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Astron. Astrophys. 320, 167-171 (1997)

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2. Observations and data reduction

Optical imaging observations towards Class II YSOs in Bok globules (Yun & Clemens 1995) were carried out during the nights of 1993 December 13-16 using the European Southern Observatory 0.9 m Dutch telescope equipped with a 512 [FORMULA] 512 pixel CCD detector. Images were obtained using a set of filters which included broad-band B, V, R, I filters. The detector was used at a plate scale of 0.46 arcsec per pixel, resulting in a field of view of 3.9 [FORMULA] 3.9 arcmin2 on the sky. In addition, in 1994 December and 1995 December, we obtained medium resolution ([FORMULA] 7Å per pixel) optical spectra and additional R-band images, using the ESO Danish 1.54 m telescope equipped with the Danish Faint Object Spectrograph and Camera (DFOSC) detector. Calibration lamps (He and Ne) were observed immediately before or after each object spectrum.

Near-infrared observations were made in 1993 December 20 using the IRAC2 NICMOS 3 infrared array camera mounted on the ESO 2.2 m telescope. We obtained a set of 9 dithered frames in the JHK-bands, with a total integration time per frame of 30 seconds.

Standard CCD image reduction procedures (dark and bias subtraction, and flat-fielding) were applied to the optical CCD images, using the NOAO Image Reduction and Analysis Facility (IRAF 1). Similarly, standard IRAF packages were used to make the spectroscopic reductions (SPECRED).

Reduction of the near-infrared images were performed by subtraction of a sky frame (computed by median filtering of the 9 dithered images) followed by flat-fielding. The final flat-fielded images were subsequently corrected for the presence of bad pixels and mosaicked, co-adding the overlapping regions.

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998