A concept is described for the high-accuracy absolute calibration of the instrumental polarization introduced by the primary mirror of a large-aperture telescope. This procedure requires a small aperture with polarization-calibration optics (e.g., mounted on the dome) followed by a lens that opens the beam to illuminate the entire surface of the

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We report R band imaging polarimetry of SN 2004bv in NGC 6907 on June 19.299 (UT middle of observation), i.e., two weeks after maximum. We have obtained [ 0.11 ± 0.02] % at position angle 118.7 ° for the observed polarization. The average foreground polarization from field objects was estimated to be [ 0.12 ± 0.02] % at PA 163.4 °, consistent with

We report on the linear polarimetric observations in the Johnson I-band filter of 44 ultracool dwarfs with spectral types between M6 and L7.5, corresponding to effective temperatures in the range 2800-1400 K, and one M4.5-type star. Based on our measurements of polarization (P) and their associated error bars (σP), 11 (10 L and 1 M) dwarfs appear

Las estrellas en rotación tienen gran importancia en Astrosismología. En la actualidad, existe una gran cantidad de observaciones de estrellas de tipo delta Scuti en las cuales se han detectado frecuencias de oscilación, aunque su estructura no está aún bien entendida. Desafortunadamente, hasta la fecha, los métodos disponibles para calcular las

Planetary nebulae (PNe) are known to possess a variety of small-scale structures that are usually in a lower ionization state than the main body of the nebulae. The morphological and kinematic properties of these low-ionization structures (LISs) vary from type to type in the sense that LISs can appear in the form of pairs of knots, filaments, jets