NIRC2 Calibrated Data
Introduction
NIRC2 calibrated data are available for imaging mode only. Spectroscopic data are currently not offered in calibrated form. When the appropriate calibration files are not available or otherwise cannot be found, no data processing is performed. A description of how calibration files are matched with science files can be found in our NIRC2 calibration association document.
Each science file is calibrated separately as follows. First, bad pixels are corrected by applying a master bad pixel map and replacing each affected pixel count by the median of the surrounding pixels. Then the data are subtracted by an appropriate dark frame (if one exists) and divided by a flat. Flats and darks are produced from median combining a number of images, mainly for the broadband filters and the narrow camera. If available, a master flat and/or dark is used. If not, the median of a maximum of 10 flats and/or darks found by the calibration association will be used. Finally, if full-frame (i.e., 1024x1024 pixels), the image is corrected for optical distortion following the prescription described on the NIRC2 astrometry utility page, using B. Cameron's IDL routine. Note that the last step, distortion correction, is not performed for sub-arrayed images. Also, as part of preparing NIRC2 data for archiving, world coordinate system (WCS) information has been added to the image FITS header.
NIRC2 calibrated data are produced by an automated pipeline and intended mainly for browsing purposes only, and may not be of publishable quality. In particular, no sky-subtraction or data stacking of dithered images has been performed. For high-quality scientific use, users are recommended to download the raw science and calibration files and reduce the data themselves.
Directory Structure
When the user chooses to include the calibrated images, the resulting packages will contain two subdirectories: "raw" containing the raw data files and "calibrated" containing the calibrated data files.
Calibrated Image Visualizer
In addition to the normal JPEG preview image, NIRC2 calibrated data can be examined using an interactive visualizer. This visualizer allows the user to modify the color table and intensity stretch, overlay a coordinate grid or compass rose, examine the full FITS header, and zoom in on particular regions of interest. More information about the visualizer is available as embedded help in the application or in a short video.Please acknowledge the use of KOA by including this text in your publications:
This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration.
Please also acknowledge the PI(s) of datasets that have been obtained through KOA, and please contact the KOA Help Desk if you publish archival data.
If your research uses data reduced by the DEIMOS DRP or MOSFIRE DRP, please use the PypeIt Citation.
Privacy Policy Image Use Policy
The Keck Observatory Archive (KOA) is a collaboration between the NASA Exoplanet Science Institute (NExScI) and the W. M. Keck Observatory (WMKO). NExScI is sponsored by NASA's Exoplanet Exploration Program, and operated by the California Institute of Technology in coordination with the Jet Propulsion Laboratory (JPL).
