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.


broadband zero point

The 2 read saturation limit of CHARIS in broadband mode is shown below. The average limiting magnitude is H = 8.5 mag.


Broadband Saturation Limit

NOTE: Throughput of SCExAO rebuild and AO performance on any particular night will affect these numbers. Strehl ratios of 60-80% were estimated when this data was taken