Night Sky Quality Monitoring Report

 

 

Hopewell Furnace NHS

Meadow south of Church House

16-Aug-2014

To effectively manage any resource, we need to know what we have and what we've lost. Light pollution, the brightness in the nighttime sky due to artificial light, effectively masks natural sources of light at night such  as the stars and the Milky Way. The NPS has developed a system for measuring sky brightness to quantifthe source and severity of light pollution. This system, developed with assistance from professional astronomers and the International DarkSky Association, uses a researchgrade digital camera to capture the entire sky with a series of images. Data clearly show that almost every park, even remote national parks, are not immune from stray artificial light. Sky brightness is measured in astronomical magnitudes in the visual band or Vband, abbreviated as "mags". The Vband measures mostly green light, omitting purple through ultraviolet and orange through infrared. The magnitude scale is a logarithmic scale. A difference of 5 magnitudes corresponds to a 100x difference in brightness. Lower values (smaller or more negative) are brighter. Further information on astronomical magnitudes can be found on this Sky and Telescope webpage. Data images are shown in false color, with yellow, red, and white corresponding to brighter sky and blue, purple and black corresponding to darker sky.

 

A more detailed explanation is available.

 

 

Data Set Attributes and Visual Indicators

 

Category

Details

Observed and Estimated Artificial Sky Brightness Mosaics

Park:

Hopewell Furnace NHS

Click on either image for a high resolution view --THESE ARE LARGE FILES

Site Name:

Meadow south of Church House


Longitude:

-75.77

Latitude:

40.21

Elevation (m):

200

Date (LMT):

16-Aug-2014

Time (LMT Hours):

20.74

Camera:

ML4

Lens:

Nikon 1.2


Observers:

C Moore

Air temp. C):

17.8

R. H. (%):

77.0

Wind Speed (mph):

 

Extinction Coeff. (mag/airmass):

0.27

 

NELM:

5.5

Bortle Class:

5

Synthetic SQM:

19.87

SQI All- sky:

25.6

SQI to Z.A. 70°:

30.7

Number of stars visible:

1130

NARRATIVE:

 

 

 

 

Photometric Indicators

 

Indicator

Observed

Estimated Artificial

Light Pollution Ratio (Artificial/Natural)

Sky Luminance Measures

 

mag/ arscec2

μcd/ m2

mag/ arscec2

μcd/ m2

 

Zenith

20.23

876

20.45

707

4.13

Mean all-sky

19.04

2,629

19.13

2,388

9.62

Brightest

16.84

19,727

16.85

19,538

114.26

Darkest

20.22

871

20.44

711

4.16

Median

19.42

1,832

19.57

1,585

6.34

Illuminance Measures

 

mags

milli-lux

mags

milli-lux

 

Horizontal

-8.37

5.64

-8.22

4.90

6.13

Max Vertical

-8.44

6.03

-8.35

5.55

13.88