. The Primary FITS data and the header are for the CDS data you will use for your science. Extension 1 is the "reset level (or "pedestal") image", i.e., the image just after the reset, and Extension 2 is the "signal image", the image after the exposure time. The CDS frame is made by, 1) subtracting the reset level data from the signal level data, then 2) subtracting the bias level using the "reference pixel" regions. If you use the multi-sampling readout, the same number of reset level images and signal level images as multi-sampling number is attached. See also the "Detector information" Page for more.

For the fits information for the old moircs, please visit the old page below.


Old MOIRCS Information

The old (before 2015) MOIRCS information page can be found here.



Please note that all data on these pages are subject to change as the evaluation of the performance of the upgraded MOIRCS progresses.

Updated 2023-02-05


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