CHARIS Sensitivity
NOTES:- The throughput of AO188/AO3k and SCExAO changed since this data was taken. In addition, AO performance on any particular night will affect these numbers. Strehl ratios of 60-80% were estimated when this data was taken.
- These results do not include the NIRWFS dichroic pickoff, or the NBS. These elements will reduce the throughput.
Broadband sensitivity
Suggested starting exposure times in broadband mode for an H-magnitude=5 is 25 seconds when observing with a coronagraph.
Note that there is a slight shift of the PSF off of the coronagraph occulter due to chromatic residuals in the AO188 ADC. Broadband mode must always have the ADC in (ADC-in is standard for AO188).
The estimated zero point of CHARIS in broadband mode is H = 18.7. This will yield 1 count/s/spectral channel.
Zero point estimation in Broadband mode.
The 2 read saturation limit of CHARIS in broadband mode is shown below. The average limiting magnitude is H = 8.5 mag.
Saturation limit in Broadband, without a coronagraph.
J sensitivity
Suggested starting exposure times in J-band mode for an H-magnitude=5 is 45 seconds when observing with a coronagraph.
The zero-point of each channel in J-band mode is given below, the max zero-point is J = 17.8 mag.
Zero point estimation in J-band mode.
The curve below shows the 2-read saturation limit with no coronagraph. The maximum allowable magnitude to avoid saturation is J = 7.2 mag.
Saturation limit in J-band, without a coronagraph.
H sensitivity
Suggested starting exposure times in H-band mode for an H-magnitude=5 is 45 seconds when observing with a coronagraph.
The zero-point of each channel in H-band mode is given below, the max zero-point is H = 17.4 mag.
Zero point estimation in H-band mode.
The curve below shows the 2-read saturation limit with no coronagraph. The maximum allowable magnitude to avoid saturation is H = 6.8 mag.
Saturation limit in H-band, without a coronagraph.
K sensitivity
Suggested starting exposure times in K-band mode for an H-magnitude=5 is 45 seconds when observing with a coronagraph.
The zero-point of each channel in K-band mode is given below, the max zero-point is K = 13.5 mag.
Zero point estimation in K-band mode.
The curve below shows the 2-read saturation limit with no coronagraph. The maximum allowable magnitude to avoid saturation is K = 5.5 mag.
Saturation limit in K-band, without a coronagraph.
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