58 research outputs found
Using all-sky differential photometry to investigate how nocturnal clouds darken the night sky in rural areas
Artificial light at night has affected most of the natural nocturnal
landscapes worldwide and the subsequent light pollution has diverse effects on
flora, fauna and human well-being. To evaluate the environmental impacts of
light pollution, it is crucial to understand both the natural and artificial
components of light at night under all weather conditions. The night sky
brightness for clear skies is relatively well understood and a reference point
for a lower limit is defined. However, no such reference point exists for
cloudy skies. While some studies have examined the brightening of the night sky
by clouds in urban areas, the published data on the (natural) darkening by
clouds is very sparse. Knowledge of reference points for the illumination of
natural nocturnal environments however, is essential for experimental design
and ecological modeling to assess the impacts of light pollution. Here we use
differential all-sky photometry with a commercial digital camera to investigate
how clouds darken sky brightness at two rural sites. The spatially resolved
data enables us to identify and study the nearly unpolluted parts of the sky
and to set an upper limit on ground illumination for overcast nights at sites
without light pollution.Comment: 17 pages, 6 figure
Measuring Light Pollution with Fisheye Lens Imagery from A Moving Boat, A Proof of Concept
Near all-sky imaging photometry was performed from a boat on the Gulf of
Aqaba to measure the night sky brightness in a coastal environment. The boat
was not anchored, and therefore drifted and rocked. The camera was mounted on a
tripod without any inertia/motion stabilization. A commercial digital single
lens reflex (DSLR) camera and fisheye lens were used with ISO setting of 6400,
with the exposure time varied between 0.5 s and 5 s. We find that despite
movement of the vessel the measurements produce quantitatively comparable
results apart from saturation effects. We discuss the potential and limitations
of this method for mapping light pollution in marine and freshwater systems.
This work represents the proof of concept that all-sky photometry with a
commercial DSLR camera is a viable tool to determine light pollution in an
ecological context from a moving boat.Comment: 9 pages, 6 figures, accepted at International Journal of Sustainable
Lightin
Evaluating the summer night sky brightness at a research field site on Lake Stechlin in northeastern Germany
We report on luminance measurements of the summer night sky at a field site
on a freshwater lake in northeastern Germany (Lake Stechlin) to evaluate the
amount of artificial skyglow from nearby and distant towns in the context of a
planned study on light pollution. The site is located about 70 km north of
Berlin in a rural area possibly belonging to one of the darkest regions in
Germany. Continuous monitoring of the zenith sky luminance between June and
September 2015 was conducted utilizing a Sky Quality Meter. With this device,
typical values for clear nights in the range of 21.5-21.7
magarcsec were measured, which is on the order of the natural sky
brightness during starry nights. On overcast nights, values down to 22.84
magarcsec were obtained, which is about one third as bright as on
clear nights. The luminance measured on clear nights as well as the darkening
with the presence of clouds indicate that there is very little influence of
artificial skyglow on the zenith sky brightness at this location. Furthermore,
fish-eye lens sky imaging luminance photometry was performed with a digital
single-lens reflex camera on a clear night in the absence of moonlight. The
photographs unravel several distant towns as possible sources of light
pollution on the horizon. However, the low level of artificial skyglow makes
the field site at Lake Stechlin an excellent location to study the effects of
skyglow on a lake ecosystem in a controlled fashion.Comment: 20 pages, 8 figures, Journal of Quantitative Spectroscopy and
Radiative Transfer 201
Imaging and mapping the impact of clouds on skyglow with all-sky photometry
Artificial skyglow is constantly growing on a global scale, with potential
ecological consequences ranging up to affecting biodiversity. To understand
these consequences, worldwide mapping of skyglow for all weather conditions is
urgently required. In particular, the amplification of skyglow by clouds needs
to be studied, as clouds can extend the reach of skyglow into remote areas not
affected by light pollution on clear nights. Here we use commercial digital
single lens reflex cameras with fisheye lenses for all-sky photometry. We track
the reach of skyglow from a peri-urban into a remote area on a clear and a
partly cloudy night by performing transects from the Spanish town of Balaguer
towards Montsec Astronomical Park. From one single all-sky image, we extract
zenith luminance, horizontal and scalar illuminance. While zenith luminance
reaches near-natural levels at 5km distance from the town on the clear night,
similar levels are only reached at 27km on the partly cloudy night. Our results
show the dramatic increase of the reach of skyglow even for moderate cloud
coverage at this site. The powerful and easy-to-use method promises to be
widely applicable for studies of ecological light pollution on a global scale
also by non-specialists in photometry.Comment: 13 pages, 7 figure
Imaging of trapped ions with a microfabricated optic for quantum information processing
Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2±1.5% was observed. The depth of focus for the imaging system was 19.4±2.4μm and the field of view was 140±20μm. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures
Stripe-array diode-laser in an off-axis external cavity: Theory and experiment
Stripe-array diode lasers naturally operate in an anti-phase supermode. This produces a sharp double lobe far field
at angles \$\pm \alpha\$ depending on the period of the array.
In this paper a 40 emitter gain guided stripe-array laterally coupled by off-axis filtered feedback is investigated
experimentally and numerically. We predict theoretically and confirm experimentally that at
doubled feedback angle \$2 \alpha\$ a stable higher order supermode exists with twice the number of emitters per array period.
The theoretical model is based on time domain traveling wave equations for optical fields coupled to the carrier density equation taking
into account diffusion of carriers. Feedback from the external reflector is modeled using Fresnel
integration
Assessing long-term effects of artificial light at night on insects: what is missing and how to get there
Widespread and significant declines of insect population abundances and biomass are currently one of the most pressing issues in entomology, ecology and conservation biology. It has been suggested that artificial light at night is one major driver behind this trend.
Recent advances in the gathering and analysis of long-term data sets of insect population and biomass trends, however, have mostly focused on the effects of climate change and agricultural intensification.
We posit here that adequate assessment of artificial night at light that would be required to evaluate its role as a driver of insect declines is far from trivial. Currently its implementation into entomological monitoring programmes and long-running ecological experiments is hampered by several challenges that arise due to (i) its relatively late appearance as a biodiversity threat on the research agenda and (ii) the interdisciplinary nature of the research field where biologists, physicists and engineers still need to develop a set of standardised assessment methods that are both biologically meaningful and easy to implement.
As more studies that address these challenges are urgently needed, this article aims to provide a short overview of the few existing studies that have attempted to investigate longer-term effects of artificial light at night on insect populations.
To improve the quality and relevance of studies addressing artificial light at night and its effect on insects, we present a set of best practise recommendations where this field needs to be heading in the coming years and how to achieve it
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