High-resolution Fiber-fed Spectrograph Research Articles

An Exposure Meter of Lijiang Fiber-fed High-Resolution Spectrograph

In 2016, an exposure meter was installed on the Lijiang Fiber-fed High-Resolution Spectrograph to monitor the coupling of starlight to the science fiber during observations. Based on it, we investigated a method to estimate the exposure flux of the CCD in real time by using the counts of the photomultiplier tubes (PMT) of the exposure meter, and developed a piece of software to optimize the control of the exposure time. First, by using flat-field lamp observations, we determined that there is a linear and proportional relationship between the total counts of the PMT and the exposure flux of the CCD. Second, using historical observations of different spectral types, the corresponding relational conversion factors were determined and obtained separately. Third, the method was validated using actual observation data, which showed that all values of the coefficient of determination were greater than 0.92. Finally, software was developed to display the counts of the PMT and the estimated exposure flux of the CCD in real-time during the observation, providing a visual reference for optimizing the exposure time control.

High-Resolution Fiber-Fed Spectrograph for the 6-m Telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences: Assessment of Efficiency

Abstract—We report the results of laboratory tests of the first version of the high-resolution fiber-fed spectrograph designed for the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). During laboratory tests a spectral resolution of about 70 000 was achieved. The peak efficiency of the entire optical path of the spectrograph (without light losses at the CCD, primary mirror of the 6-m telescope, and in the atmosphere) at 620 nm and with the equivalent slit widths of the 1″.5 and 0″.75 are equal to 8% and 4%, respectively. The resolving power R = 70 000 and 100 000 can be reached with the sky aperture 0″.75 and 0″.4 respectively. In the current version of the spectrograph these regimes of operation are implemented by mechanic aperturing of the slit. A dedicated projecting camera has been developed and is currently manufactured to operate with a collimated 200-mm diameter beam, which will make it possible to increase the spectral resolution up to 100 000. A two-beam image slicer will be used to maintain the luminous efficiency of the instrument at least at the 6% level.

The Coude Echelle Spectrograph for the Lijiang 1.8m telescope

The Coude Echelle Spectrograph (CES) was originally mounted on Xinglong 2.16 m telescope in 1994. When the High Resolution Fiber-fed Spectrograph (HRS) was commissioned at Xinglong 2.16 m telescope, the red path of CES was moved to Lijiang 1.8 m telescope, following some redesign and reinstallation. The CES of Lijiang 1.8 m telescope has the spectral resolution (R = λ/Δλ) ranging from 20000 to 50000 corresponding to different slit widths. With a 2k × 2k PI CCD, CES has a wavelength coverage between 570 nm to 1030 nm. In particular, the resolution of 37000 at 0.5 mm slit corresponds to 1.3″ on the sky. The limiting magnitude is V = 11.5 with the use of the tip-tilt feedback system, and the S/N is about 40 for 1 hour exposure at 600 nm (R = 37000). During the installation of CES, the tip-tilt mirror technology had successfully fulfilled high precision guiding and tracking for high resolution spectral observation and significantly improved the observation efficiency.

Calibration Tests of a 25-GHz Mode-spacing Broadband Astro-comb on the Fiber-fed High Resolution Spectrograph (HRS) of the Chinese 2.16-m Telescope

A 25-GHz mode-spacing astro-comb with 470–720 nm wavelength coverage has been installed as the calibration source on the fiber-fed High Resolution Spectrograph (HRS) of the Chinese 2.16-m telescope at Xinglong Observatory. The calibration tests were carried out based on the single-channel system of HRS. The results have achieved a 2–8 times (for different orders) higher wavelength solution accuracy than the thorium argon (ThAr) lamp, and a short-term repeatability of 0.1 m s−1, which is around the photon noise limit. It proved that the coupling system linking the astro-comb to HRS successfully suppressed the negative effects of laser speckles. The comb-line overlapping exists in the acquired spectrum of the astro-comb on HRS. We demonstrated that when determining the comb-line center, the comb-line overlapping leads to a systematic bias, which is caused by asymmetrical sampling, and meanwhile a larger uncertainty. The correction for the systematic bias is feasible by simulating the overlapping comb lines according to actual comb-line spacing and pixel phase and then calculating the difference of the fitted line center with the true line center. A higher accuracy of wavelength solution has been achieved after correction.

The Xinglong 2.16-m Telescope: Current Instruments and Scientific Projects

The Xinglong 2.16-m reflector is the first 2-m class astronomical telescope in China. It was jointly designed and built by the Nanjing Astronomical Instruments Factory (NAIF), Beijing Astronomical Observatory (now National Astronomical Observatories, Chinese Academy of Sciences, NAOC), and Institute of Automation, Chinese Academy of Sciences in 1989. It is a Ritchey-Chrétien (R-C) reflector on an English equatorial mount and the effective aperture is 2.16 m. It had been the largest optical telescope in China for ∼18 years until the Guoshoujing Telescope (also called Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST) and the Lijiang 2.4-m telescope were built. At present, there are three main instruments on the Cassegrain focus available: the Beijing Faint Object Spectrograph and Camera (BFOSC) for direct imaging and low-resolution (R ∼ 500–2000) spectroscopy, the spectrograph made by Optomechanics Research Inc. (OMR) for low-resolution spectroscopy (the spectral resolutions are similar to those of BFOSC) and the fiber-fed High Resolution Spectrograph (HRS; R ∼ 30,000–65,000). The telescope is widely open to astronomers all over China as well as international astronomical observers. Each year there are more than 40 ongoing observing projects, including 6–8 key projects. Recently, some new techniques and instruments (e.g., astro-frequency comb calibration system, polarimeter, and adaptive optics) have been or will be tested on the telescope to extend its observing abilities.

Upgrade of the fiber-fed spectrograph of the Kourovka Astronomical Observatory

We report the results of testing the high-resolution fiber-fed spectrograph of Kourovka Astronomical Observatory of the Ural Federal University in 2010–2012 and the corresponding operation experience, and demonstrate the need for an upgrade of the instrument. We also describe the modifications that were made to the design of the spectrograph during the start of its regular operation in 2010 and the refurbishment of its suspended part carried out in 2013, which allowed to expand the capabilities of the instrument.

CHIRON TOOLS: Integrated Target Submission, Scheduling and Observing Systems for a High-Resolution Fiber-Fed Spectrograph

The CHIRON spectrometer is a new high-resolution, fiber-fed instrument on the 1.5 m telescope at Cerro Tololo Inter-America Observatory (CTIO). To optimize use of the instrument and limited human resources, we have designed an integrated set of Web applications allowing target submission, observing script planning, nightly script execution and logging, and access to reduced data by multiple users. The unified and easy-to-use interface has dramatically reduced the time needed to submit and schedule observations and improved the efficiency and accuracy of nightly operations. We present our experience to help astronomers and project managers who need to plan for the scope of effort required to commission a queue-scheduled facility instrument.