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Imaging atmospheric Cˇerenkov telescopes are complex instruments that use Earth's atmosphere as an integral part of the detector system. For the eight years of observations with the High Energy Stereoscopic System (H.E.S.S.) in Namibia, we study the long-term behaviour of the quality criteria used to select data taken under good atmospheric conditions and in the absence of hardware problems. The overall yield in Cˇerenkov photons varies strongly with time for H.E.S.S., due to degradation of mirrors and natural and man-made variations of atmospheric transparency, on time scales from hours to seasons. We present robust cuts that cope with these effects over the full dataset of H.E.S.S. and examine the influence of the cuts on energy reconstruction and spectral parameters. [ABSTRACT FROM AUTHOR]

H.E.S.S. TeV gamma-ray telescope discovered many new sources on the Galactic plane. They should be Galactic particle accelerators but their nature is still unknown since they have few information in other wavelength. Jp-US X-ray telescope Suzaku has made follow-up observations for several TeV unID sources, using the low and stable background and the large effective area. The results are full of varieties; compact counterparts (HESS J1804-216, HESS J1837-609) and diffuse counterparts (HESS J1614-518, CTB 37B). Most interesting results are no-detection even with long exposure (HESS J1616-508, HESS J1745-303). In this talk, we present one of the most interesting result, HESS J1745-303, which is located on near the Galactic center. [ABSTRACT FROM AUTHOR]