The Most Efficient Tool for very High Resolution and very High Signal to Noise Ratio Spectral Observation of Stars

1988 ◽  
pp. 15-21
Author(s):  
S. Y. Jiang
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Spectral Observation ◽  
High Signal ◽  
Signal To Noise ◽  
Efficient Tool ◽  
Noise Ratio ◽  
Very High

scholarly journals The Most Efficient Tool for very High Resolution and very High Signal to Noise Ratio Spectral Observation of Stars

1988 ◽  
Vol 132 ◽  
pp. 15-21
Author(s):  
S. Y. Jiang
Keyword(s):  
High Efficiency ◽  
Signal To Noise Ratio ◽  
Spectral Observation ◽  
Resolving Power ◽  
High Signal ◽  
Large Telescope ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Very High ◽  
Light Efficiency

Today even for the most efficient spectrograph combined with a large telescope the light efficiency is only about 0.01 to 0.1 for spectral resolving power R larger than 10000 in optical wavelength band (OWB). Consequently for a very high signal to noise ratio spectral observation of rather bright stars still needs very large telescope. The main reason is that there are too many optical surface with rather low light efficiency and serious light loss at the limited slit width. In this paper we suggest a very high efficiency telescope-spectrograph system which will give an overall light efficiency varied from 0.21 at 400 nm to 0.44 at 700 nm, four fold higher than before. Using this system for R = 100000, S/N larger than 100 the limiting magnitude will be about 15.

Anti-Vibration Sub Allows A Very High Signal-To-Noise Ratio And Improves Borehole Quality

2013 ◽  
Author(s):  
Paul Christian Bates ◽  
Chakib Bouziane ◽  
Denise Nicholl ◽  
Reina Teelken ◽  
Mohammed Zuki Bin Bidi ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
High Signal ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Very High

Proposal for a Laue lens with quasi-mosaic crystalline tiles

2011 ◽  
Vol 44 (6) ◽  
pp. 1255-1258 ◽  
Author(s):  
Vincenzo Guidi ◽  
Valerio Bellucci ◽  
Riccardo Camattari ◽  
Ilaria Neri
Keyword(s):  
High Resolution ◽  
Crystal Size ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Laue Lens ◽  
Crystalline Anisotropy ◽  
Order Of Magnitude ◽  
Mosaic Crystals ◽  
Noise Ratio ◽  
Very High

Quasi-mosaicity is an effect of secondary bending within a crystal driven by crystalline anisotropy. This effect can be used to fabricate a series of curved crystals for the realization of a Laue lens. It is highlighted that crystals bent by the quasi-mosaic effect allow very high resolution focusing with respect to mosaic crystals. Under the same conditions for energy passband, crystal size and flux of incident photons, a Laue lens based on quasi-mosaic crystals would increase the signal-to-noise ratio by about an order of magnitude compared to the same lens with mosaic crystals. Moreover, no mosaic defocusing occurs for quasi-mosaic crystals.

scholarly journals Seismology of southern Be stars

1994 ◽  
Vol 162 ◽  
pp. 104-105
Author(s):  
Eduardo Janot-Pacheco ◽  
Nelson Vani Leister
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Ccd Camera ◽  
High Signal ◽  
Be Stars ◽  
Signal To Noise ◽  
Photometric Variability ◽  
Spectroscopic Observations ◽  
Photometric Observations ◽  
Noise Ratio

We have started in 1990 a search for moving bumps in the HeI λ 667.8 nm of mainly southern, bright Be stars. The objects of our sample have been selected on the basis of photometric variability (Cuypers et al., 1989). High resolution (R≥ 30,000), high signal-to-noise ratio (S/R≥ 300) spectroscopic observations have been performed at the brazilian Laboratório Nacional de Astrofísica with a CCD camera attached to the coudé spectrograph of the 1.60 m telescope (e.g. Table I). Several hundred spectra have been taken during the last three years. Photometric observations simultaneous with spectroscopy were made on the same site in July 1992 with a two-channel photometer (Stromgren b filter) and a CCD camera (Johnson B filter) installed at two 0.60 m telescopes. The idea is try to disentangle the controversy between NRP and RM models with the help of simultaneous spectroscopy and photometry.

Excited states of HI and DI and their negative ions between 10 and 20 eV

1988 ◽  
Vol 66 (7) ◽  
pp. 564-569
Author(s):  
P. Marmet ◽  
Hamid Nasrallah
Keyword(s):  
Excited States ◽  
Signal To Noise Ratio ◽  
Rydberg States ◽  
Negative Ions ◽  
Ionization Efficiency ◽  
High Signal ◽  
Signal To Noise ◽  
Noise Ratio ◽  
The Impact ◽  
Very High

The ionization-efficiency curves of HI and DI, obtained by the impact of monoenergetic electrons between 10 and 20 eV, are presented with a very high signal-to-noise ratio. Several new Rydberg states between the 2Π(3/2) and 2Π(1/2) limits and also below the 2Σ+ limit have been identified. Also, the first two 6s and 6p Rydberg levels with configuration (5sσ)1(5pσ)2(5pπ)4nlλ have been observed at 17.3 and 18.6 eV, respectively. The results obtained in DI confirm the structures observed in HI.

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