• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.36.1-36.1
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• 2010

OFC (Optical Frequency Comb) is an optical spectrum which consists of equidistant lines in frequency space. OFC can thus be used as an optical ruler. Since it was demonstrated in late 1990s, it is revolutionizing many fields in frequency metrology such as the measurement of absolute optical frequencies, the measure ratios of optical frequencies with extremely high precision. It is also used in high-precision spectroscopy. In astronomy, OFC can be used as a very accurate and stable wavelength standard for a high resolution spectrograph to measure the radial velocity of celestial bodies with extremely high accuracy of about several tens cm/s. In our presentation, we will introduce some basic concepts of OFC and some issues to use it in astronomical spectrograph. We will also present our plan to develop a high resolution spectrograph with OFC.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.40.4-40.4
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• 2020

Kyung Hee university invented the Transformable Reflective Telescope (TRT) for optical experiment and education. The TRT kit can transform into three optical configurations from Newtonian to Cassegrain to Gregorian by exchanging the secondary mirror. We designed the Ebert-Fastie spectrograph as an extension of the TRT kit. The primary mirror of the TRT kit serves as both collimator and camera lens, and the reflective grating as the dispersing element is placed along the optical axis of the primary mirror. We designed and fabricated the grating holder and the source units using 3D printer. Baffle was also fabricated to suppress the stray light, which was reduced by 83%. The spectrograph can observe the optical wavelength range (4000Å~7000Å). Measured resolving power (R=λ/Δλ) was ~700 with slit width of 0.18mm. The spectrograph is optimized for f/24, and the spectral pixel scale is 0.49Å/pixel with Canon 550D detector. We present the sample spectra of discharged Ne, Ar and Kr gases. The flexible setting and high performance make this spectrograph a useful tool for education and experiment.

• Publications of The Korean Astronomical Society
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• v.15 no.spc1
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• pp.119-126
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• 2000

The BOES (BOAO Echelle Spectrograph), a fiber-fed echelle spectrograph of the BOAO 1.8 m telescope, has been designed and now is being manufactured. The BOES follows a white pupil design collimated with two off-axis parabolic mirrors. The 136mm collimating beam leaving the 41.59 grooves/mm R4 echelle grating is refocused near the narrow folding mirror. Through the two cross-disperser prisms and $\phi250 mm(f/1.5)$ transmission camera, the beam images on EEV $2k\times4k$ CCD. The BOES can take the wavelength range of 3700 to $10100{\AA}$ at a single spot with spectral resolution R = 20000 to 40000 depending on the fiber set employed. We describe the key sciences and performance, current status of construction, and future plan of the BOES.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.675-677
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• 2015

A data simulator and reduction package for the Devasthal Optical Telescope Integral Field Spectrograph (DOTIFS) has been developed. Since data reduction for the Integral Field Spectrograph (IFS) requires complicated procedures due to the complex nature of the integral spectrograph, common reduction procedures are usually not directly applicable for such an instrument. Therefore, the development of an optimized package for the DOTIFS is required. The data simulator observes artificial object and simulates CCD images for the instrument considering various effects; e.g. atmosphere, sky background, transmission, spectrograph optics aberration, and detector noise. The data reduction package has been developed based on the outcomes from the DOTIFS data simulator. The reduction package includes the entire processes for the reduction; pre-processing, flat-fielding, and sky subtraction. It generates 3D data cubes as a final product, which users can use for science directly.

• Journal of The Korean Astronomical Society
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• v.34 no.1
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• pp.41-45
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• 2001

We tested the characteristics of the BOAO Medium Dispersion Spectrograph (MDS) such as the CCD capabilities, wavelength shift by gravity direction variation, slit illumination function and efficiency. Then we calculated the appropriate exposure time to obtain the given S/N ratio for several given magnitudes. Also the remaining problems to be improved were discussed.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.100.2-100.2
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• 2014

The DOTIFS is a new multi-object Integral Field Spectrograph (IFS) planned to be designed and built by the Inter-University Center for Astronomy and Astrophysics, Pune, India, (IUCAA) for cassegrain side port of the 3.6m Devasthal Optical Telescope (DOT) being constructed by the Aryabhatta Research Institute of Observational Sciences, Nainital. (ARIES) It is a multi-integral field unit (IFU) spectrograph which has 370-740nm wavelength coverage with spectral resolution R~1200-2400. Sixteen IFUs with microlens arrays and fibers can be deployed on 8 arcmin field. Each IFU has $8.7^{{\prime}{\prime}}{\times}7.4^{{\prime}{\prime}}$ field of view with 144 spaxel elements. 2304 fibers coming from IFUs are dispersed by eight identical spectrographs with all refractive and all spherical optics. In this work, we show optical design of the DOTIFS spectrograph. Expected performance and result of tolerance and thermal analysis are also shown. The optics is comprised of f=520mm collimator, broadband filter, dispersion element and f=195mm camera. Pupil size is determined as 130mm from spectral resolution and budget requirements. To maintain good transmission down to 370nm, calcium fluoride elements and high transmission optical glasses have been used. Volume Phase Holographic grating is selected as a dispersion element to maximize the grating efficiency and to minimize the size of the optics. Detailed optics design report had been documented. The design was finalized through optical design review and now ready for order optics.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.117-120
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• 2005

Current instrumentation activities and the open user status of Okayama Astrophysical Observatory (OAO) are reviewed. There are two telescopes in operation and one telescope under reforming at OAO. The 188cm telescope is provided for open use for more than 200 nights in a year. The typical over-subscription rate of observation proposals for the 188cm telescope is ${\~}$ 1.5 - 2. The 50cm telescope is dedicated to $\gamma$-ray burst optical follow-up observation and is operated in collaboration with Tokyo Institute of Technology. The 91cm telescope will become a new very wide field near-infrared camera in two years. The high-dispersion echelle spectrograph (HIDES) is the current primary instrument for the open use of the 188cm telescope. Two new instruments, an infrared multi-purpose camera (ISLE) and an optical low-dispersion spectrograph (KOOLS), are now under development. They will be open as common use instruments in 2006.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.96-102
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• 2011

Simultaneous measurements using a scanning spectrograph system and transmissometer were performed for the first time over an urban site in Gwangju, Korea, to derive the ambient $NO_2$ volume mixing ratio. The differential slant column densities retrieved from the scanning spectrograph system were converted to volume mixing ratios using the light traveling distance along the scanning line of sight derived from the transmissometer light extinction coefficients. To assess the performance of this system, we compared the derived $NO_2$ volume mixing ratios with those measured by an in situ chemiluminescence monitor under various atmospheric conditions. For a cloudless atmosphere, the linear correlation coefficient (R) between the two data sets (i.e., data derived from the scanning spectrograph and from the in situ monitor) was 0.81; the value for a cloudy atmosphere was 0.69. The two sets of $NO_2$ volume mixing ratios were also compared for various wind speeds. We also consider the measurement errors, as estimated from an error propagation analysis.

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.16-17
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• 2004

• The Bulletin of The Korean Astronomical Society
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• v.22
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• pp.19.2-20
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• 1997