An overview of the Seimei telescope, a 3.8 m optical infrared telescope located on Mt. Chikurinji in the Okayama prefecture of Japan, is presented. Seimei is a segmented-mirror telescope whose primary mirror consists of 18 petal-shaped segments. The telescope tube supporting the thin segmented mirrors is structurally incorporated within large arc-rails providing the elevation axis. The tube has a light-weight homologous structure designed with a genetic algorithm. The total weight of the telescope tube, including 1.4-ton optics, is only 8 tons. By virtue of its light weight, the telescope is able to point at an object anywhere in the observable sky within one minute. The telescope is operated by Kyoto University in collaboration with the National Astronomical Observatory of Japan (NAOJ). Half of the telescope time is used by Kyoto University. The remaining time is open to the Japanese astronomical community. NAOJ is responsible for the management of the open-use time, including handling of the observation proposals. The telescope is now regularly performing scientific observations on the basis of a variety of proposals.
Observations of transient objects, such as short gamma-ray bursts (GRBs) and electromagnetic counterparts of gravitational wave sources, require prompt spectroscopy. To carry out prompt spectroscopy, we developed an optical-fiber integral field unit (IFU) and connected it with an existing optical spectrograph KOOLS. KOOLS with IFU, hereafter KOOLS-IFU, was mounted on the Okayama Astrophysical Observatory 188-cm telescope. The fiber core and cladding diameters of the fiber bundle are 100 µm and 125 µm, respectively, and 127 fibers are hexagonally close-packed in the sleeve of the two-dimensional (2D) fiber array. We conducted test observations to measure the KOOLS-IFU performance and obtained the following conclusions: (1) the spatial sampling is 2. ′′ 34 ± 0. ′′ 05 per fiber, and the total field of view (FoV) is 30. ′′ 4 ± 0. ′′ 65 with 127 fibers; (2) the observable wavelength and the spectral resolving power of the grisms of KOOLS are 4030-7310Å and 400-600; 5020-8830Å and 600-900; 4160-6000Å and 1000-1200; and 6150-7930Å and 1800-2400, respectively; and (3) the estimated limiting magnitude is 18.2-18.7 AB mag during 30-min exposure under the optimal condition.
We report on the development of a wide-field near-infrared (0.9–2.5$\, \mu$m) camera built as a renewal of the existing classical Cassegrain 0.91 m telescope at Okayama Astrophysical Observatory. The optics system was replaced with fast hybrid optics (f/2.5) composed of forward Cassegrain optics and quasi-Schmidt optics, which results in an effective image circle of 52 mm diameter on the focal plane. The new camera, called the Okayama Astrophysical Observatory Wide-Field Camera (OAOWFC), has imaging capabilities in the $Y$, $J$, $H$, and $K_{\rm s}$ bands over a field of view of $0.^{\!\!\!\circ }47 \times 0.^{\!\!\!\circ }47$ with a HAWAII-1 HgCdTe PACE focal plane array. The primary purpose of OAOWFC is to search for variability in the Galactic plane in the $K_{\rm s}$ band and to promptly follow up transients. We have demonstrated a photometric repeatability of 2% in the densest field in the northern Galactic plane and successfully discovered previously unreported variable stars. The observations of OAOWFC are fully autonomous, and we started scientific operations in 2015 April.
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