We present echelle spectroscopy in the 3550 to 7010 A range for two positions of the Orion Nebula. The data were obtained with the 2.1-m telescope at Observatorio Astronomico Nacional in San Pedro Martir, Baja California. We have measured the intensities of several permitted lines of C(+) , N(+) , N(++) , O(0) , O(+) , Ne(0) , Si(+) , Si(++) which

Effects of differential extinction across the Earth's atmosphere on astronomical photometry are reviewed. Under the same circumstances when a rotating extended object is observed spectrometrically, a residual radial velocity is obtained which varies during the day. In the case of integral sunlight observations, this effect was calculated along the

Aims:The role of longitudinal structuring of the surrounding corona on the modes of oscillation of a coronal magnetic flux tube was studied in Donnelly et al. (2006) for a piecewise uniform profile. Here we investigate whether a more realistic continuous exponential profile changes the conclusions drawn from that paper. Methods: A partial

ELMER is a multi-purpose Camera&Spectrograph in the optical range for the GTC. ELMERs electro-mechanical design was based in well known, straightforward and reliable solutions, hence each mechanism is based in a wheel driven by a pre-loaded worm gear transmission, except focusing of the focal plane on the CCD which is based in a translation stage

ELMER is a visible imager-spectrograph currently scheduled to be in operation at the GTC on Day One. The design phase of the ELMER Structure and Mechanisms ended on November 2002. Since then, after manufacturing and mechanical integration, an exhaustive test campaign at factory was carried out. We present the fabrication and assembly highlights and