The CLASSIC and CLIMB beam combiners of the CHARA Array are open air, aperture plane, broadband, single spectral channel instruments optimized for sensitivity. CLASSIC is the original two beam combiner used for the first science at CHARA, and it still has the faintest magnitude limit. CLIMB is a three beam expansion of CLASSIC that also provides closure phase measurements.

CLASSIC and CLIMB typically operate in the near-infrared H (1.6731 μm center, 0.2854 μm width) and K' (2.1329 μm center, 0.3489 μm width) bands.  Observations are possible in the J-band (1.286 μm), but the magnitude limit is lower compared with the H and K' bands.

The CLASSIC and CLIMB combiners were built by Georgia State University.

Light paths for the CLASSIC (green) and CLIMB (red) combiners.


Observing and Data Reduction

CLASSIC/CLIMB Observing Manual.

The CLASSIC / CLIMB data reduction software was written by Theo ten Brummelaar.  It is recommended that the code is run using the michelson computer on the mountain or using the Remote Data Reduction machine through the CHARA server in Atlanta.  These computers will have the most recent versions of the code installed.  The reduction software is maintained through the CHARA gitlab repository.  A compiled version of the software is usually available for download on Theo's website.  However, this static copy does not always include the most up-to-date version of the code, so it is recommended that the software is run from one of the CHARA computers.

The current pipeline for CLASSIC data is redfluor.  The pipeline for CLIMB data is redclimb.  John Monnier has an independent reduction pipeline for CLIMB that is written in IDL.

Tutorial on reducing CLASSIC data using the redfluor pipeline.

Tutorial on reducing CLIMB data using John Monnier's IDL pipeline.  The tutorial was written by Kathryn Lester.


Technical Reports

The CLASSIC/CLIMB Data Reduction: The Math - Theo ten Brummelaar

The CLASSIC/CLIMB Data Reduction: The Software - Theo ten Brummelaar

Using the Mean Power Spectrum to Compute the Visibility with REDFLUOR - Gail Schaefer

CLASSIC J-Band Calibration -  Schaefer, ten Brummelaar, Farrington, Sturmann, Anderson, Majoinen, & Vargas


Instrument Paper

The CLASSIC/CLIMB Beam Combiner at the CHARA Array -  ten Brummelaar, T.A., et al. 2013, JAI, 2, 1340004 (pdf)