CHARIS is an IFS for the Subaru telescope. It sits behind the SCExAO coronagraphic and extreme AO system and AO188 adaptive optics systems at the Subaru telescope.

SPECIAL NOTE:

All zero point and saturation estimates were taken before the SCExAO rebuild during S16B. The nominal values have not varied significantly but are highly variable based on seeing conditions, extreme AO performance, and cloud cover. Suggested nominal CHARIS exposure times are listed for individual filters. The CHARIS operator should work with you to adjust these to nominal levels the keep the 99th percentil signal in the halo around the occulting mask just below the limits of nonlinearity or saturation (user preference). Suggested exposure times are defined for CHARIS receiving 100% of the NIR light.

 

When proposing to use CHARIS, please keep in mind that we share the light with the rest of SCExAO with several splitters:

Any of the following beamsplitters can be arbitrarily used (and changed) in real-time during a CHARIS observation

  1. Open band (AR Window): Current preferred method.
    • CHARIS receives 100% of the light
  2. 90:10 beamsplitter: Largely useful if the larger FOV direct imaging with CRED2 is desired in addition to spectra from CHARIS
    • 90% of the light is transmitted to CHARIS
    • 10% of the light is reflected to the infrared channel of SCExAO
  3. 10:90 beamsplitter:
    • 10% of the light is transmitted to CHARIS
    • 90% of the light is reflected to the infrared channel of SCExAO
  4. J-band longpass: Becoming new preferred mode. Testing is positive. Ask SCExAO operator before selection in place of AR window.
    • Everythign long of ~1.2 microns is transmitted to CHARIS, giving CHARIS it's full bandpass.
    • Everything short of ~1.2 microns is reflected to SCExAO infrared channel.
  5. H-band longpass:
    • Everything long of ~1.35 microns is transmitted to CHARIS for H,K,H+K band observations (in H-band, K-band, and broadband modes respectively)
    • Everything short of ~1.35 microns is reflected to SCExAO infrared channel.

Two additional notes:

  • Also please note that the internal ND3 filter in CHARIS is cold, but only functions in the low resolution (broadband) mode. It cannot be used in the high resolution mode.
  • When Observing in High Resolution K-band mode request the AO188 operator to remove the ADC.