Night Sky Spectrum Research Articles

IFU Unit in Scorpio-2 Focal Reducer for Integral-Field Spectroscopy on the 6-m Telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences

We describe the scheme and design features of the new IFU unit (Integral Field Unit) meant to perform integral-field spectroscopy as a part of SCORPIO-2 focal reducer, which is mounted in the prime focus of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The design of the unit is based on the principle of the formation of array spectra using a lens raster combined with optical fibers. The unit uses a rectangular raster consisting of 22x22 square 2-mm diameter lenses. The image of the object is transferred by an optical system with a 23x magnification from the focal plane of the telescope to the plane of the lens raster. The image scale is 0.75"/lens and the field of view of the instrument has the size of 16.5"x16.5". The raster also contains two extra 2x7 lens arrays to acquire the night-sky spectra whose images are offset by $\pm$3' from the center. Optical fibers are used to transform micropupil images into two pseudoslits located at the IFU collimator entrance. When operating in the IFU mode a set of volume phase holographic gratings (VPHG) provides a spectral range of 4600-7300 \AA\ and a resolution $\lambda/\delta\lambda$ of 1040 to 2800. The quantum efficiency of SCORPIO-2 field spectroscopy is 6-13% depending on the grating employed. We describe the technique of data acquisition and reduction using IFU unit and report the results of test observations of the Seyfert galaxy Mrk 78 performed on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences.

LICA AstroCalc, a software to analyze the impact of artificial light: Extracting parameters from the spectra of street and indoor lamps

The night sky spectra of light-polluted areas is the result of the artificial light scattered back from the atmosphere and the reemission of the light after reflections in painted surfaces. This emission comes mainly from street and decorative lamps. We have built an extensive database of lamps spectra covering from UV to near IR and the software needed to analyze them. We describe the LICA-AstroCalc free software that is a user friendly GUI tool to extract information from our database spectra or any other user provided spectrum. The software also includes the complete color database of paints from NCS comprising 1950 types. This helps to evaluate how different colors modify the reflected spectra from different lamps. All spectroscopic measurements have been validated with recommendations from CIELAB and ISO from NCS database.

The Night Sky Spectrum of Xinglong Observatory: Changes from 2004 to 2015

We present spectroscopic measurements on the night sky of Xinglong Observatory for a period of 12 years from 2004 to 2015. The spectra were obtained on moonless clear nights using the OMR spectrograph mounted on a 2.16-m reflector with a wavelength coverage of 4000–7000 Å. The night sky spectrum shows the presence of emission lines from Hg i and Na i due to local artificial sources, along with the atmospheric emission lines, i.e., O i and OH molecules, indicating the existence of light pollution. We have monitored the night sky brightness during the whole night and found some decrement in the sky brightness with time, but the change is not significant. Also, we monitored the light pollution level in different azimuthal directions and found that the influence of light pollution from the direction of Beijing is stronger compared with that from the direction of Tangshan and other areas. An analysis of night sky spectra for the entire data set suggested that the zenith sky brightness of Xinglong Observatory has brightened by about 0.5 mag arcsec−2 in the V and B bands from 2004 to 2015. We recommend consecutive spectroscopic measurements of the night sky brightness at Xinglong Observatory in the future, not only for monitoring but also for scientific reference.

New device for monitoring the colors of the night

The introduction of LED lighting in the outdoor environment may increase the amount of blue light in the night sky color spectrum. This can cause more light pollution due to Rayleigh scattering of the shorter wavelengths. Blue light may also have an impact on circadian rhythm of humans due to the suppression of melatonin. At present no long-term data sets of the color spectrum of the night sky are available. In order to facilitate the monitoring of levels and variations in the night sky spectrum, a low cost multi-filter instrument has been developed. Design considerations are described as well as the choice of suitable filters, which are critical – especially in the green wavelength band from 500 to 600nm. Filters from the optical industry were chosen for this band because available astronomical filters exclude some or all of the low and high-pressure sodium lines from lamps, which are important in light pollution research. Correction factors are calculated to correct for the detector response and filter transmissions. Results at a suburban monitoring station showed that the light levels between 500 and 600nm are dominant during clear and cloudy skies. The relative contribution of blue light increases with a clear moonless night sky. The change in color spectrum of the night sky under moonlit skies is more complex and is still under study.

Ultrafast laser inscription: an enabling technology for astrophotonics

The application of photonics to astronomy offers major advantages in the area of highly-multiplexed spectroscopy, especially when applied to extremely large telescopes. These include the suppression of the near-infrared night-sky spectrum [J. Bland-Hawthorn et al, Opt. Express 12, 5902 (2004), S. G. Leon-Saval et al, Opt. Lett. 30, 2545 (2005)] and the miniaturisation of spectrographs so that they may integrated into the lightpath of individual spatial samples [J. Bland-Hawthorn et al, Proc SPIE 6269, 62690N (2006)]. Efficient collection of light from the telescope requires multimode optical fibres and three-dimensional photonic devices. We propose ultrafast laser inscription (ULI) [R. R. Thomson et al, Opt. Express 15, 11691 (2007)] as the best technology to fabricate 3D photonic devices for astrophotonic applications.

The case for OH suppression at near-infrared wavelengths

We calculate the advances in near-infrared (NIR) astronomy made possible through the use of fibre Bragg gratings to selectively remove hydroxyl emission lines from the night sky spectrum. Fibre Bragg gratings should remove OH lines at high resolution (R= 10 000), with high suppression (30 dB) whilst maintaining high throughput (≈90 per cent) between the lines. Devices presently under construction should remove 150 lines in each of the J and H bands, effectively making the night sky surface brightness ≈4 mag fainter. This background reduction is greater than the improvement adapative optics makes over natural seeing; photonic OH suppression is at least as important as adaptive optics for the future of cosmology. We present a model of the NIR sky spectrum, and show that the interline continuum is very faint (≈80 photons s−1m−2arcsec−2μm−1 on the ecliptic plane). We show that OH suppression by high dispersion, that is, ‘resolving out’ the skylines, cannot obtain the required level of sensitivity to reach the interline continuum due to scattering of light. The OH lines must be suppressed prior to dispersion. We have simulated observations employing fibre Bragg gratings of first light objects, high-redshift galaxies and cool, low-mass stars. The simulations are of complete end-to-end systems from object to detector. The results demonstrate that fibre Bragg grating OH suppression will significantly advance our knowledge in many areas of astrophysics, and in particular will enable rest-frame ultraviolet observations of the Universe at the time of first light and reionization.

THE NIGHT SKY SPECTRUM OF MOUNT BOHYUN

Spectrophotometry of the night sky over Mount Bohyun is presented for the nearly entire visible wavelengths of <TEX>$3600{\~}$8600{\AA}$</TEX>. The data was obtained under moonless clear sky in February 2004 with the 1.8-m telescope and the long slit spectrograph. The sky spectrum shows a number of strong emission lines originated from light pollution, especially due to high pressure sodium lamps. When compared to the night sky of Kitt Peak, our sky continuum is 1 to 2 magnitude brighter at all wavelengths, the worst being around the broad emission region near 6000<TEX>${\AA}$</TEX>. The night sky spectrum presented here with almost complete line identifications is a useful reference for arc-independent wavelength calibrations to check the gravity flexure of the spectrograph and the wavelength shift between FeNeArHe arc frames and science frames.

The First Detections of the Extragalactic Background Light at 3000, 5500, and 8000 Å. II. Measurement of Foreground Zodiacal Light

We present a measurement of the absolute surface brightness of the zodiacal light (3900-5100 A) toward a fixed extragalactic target at high ecliptic latitude based on moderate-resolution (~1.3 A pixel-1) spectrophotometry obtained with the du Pont 2.5 m Telescope at the Las Campanas Observatory in Chile. This measurement and contemporaneous Hubble Space Telescope data from the Wide Field Planetary Camera 2 and Faint Object Spectrograph comprise a coordinated program to measure the mean flux of the diffuse extragalactic background light (EBL). The zodiacal light at optical wavelengths results from scattering by interplanetary dust so that the zodiacal light flux toward any extragalactic target varies seasonally with the position of the Earth. This measurement of zodiacal light is therefore relevant to the specific observations (date and target field) under discussion. To obtain this result, we have developed a technique that uses the strength of the zodiacal Fraunhofer lines to identify the absolute flux of the zodiacal light in the multiple-component night-sky spectrum. Statistical uncertainties in the result are 0.6% (1 σ). However, the dominant source of uncertainty is systematic errors, which we estimate to be 1.1% (1 σ). We discuss the contributions included in this estimate explicitly. The systematic errors in this result contribute 25% in quadrature to the final error in our coordinated EBL measurement, which is presented in the first paper of this series.

Identification of the night sky spectrum at Xinglong Station, Beijing Astronomical Observatory: JIANG Xiao-jun, XU Da-wei & HU Jing-yao Beijing Astronomical Observatory, CAS, Beijing 100080

Identification of the night sky spectrum at Xinglong Station, Beijing Astronomical Observatory: JIANG Xiao-jun, XU Da-wei & HU Jing-yao Beijing Astronomical Observatory, CAS, Beijing 100080

NIGHT-SKY HIGH-RESOLUTION SPECTRAL ATLAS OF OH EMISSION LINES FOR ECHELLE SPECTROGRAPH WAVELENGTH CALIBRATION. II.

ABSTRACT The potential of night-sky emission lines recorded on every long-exposure astronomical spectrum, for wavelength calibration, is reemphasized. The previously published high-resolution atlas, based on spectra obtained with the Keck 10-meter telescope on Mauna Kea and the HIRES high-resolution echelle spectrograph, is extended from 9000 Å to 10600 Å, the present effective long-wavelength limit for reasonable exposure times with current CCD's. The extension of the atlas shows many OH night-sky lines, and makes it possible to identify them easily on high-resolution spectra. Accurate wavelengths and references to their sources are given. Measured intensity ratios for the resolved, well measured lambda-type doublets are presented, and the probable errors in the listed wavelengths of the unresolved doublets, based on them, are discussed. Observations and identifications of a number of lines of weak satellite or intecombination bands of OH in the night-sky spectrum are discussed, and the "not proven" result of a search for OH lines in the (10 - 5) and (10 - 4) bands is mentione.

SKY SPECTRA AT A LIGHT-POLLUTED SITE AND THE USE OF ATOMIC AND OH SKY EMISSION LINES FOR WAVELENGTH CALIBRATION

ABSTRACT Spectra of the night sky, taken at Lick Observatory in 1988 and 1989 as byproducts of nebular spectra, show the great increase of light pollution by sodium high-pressure and low-pressure lamps in comparison with previous spectra taken in 1975. The usefulness of the emission lines of the night sky spectrum for wavelength calibration is mentioned. In the far red and near-infrared regions, where there are only few atomic night-sky lines, the OH variation-rotation spectrum may be used for this purpose. Accurate rest wavelengths for these lines, calculated from the best laboratory determinations are tabulated, and the special suitability of the P1 (and to a lesser extent P2) lines are discussed.

Auroral and airglow observations using a grating spectrometer with an imaging photon detector

During December 1983 and the winter 1984-5, a grating spectrometer of 600 mm focal length and 150 mm grating width was equipped with an imaging photon detector (IPD) and used to observe night-sky spectra from two observational sites in Sweden, Kiruna (68 degrees N, an auroral station) and Stockholm (59 degrees N, a mid-latitude station). The data taken included sequences of spectra of the night sky from 300 to 700 nm. The instrument design and modifications to accommodate the imaging photon detector for the spectrometer application are discussed with the presentation of some preliminary results. The instrument makes it possible to obtain rapid time resolution of the behaviour of important but faint airglow and auroral spectral emissions which were previously only observable by integrating for several hours. It is also possible to obtain one dimension of spatial information along the direction of the spectrometer slit. This is of use, for example, when investigating the height-dependent spectroscopic structure of auroral arcs or spectral variations along the meridian.

Observation of Rayleigh scattering and airglow

A steerable 0.25-m Ebert monochromator and photomultiplier detector were employed to measure the spectra of the clear daytime sky (Rayleigh scattering). The day sky intensity as a function of wavelength was observed to vary as λ−4 in agreement with Rayleigh’s predictions and observations. The same monochromator and detector with the addition of a multichannel scaler were used to observe the night sky spectra (airglow). The oxygen (OI) emission at 557.7 nm was observed from the ground by using this technique.

Extreme Ultraviolet Spectrometer for Space Research

A normal incidence spectrometer for use in the wavelength region from 200 A to 1270 A has been developed. The design and calibration of the instrument are described in detail. The spectrometer can be employed to detect extreme uv radiation at a minimum flux level of 1 rayleigh with a spectral resolution of 40 A and a spatial resolution of 6 degrees . Data on the extreme uv night sky spectrum between 780 A and 1270 A obtained with this instrument on a recent rocket flight are presented.

MgI Emission in the Night Sky Spectrum

DURING September, October 1971 and April 1972 we observed a narrow region of the night sky spectrum in the vicinity of the 5183.62 A MgI wavelength. Measurements were made with a scanning Fabry-Perot interferometer1,2 from the observatory at Izana on Tenerife, Canary Islands, and consisted of spectral scans of up to 4 A wide centred on the MgI wavelength. In all, some 350 spectra were obtained. Because the primary aim of the experiment was to study the zodiacal light, all spectra were recorded between evening and morning twilights, and most in the ecliptic plane. None was recorded during twilight.

Radial velocity and intensity measurements of the night sky Hβ emission line

Observations of the Hβ emission line in the night sky spectrum are presented. The measurements were made with a gas pressure-scanned Fabry Perot Interferometer from Testa Grigia (11,500 ft) in the Italian Alps, in November and December, 1967. Typical emission rates measured were 0.1–0.2 Rayleighs ( R) and the line was found to be Doppler-shifted from the 4861.33 Å laboratory wavelength. The intensities and radial velocities of the Une are examined in various co-ordinate systems and it is shown that the total emission is probably due to the addition of two components; a ‘galactic’ and a ‘non-galactic’ contribution. The galactic contribution, due to nebular emission, dominates within ±15° latitude of the Milky Way; the emission at galactic latitudes greater than ±15° is interpreted as being non-galactic in origin and is discussed briefly in terms of both geocoronal and interplanetary emitting regions.

THE NEAR INFRARED SPECTRUM OF THE NIGHT AIRGLOW OBSERVED FROM HIGH ALTITUDE

The infrared emission spectrum of the upper atmosphere between 1.2 and 2.5 microns has been measured at night by means of a Michelson interferometer carried to an altitude of 90,000 feet by a balloon. The complete Δν = 2 sequence of rotation–vibration OH bands has been observed at a resolution sufficient to resolve the rotational structure. The (0, 0) band of the electronic transition [Formula: see text] of oxygen at 1.27 microns has been observed in the night-sky spectrum for the first time. Its brightness is comparable with that of the (4, 2) OH band at 1.6 microns.

Photometric observation of an artificial aurora

On July 9, 1962, at 9h 00m 09s GMT the United States detonated a nuclear device approximately two hundred miles above Johnston Island. A few seconds after the detonation a brilliant artificial aurora was observed over New Zealand, approximately four thousand miles distant. At this time the Physics Department of the University of Canterbury had in operation at its field station near Christchurch an airglow photometer, which recorded the intensities of the O I emissions, λ5577 and λ6300; and N2+ emission, λ4278, during the display. The photometer in use employs interference filters between 20 A and 30 A wide for separating out the desired parts of the night sky spectrum, switching from one emission to the next each twenty seconds. The optics of the photometer are arranged to balance out most of the continuum, so that only line or band emission within the passband of the interference filters is recorded.

Spectroscopic observations of the night sky in the extreme ultraviolet

An ƒ/1.5 spectrograph was flown twice in a rocket from White Sands to photograph the night sky spectrum from 1150 to 1630 Å. In each case, as the rocket spun and precessed, an integrated spectrum was obtained from all directions, including the earth below. The Lymanα emission was detected, but no other line radiation stronger than 4×10 −4erg sec −1 cm −2 sterad −1 nor any continuum radiation stronger than 2×10 −5erg sec −1 cm −2 sterad −1 Å −1 was found.

THE NIGHT-SKY SPECTRUM λλ 5000-6500 A.

view Abstract Citations (29) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS THE NIGHT-SKY SPECTRUM λλ 5000-6500 A. Blackwell, D. E. ; Ingham, M. F. ; Rundle, H. N. Abstract The paper describes a spectrum of the night sky obtained at the cosmic-ray station of Chacaltaya (latitude - 16 , height 17100 feet) at zenith distance 840, using a dispersion of 78 A/mm The spectrum is unusually intense, and in the region XX 5577-6500 fifty-one OH emission lines (some of which are multiple) are identified; the spin doubling of many lines is clearly resolved. A comparison between observed frequencies and frequencies calculated by means of newly derived band origins and rotational constants is given Rotational temperatures are determined, and the absolute intensities of OH lines and the N I emission at X 5199 have been measured The fine structure of the OH emission in the region of Ha is calculated Publication: The Astrophysical Journal Pub Date: January 1960 DOI: 10.1086/146801 Bibcode: 1960ApJ...131...15B full text sources ADS |