Detailed low spectral resolution observations of the spectrum have been made for three early spectral type standard stars, HR718, HR1544, HR3454, respectively, for the wavelength region 4,300 A to 7,500 A, using the Bohyunsan Optical Astronomy Observatory (BOAO) Middle- Dispersion Spectrograph. These standard stars were chosen from well-known bright northern standard stars. All of the observed long slit spectral data has been reduced and analyzed using the IRAF reduction procedure. The derived extinction coefficients are compared with the other observatory result. The derived value can be used in the determination of flux calibration of BOAO spectroscopic observation. However, until the high quality data are secured from a new series of observation in the blue region and are re-analyzed together, the extinction coefficients below the 4,000 A wavelength remains unknown.

• 김강민(천문대 보현산 천문대) | Kim Kang-Min (Bohyunsan Optical Astronomy Observatory, Korea Astronomy Observatory)
• 손동훈(경희대학교 우주과학과) | Son Dong-Hoon (Department of Astronomy and Space Science, Kyung Hee University)
• 형식(천문대 보현산 천문대) | Hyung Siek (Bohyunsan Optical Astronomy Observatory, Korea Astronomy Observatory)
• 윤태석(경북대학교 천문대기과학과) | Yoon Tae-Seog (Department of Astronomy and Atmospheric Science, Kyungpook National University)