A Sky Brightness Contrast Measurement before Sunrise and after Sunset over a Baghdad Region, Iraq

High school cosmetology students study the methods and effects of various human hair treatments, including permanents, straightening, conditioning, coloring and cutting. Although they are provided with textbook examples of overtreatment and numerous hair disorders and diseases, a view of an individual hair at the high resolution offered by an SEM provides convincing evidence of the hair‘s altered structure. Magnifications up to 2000X provide dramatic differences in perspective. A good quality classroom optical microscope can be very informative at lower resolutions.Students in a cosmetology class are initially split into two groups. One group is taught basic controls on the SEM (focus, magnification, brightness, contrast, specimen X, Y, and Z axis movements). A healthy, untreated piece of hair is initially examined on the SEM The second group cements a piece of their own hair on a stub. The samples are dryed quickly using heat or vacuum while the groups trade places and activities.

Download Full-text

Effect of diffuse sky brightness on the spectrophotometry of rough Martian surfaces

Journal of Geophysical Research Atmospheres ◽

10.1029/1999je001222 ◽

2000 ◽

Vol 105 (E11) ◽

pp. 26739-26744 ◽

Cited By ~ 1

Author(s):

Nicolas Thomas

Keyword(s):

Sky Brightness

Download Full-text

EFFECTS OF AGE AND BRIGHTNESS CONTRAST ON PERCEPTION OF THE WUNDT-HERING ILLUSION

Perceptual and Motor Skills ◽

10.2466/pms.71.6.427-431 ◽

1990 ◽

Vol 71 (6) ◽

pp. 427 ◽

Cited By ~ 2

Author(s):

EILEEN ASTOR-STETSON

Keyword(s):

Brightness Contrast

Download Full-text

Effects of the COVID-19 Lockdown on Urban Light Emissions: Ground and Satellite Comparison

Remote Sensing ◽

10.3390/rs13020258 ◽

2021 ◽

Vol 13 (2) ◽

pp. 258

Author(s):

Máximo Bustamante-Calabria ◽

Alejandro Sánchez de Miguel ◽

Susana Martín-Ruiz ◽

Jose-Luis Ortiz ◽

José M. Vílchez ◽

...

Keyword(s):

Economic Activity ◽

Primary Source ◽

Clear Correlation ◽

Light Pollution ◽

Nocturnal Activity ◽

Empirical Expression ◽

Anthropogenic Aerosol ◽

The Earth ◽

Sky Brightness ◽

The City

‘Lockdown’ periods in response to COVID-19 have provided a unique opportunity to study the impacts of economic activity on environmental pollution (e.g., NO2, aerosols, noise, light). The effects on NO2 and aerosols have been very noticeable and readily demonstrated, but that on light pollution has proven challenging to determine. The main reason for this difficulty is that the primary source of nighttime satellite imagery of the earth is the SNPP-VIIRS/DNB instrument, which acquires data late at night after most human nocturnal activity has already occurred and much associated lighting has been turned off. Here, to analyze the effect of lockdown on urban light emissions, we use ground and satellite data for Granada, Spain, during the COVID-19 induced confinement of the city’s population from 14 March until 31 May 2020. We find a clear decrease in light pollution due both to a decrease in light emissions from the city and to a decrease in anthropogenic aerosol content in the atmosphere which resulted in less light being scattered. A clear correlation between the abundance of PM10 particles and sky brightness is observed, such that the more polluted the atmosphere the brighter the urban night sky. An empirical expression is determined that relates PM10 particle abundance and sky brightness at three different wavelength bands.

Download Full-text

Reanalysis of the 1992 South Pole Millimetre-Wavelength Atmospheric Opacity Data

Publications of the Astronomical Society of Australia ◽

10.1071/as03012 ◽

2004 ◽

Vol 21 (3) ◽

pp. 264-274 ◽

Cited By ~ 8

Author(s):

Richard A. Chamberlin

Keyword(s):

Time Series ◽

Transfer Model ◽

South Pole ◽

Millimetre Wave ◽

Atmospheric Opacity ◽

Site Survey ◽

Direct Measurements ◽

Gain Error ◽

Sky Brightness ◽

Total Opacity

AbstractIn 1992 an NRAO 225-GHz site survey heterodyne radiometer was placed at the Geographical South Pole. The instrument operated over an entire annual cycle and provided direct measurements of the millimetre-wave sky brightness temperature as a function of zenith angle. Interpreted in a single-slab ‘skydip’ radiation transfer model of the atmosphere, these sky brightness measurements provided a time series of the millimetre atmospheric opacity. Statistics derived from this opacity time series were important for making comparisons with other candidate millimetre and sub-millimetre wave astronomy sites. This paper reexamines the 1992 measurements and the original analysis. Details of the skydip fit model, radiometer gain error, instrument stability, and a mid-season replacement to a window in the instrument enclosure combined to cause a modest under-reporting of the atmospheric opacity in previous reports. Unchanged are earlier conclusions that dry air makes a significant contribution to the total opacity at 225 GHz.

Download Full-text

Worldwide variations in artificial skyglow

Scientific Reports ◽

10.1038/srep08409 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 79

Author(s):

Christopher C. M. Kyba ◽

Kai Pong Tong ◽

Jonathan Bennie ◽

Ignacio Birriel ◽

Jennifer J. Birriel ◽

...

Keyword(s):

Monitoring Program ◽

Artificial Light ◽

Clear Sky ◽

International Monitoring ◽

Sky Brightness ◽

Ground Truthing ◽

Study Sites ◽

Night Sky Brightness ◽

Key Questions

Abstract Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.

Download Full-text

Illusory Reversal of Brightness Contrast

Perceptual and Motor Skills ◽

10.2466/pms.1968.27.3f.1169 ◽

1968 ◽

Vol 27 (3_suppl) ◽

pp. 1169-1170 ◽

Cited By ~ 2

Author(s):

Whitman Richards

Keyword(s):

Visual System ◽

Visual Angle ◽

Low Frequency ◽

Brightness Contrast ◽

Linear Behavior ◽

Non Linear

An illusion analogous to Cornsweet's is used to demonstrate how the non-linear behavior of the visual system can be used to obscure low-frequency gradients. The result is a reversal of brightness—from light to dark—as the visual angle of the display is changed.

Download Full-text