Proposal methods

CHARA offers two methods of applying for time. Consortium members may propose through an internal annual call for proposals. This process is advertised on the CHARA mailing list and typically has a deadline in mid-February.

Non-consortium members may request time through community access time manged by the National Optical Astronomy Observatory. At present about 50 hours have been pre-allocated to this program for the entire 2015 calendar year. Please note that the 2015A proposal cycle (deadline Sept. 25 2015) covers all of the 2015 calendar year. CHARA cannot guarantee productive observations, but is prepared to devote more telescope time than the allocated total in order to increase the odds of success. Community access observations will be carried out by CHARA staff. Visitors are welcome to travel to the array; however, observation dates may not adhere to an advance schedule. Consortium members will support data reduction to Optical Interferometry FITS format, although most users find it interesting (and not that difficult) to run the reduction software themselves. Information about the data reduction pipelines can be found on the data reduction and individual instrument pages. Modeling and image reconstruction software may be found in the data analysis section of this website, the Exoplanet Science Institute, and the Jean-Marie Mariotti Center.

CHARA capabilities

The CHARA array is applicable to problems in almost all areas of contemporary astronomy. It is particularly suited to stellar astrophysics where it will be used to measure the diameters, distances, masses, and luminosities of stars as well as to image features such as spots and flares on their surfaces. Other science topics have included detecting other planetary systems, imaging stars in process of formation, and studies of bright transient phenomena like novae.

All objects observed must satisfy all magnitude requirements for acquisition, tracking, and beam combination listed in the table below. At present, CHARA has no off-axis guiding capabilities.

ModeTelescopesBandTypical limit Mag=Best performance Mag=At Spectral Resolution R=
Acquisition 2 V-R 10.0 12.0 Broad band
Tilt tracking 2 V-R 10.0 12.0 Broad band
CLASSIC 2 H or K band 7.0 8.5 Broad band
CLIMB 3 H or K band 6.0 7.0 Broad band
VEGA (hi-res) 2 or 3 2 bands of 7nm (separation 30nm) in 480-850nm 4.0 5.0 30000
VEGA (med-res) 2 or 3 2 bands of 35nm (separation 160nm) in 480-850nm 6.5 7.5 6000
MIRC 6 H 4.5 5.5 40
PAVO 2 630-900 nm 7.0 8.0 30
JouFLU 2 K band 4.5 5.0 Broadband

Time required for one observation

A single interferometric “snapshot” is often taken in a calibrator-science-calibrator sequence. This process requires ~30-90 minutes. Each observation may produce between one to several dozen UV points, depending on the instrument. This amount of data can determine, for example, an angular diameter, a limb darkening strength, a binary separation, or the fraction of emission in a shell. More complex tasks like time variable studies or imaging complex sources typically require larger time allocation.

Proposal tools

Observations may be planned using either the chara_plan2 software distributed with the CLASSIC/CLIMB data reduction software or usingAspro2 from the JMMC. Interferometric calibrators may be found usingSearchCal or getCal.