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ARC 3.5m | ARCES (Echelle)
Last updated: Feb 23, 2016 - AB
Table of Contents
The ARC Echelle Spectrograph (ARCES) is a high resolution, cross-dispersed visible light spectrograph. It captures the entire spectrum between 3200-10000Å (between the atmospheric cutoff and the CCD cutoff) in a single exposure on a 2048x2048 SITe CCD. The spectrograph provides a resolution (2.5 pixels) of R~31,500.
ARCES is permanently mounted on the NA1 port of the 3.5m telescope. This means that it does not require an instrument change to use ARCES with another instrument during one night. ARCES is a single point spectrograph, so the small (!) field of view rotates as an object is tracked across the sky.
The spectra are recorded in ~120 orders that are distributed across the chip. Longer wavelength orders are located at the bottom (low row numbers) of the chip, and shorter wavelength order are located at higher row numbers. Each order is curved significantly, and within each order, wavelength decreases with increasing row number. Compared with some other echelle spectrographs, the orders are relatively narrow and closely spaced, which may require users to take special care when flat fielding and extracting spectra.
The following table gives locations of 107 orders, along with the approximate central wavelength and dispersion of the order. The dispersions are negative, indicating that wavelength decreases as column number increases. Note, as of 07-01-2013, there is a new grating in the spectrograph. This table is still useful, but be aware that some of the lines may fall between orders.
Order ID Row (at chip center) Wavelength (chip center) Dispersion Range (Å / 1600 pixels) Order ID Row (at chip center) Wavelength (chip center) Dispersion Range (Å / 1600 pixels) Order ID Row (at chip center) Wavelength (chip center) Dispersion Range (Å / 1600 pixels)