Flagstaff, AZ, United States
Flagstaff, AZ, United States

Time filter

Source Type

Luginbuhl C.B.,Us Naval Observatory Flagstaff Station | Boley P.A.,Max Planck Institute for Astronomy | Davis D.R.,Planetary Science Institute | Duriscoe D.M.,National Park Service
Proceedings of the International Astronomical Union | Year: 2012

Using a wavelength-generalized version of the Garstang (1991) model, we evaluate overhead sky glow as a function of distance up to 300 km, from a variety of lamp types, including common gas discharge lamps and several types of LED lamps. We conclude for both professional, and especially cultural (visual), astronomy, that low-pressure sodium and narrow-spectrum amber LED lamps cause much less sky glow than all broad-spectrum sources. © 2015 International Astronomical Union.

Carter W.E.,University of Florida | Carter M.S.,Us Naval Observatory Flagstaff Station
Journal of Navigation | Year: 2010

This paper examines the evidence to support the view that the inability of seamen to determine accurate longitude at sea in sailing ships was a major factor in the loss of ships and crews that was effectively solved by the introduction of the marine chronometer. It concludes that this was not the case and that a more compelling factor for the safety of ships was the introduction of mechanical propulsion systems. © 2010 The Royal Institute of Navigation.

Zdanavicius J.,Vilnius University | Vrba F.J.,Us Naval Observatory Flagstaff Station | Zdanavicius K.,Vilnius University | Straizys V.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group
Baltic Astronomy | Year: 2011

We present the results of eight-color CCD photometry of 674 stars in the direction of the open cluster Tombaugh 5 in Camelopardalis. The stars are observed in the Vilnius system supplemented by the broad-band I filter; the field is of 22' diameter, the limiting magnitude is V = 17.7 mag. The catalog contains the coordinates, V magnitudes, seven color indices, two-dimensional spectral types determined from photometric parameters, interstellar extinctions and distances. The color-magnitude diagram plotted for 480 individually dereddened stars is used to identify cluster members and to determine the distance (1.74 kpc) and age (200-250 Myr) of the cluster. The faintest cluster stars classified are of spectral class G0. The cluster contains two blue stragglers of spectral classes B2-B4, both of them seem to be visual binaries. The extinction A V for the cluster stars is non-uniform, being spread between 2 and 3 mag, with a mean value of 2.42 mag. The extinction vs. distance dependence can be modeled by the Parenago exponential curve with two dust concentrations in the Camelopardalis dark clouds at about 150 pc and the Cam OB1 association clouds at 0.9-1.0 kpc.

Straizys V.,Vilnius University | Milasius K.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Vrba F.J.,Us Naval Observatory Flagstaff Station | And 8 more authors.
Astronomical Journal | Year: 2014

Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of the cluster in the Vilnius seven-color photometric system, supplementing it with available data in the BV and JHKs photometric systems and spectra of the nine brightest stars of spectral classes O and B. Photometric spectral classes and luminosities of 260 stars in a 15′ x 15′ area down to V = 19 mag are used to investigate the interstellar extinction run with distance and to estimate the distance of the Great Cygnus Rift, ∼ 800 pc. The interstellar reddening law in the optical and near-infrared regions is found to be close to normal, with the ratio of extinction to color excess RBV = 2.87. The extinction AV of cluster members is between 2.5 and 3.8 mag, with a mean value of 2.97 mag, or EB-V = 1.03. The average distance of eight stars of spectral types O9-B2 is 1.54 ± 0.15 kpc. Two stars from the seven brightest stars are field stars: HDE 229238 is a background B0.5 supergiant and HD 194378 is a foreground F star. In the intrinsic color-magnitude diagram, seven fainter stars of spectral classes B3-B8 are identified as possible members of the cluster. The 15 selected members of the cluster of spectral classes O9-B8 plotted on the log L/L⊙ versus log Teff diagram, together with the isochrones from the Padova database, give the age of the cluster as 5 ± 1 Myr. © 2014. The American Astronomical Society. All rights reserved.

Zdanavicius J.,Vilnius University | Bartasiute S.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Vrba F.J.,Us Naval Observatory Flagstaff Station | Zdanavicius K.,Vilnius University
Baltic Astronomy | Year: 2010

CCD photometry in the eight-color Vilnius + I system for 7250 stars down to I = 19.6 mag has been obtained in the 20′ x 26′ field of the open cluster IC 361 in Camelopardalis. The catalog of 1420 stars down to V ∼ 18.5 mag is presented. It contains the coordinates, V magnitudes and seven color indices, quantitative photometric spectral types, absolute magnitudes and distances. The interstellar extinction is found to be non-uniform across the field, with the values of AV in the range 1.9 to 2.4 mag. The distribution of distance moduli of individual stars shows that the cluster is located as far as, or just beyond, the Perseus spiral arm.

Lazio T.J.W.,NASA | Lazio T.J.W.,U.S. Navy | Lazio T.J.W.,Jet Propulsion Laboratory | Shankland P.D.,Us Naval Observatory Flagstaff Station | And 2 more authors.
Astronomical Journal | Year: 2010

This paper reports Very Large Array observations at 325 and 1425 MHz (λ90 cm and λ20 cm) during and near the periastron passage of HD 80606b on HJD 2454424.86 (2007 November 20). We obtain flux density limits (3σ) of 1.7mJy and 48μJy at 325 and 1425 MHz, respectively, equivalent to planetary luminosity limits of 2.3×1024 erg s-1 and 2.7 × 1023 erg s-1. Unfortunately, these are several orders of magnitude above the nominal Jovian value (at 40 MHz) of 2×10 18 erg s-1. The motivation for these observationswas that the planetarymagnetospheric emission is driven by a stellarwind- planetarymagnetosphere interaction so that the planetary luminositywould be elevated near periastron.We estimate that, near periastron,HD80606b might be as much as 3000 times more luminous than Jupiter. Recent transit observations of HD 80606b provide reasonably stringent constraints on the planetarymass and radius, and, because of the planet's highly eccentric orbit, its rotation period is likely to be "pseudo-synchronized" to its orbital period, allowing a robust estimate of the former. Consequently,we are able tomake relatively robust estimates of the emission frequency of the planetary magnetospheric emission and find it to be around 60-90 MHz. While this is too low for our reported observations, we compare HD 80606b to other high-eccentricity systems and assess the detection possibilities for both near-term and more distant future systems. Of the known high-eccentricity planets, only HD 80606b is likely to be detectable, as the others (HD 20782B and HD 4113) are both lower mass and longer rotational periods, which imply weaker magnetic field strengths. We find that both the forthcoming "EVLA low band" system, which will operate as low as 65 MHz, and the Low Frequency Array may be able to improve upon our planetary luminosity limits forHD80606b, and do so at amore optimum frequency. If the low-frequency component of the Square Kilometre Array (SKA-lo) and a future lunar radio array are able to approach their thermal noise limits, they should be able to detect an HD 80606b-like planet, unless the amount by which the planet's luminosity increases is substantially less than the factor of 3000 that we estimate; for the SKA-lo, which is to be located in the southern hemisphere, future planetary surveys will have to find southern hemisphere equivalents of HD 80606b. © 2010. The American Astronomical Society. All rights reserved.

Duriscoe D.M.,National Park Service | Luginbuhl C.B.,Us Naval Observatory Flagstaff Station | Elvidge C.D.,National Oceanic and Atmospheric Administration
Lighting Research and Technology | Year: 2014

Five cities in the southwest United States were selected for an analysis of the impact of outdoor lighting practices on nighttime sky glow as observed from distances of 8-67 km. Data from the Suomi National Polar-orbiting Partnership (NPP) satellite visible infrared imaging radiometer suite day/night band were used to identify light sources for input to an atmospheric sky glow model. Total lumens of outdoor lighting were estimated by matching modelled to observed anthropogenic sky luminance at ground locations. The results of two conservative treatments were then modelled for each city: all outdoor luminaires fully shielded with the current lumen amount, and fully shielded luminaires with a lumen amount scaled to 2075 lm capita-1, matching Flagstaff, Arizona. The results indicate 42-88% reductions in average all-sky glow utilizing these 'best practices' for environmental conservation. © 2013 The Chartered Institution of Building Services Engineers.

Armstrong J.T.,U.S. Navy | Schmitt H.R.,U.S. Navy | Mozurkewich D.,Seabrook Engineering | Jorgensen A.M.,New Mexico Institute of Mining and Technology | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The Navy Precision Optical Interferometer (NPOI) was designed from the beginning to support baseline boot-strapping with equally-spaced array elements. The motivation was the desire to image the surfaces of resolved stars with the maximum resolution possible with a six-element array. Bootstrapping two baselines together to track fringes on a third baseline has been used at the NPOI for many years, but the capabilities of the fringe tracking software did not permit us to bootstrap three or more baselines together. Recently, both a new backend (VISION; Tennessee State Univ.) and new hardware and firmware (AZ Embedded Systems and New Mexico Tech, respectively) for the current hybrid backend have made multi-baseline bootstrapping possible. © 2014 SPIE.

Straizys V.,Vilnius University | Vrba F.J.,Us Naval Observatory Flagstaff Station | Boyle R.P.,Vatican Observatory Research Group | Milasius K.,Vilnius University | And 6 more authors.
Astronomical Journal | Year: 2015

The interstellar extinction is investigated in a 1.5 deg2 area in the direction of the open cluster M29 (NGC 6913) in Cygnus, centered at R.A. = 20h 24m, decl. = +38° 30′. The study is based on photometric classification of 1110 stars in spectral and luminosity classes down to V = 19 mag using photometry in the Vilnius seven-color system published in Paper I (Milašius et al. 2013). Additionally, in the same area the extinction is investigated using 1147 red clump giants (RCGs), identified by combining selected two-color diagrams of the 2MASS and Spitzer surveys. The investigated area is divided into three parts with different obscuration and in these directions the extinction versus distance plots up to 5 kpc are presented. In the whole area a steep rise of the extinction is observed at a distance of ∼800 pc; it should be related to dust clouds in the Great Cygnus Rift obscuring the stars behind it by AV = 4.0-4.7 mag. RCGs exhibit much larger extinction values, up to = 1.2-1.3 mag in the more transparent areas and 1.45 mag in the northeastern part of the area and above it, where the dust cloud TGU H466 is located. These values of correspond to AV = 10-12 mag. We do not exclude the possibility that the largest values of the extinction belong not to RCGs but to some contaminating intrinsically red AGB stars penetrated through the applied RCG selection constraints. The extinction in the TGU H466 cloud probably originates in two cloud systems - the Great Cygnus Rift at 800 pc and the Cygnus X complex of dust and molecular clouds at 1.3-1.5 kpc. © 2015. The American Astronomical Society. All rights reserved..

Luginbuhl C.B.,Us Naval Observatory Flagstaff Station | Boley P.A.,Dark Sky Partners LLC | Davis D.R.,Dark Sky Partners LLC
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2014

The effect of light source spectral power distribution on the visual brightness of anthropogenic sky glow is described. Under visual adaptation levels relevant to observing the night sky, namely with dark-adapted (scotopic) vision, blue-rich ("white") sources produce a dramatically greater sky brightness than yellow-rich sources. High correlated color temperature LEDs and metal halide sources produce a visual brightness up to 8× brighter than low-pressure sodium and 3× brighter than high-pressure sodium when matched lumen-for-lumen and observed nearby. Though the sky brightness arising from blue-rich sources decreases more strongly with distance, the visual sky glow resulting from such sources remains significantly brighter than from yellow sources out to the limits of this study at 300. km. © 2014 The Authors.

Loading Us Naval Observatory Flagstaff Station collaborators
Loading Us Naval Observatory Flagstaff Station collaborators