This page allow to get acquired LPMD values for all defined stations.
Simply select date parameters and submit your request.
Main sky brigthness value is provided in Magnitude per square arcsecond (MPSAS)
MPSAS numbers are commonly used in astronomy to measure sky darkness (higher value means darker).
We can also express this value in NELM (Naked Eyes Limiting Magnitude) which roughly indicates human eyes visibles stars limit.
A +1 magnitude means 2.5 times less light is coming from a given area of sky.
A 5 mags/sq arcsec change means a 100x darker or brighter sky.
Common values and interpretation
|Typical values||Location type|
|Over 22||best theorical dark sky reacheable on earth|
|22.0 mpsas||a moonless night sky that's completely free of artificial light pollution|
|21.0 mpsas||a rural area with a medium-sized city not far away|
|20.0 mpsas||suburbs of a major metropolis. Summer Milky Way is visible but severely washed out|
|19.0 mpsas||suburb with widely spaced single-family homes|
|18.0 mpsas||a bright suburb or dark urban neighborhood|
|17.0 mpsas||a typical sky near the center of a major city.|
|13.0 mpsas||zenith skyglow at the end of civil twilight, Venus and Jupiter are easy to see, but bright stars are just beginning to appear|
|7.0 mpsas||zenith skyglow at sunrise or sunset|
Some average or duration computation are made with >= 13 MPSAS values (considered as 'local night' after civil twilight)
Sky observation duration computation are made with >= 19 MPSAS values (considered as 'good night condition')
Data recording is gnerally executed on a 5 min period (but could be ajusted for some studies), send to a central database synchronized each day.
Due to (a lot) of circumstancies (power failure, internet povider failure, lack of connectivity), LPMD can capture information but be outside any internet connexion.
In this case, he will continues to acquire measures if possible, and a synchronization will occurs when network and connectivity comes back alive (generally after a software, or sometines physical, planned or forced reboot).
At this time, deployed LPMD status (and last read value) are :
Green : LPMD box is alive and connected
Orange : LPMD box is alive, but temporarely disconnected from network
Red : LPMD box status is indetermined (but recording continues locally outside power failure case)
Several data views (by year, month or day) could be extracted on request
Please select date parameters and ask for a view
Three available duration filters starts :
Data extraction will be executed from start date at 12:00:00 till end date at 12:00:00, and all computation made on night period duration.
Important Remark : this LPMD is in permanent evolution, some data file aspects (like detection or start/end period) could vary