We report intermediate resolution H alpha spectroscopy of the black hole candidate Nova Muscae 1991 during quiescence. We classify the companion star as a K3-K4V which contributes 85 plusmn 6 percent to the total flux from the binary. The photospheric absorption lines are broadened by 106 plusmn 13 km s^-1 with respect to template field stars

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This paper discusses the Galactic plane as a case history of the application of different kinds of data bases to the problem of the large-scale Galactic structure. The shape of the Galaxy, and tilts and warps in the Galactic plane are examined.

Segments alignment is one of the fundamental factors affecting the shape of the PSF of a segmented mirror telescope. Tilt and piston of each segment must be very well and uniformly adjusted in relation with the rest of the segments. The Hartmann-Shack sensor is very efficient in detecting the local wavefront tilt, but the task to take measurements

This paper examines the oxygen abundance of 24 main-sequence turn-off and subgiant stars through the permitted O I triplet near $lambda$7774 {AA}. In agreement with prior investigators, we find that the O abundance from the triplet is about 0.53 dex higher than is typically found from other means such as the [O I] $lambda$6300 {AA} line or the UV

The future large telescope for the Observatorio del Roque de los Muchachos will have a 10 m diameter segmented primary made of hexagonal elements (similar to the Keck I primary). The telescope optical configuration is being selected to achieve excellent image quality and low emissivity out to the mid-IR. The design includes provision for two