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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 826-830 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We describe here the details of the concept, the construction, and the performance of an accurate and inexpensive sidereal tracking drive unit (SDU) for the 1-m or larger class of astronomical telescopes. The SDU is tunable and has a very highly stable and undistorted sinusoidal wave shape. The SDU consists mainly of a variable drift-free drive rate generator and a distortion-free, low-cost power amplifier. Tracking accuracies of less than a couple of arcseconds in sky are achieved in 60 min of observation time. The unit can also be used in negative feed back mode to correct any errors in the tracking system. The accuracies in frequency stability obtainable with the SDU and the feasibility of operation in negative feedback mode for correcting tracking errors are not possible in the commercially available battery back-up uninterrupted power supply (UPS) units. The total cost of the SDU currently works out to be approximately $200 (US) and requires about one man-month for building and testing.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 114 (1985), S. 351-356 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have obtained Hα emission line profiles from R Aquarii, a Mira variable surrounded by a complex nebulosity, using a very high-resolution Fabry-Pérot spectrometer. A new feature that was seen in our observations is the fact that the line profile shows a splitting which we interpret as due to two expanding shells surrounding the star with velocities of ∼5 km s−1 and ∼15 km s−1. The expansion velocities show an acceleration outwards due perhaps to the radiation pressure caused momentum transfer. Possible periodic variation of radial velocity derived from observations is discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 117 (1985), S. 209-216 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We describe here a far-infrared photometer capable of detecting simultaneously in three bands in the region 20–120 microns, each band having an array of 3 or 4 photoconductive detectors. We present and discuss its laboratory performance and the results obtained on the planet Venus during an air-borne observational programme using a 32.5 cm telescope. We also present the atmospheric spectra obtained by a Michelson interferometer aboard the aircraft.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We describe here a scanning piezo-electric Fabry-Pérot spectrometer operating in the photoncounting mode whose plate spacing and parallelism are maintained by a servo-controlled system, ensuring high accuracy, for the study of emission lines from extended astronomical objects in the spectral range 4500–7000 Å. Details of the optical set-up and the Data Acquisition System (DAS) are described. Its performance at the Cassegrain focus of the 1 m telescope at Kavalur is discussed. Some line profiles on planetary nebulae studied with the above spectrometer are also presented.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 205 (1993), S. 283-295 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Ring nebulae are known to form around stars like the Wolf-Rayet and the Of stars. The dust in these nebulae is heated by the central star and, therefore, provides a positive clue to the origin of the nebulae, complementing the optical techniques. A systematic search has been carried out to study the infra-red emission from these nebulae based on the IRAS data. The influence of the local interstellar material properties on the formation of nebular dust is studied.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 220 (1994), S. 83-95 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study here the dynamics of an extended shell of relatively low-mass (almost zero-mass) particles around massive binary systems by computer simulations in the framework of approximately restricted three-body problem with a set of several initial conditions concerning the massesM 1 andM 2 of the binary components surrounded byN test particles in uniform random distribution on a spherical envelope of radiusR expanding with a velocityV. We apply this model to binary galaxy systems with a halo of baryonic dark matter, e.g., massive black holes, globular clusters, and giant molecular clouds. It is shown that, initially, the shell expands homologously with decreasing velocity and then, falls back into the system forming zones of compressed matter. At some moment there could be a collapse or these particles onto the heavier component of the binary. Further in time, a number of particles escape from the system. We consider a number of different models with different initial parameters. For models with smallerR andV, about one-half of the particles escape from the system; while for larger values the shell disrupts as a whole. The escaping particles form a collimated flow in the plane of the orbit of the binary. The position of the flow and the directions of motions depend on the position of the heavier component of the binary at the moment of the closest approach of the particles and on the ratioM 1/M 2.
    Materialart: Digitale Medien
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