DECal is a spectrophotometric calibration system that will be
implemented as part of the DES DECam project at the Blanco 4 meter at CTIO. The system
uses a 2nm wide tunable source to measure the instrumental response function of the
telescope from 300nm up to 1100nm. This calibration will be performed regularly to
monitor any change in the transmission function. The system consists of a monochromator
based tunable light source that provides illumination on
a dome flat that is monitored by calibrated photodiodes and allow us
to measure the throughput as a function of wavelength. Our system has
an output power of 2 mW, equivalent to a flux of approximately 800
photons/s/pixel on DECam. We successfully deployed a prototype of
this system at the Swope and DuPont telescopes at Las Campanas
Observatory. This provided data to help reduce the systematic error
budget of the Carnegie Supernova Project.
Layout for the DES Calibration Project
J-P Rheault working on the Screen for DECal.
This will be an upgrade to the current screen at the Blanco telescope. It is
coated with a highly reflective, highly dispersive (Lambertian) coating, and is important for side illumination.
The screen was shipped to Chile in Summer 2011, and was installed in October 2011.
Fiber Bundle for the DECal system
This custom made fiber bundle from Fibertech Optica will be fed into 4 modules spread evenly around the top ring of the telescope.
The light from the fibers will then be evenly projected onto the flat field screen.
J-P Rheault and Steven Villanuev working on DECal electronics
An example of some of the Prototype Results from the Carnegie Supernova Project second photometry release
For more information, please see our Publications