25 October 2013

Dark Sky Readings

Knightware is keenly aware that light pollution is ruining stargazing for observers around the world. Measuring the darkness of the sky is useful to many pursuits beyond the simple visual observer. Astro-imagers use the measurements to estimate exposures; biologists use them to study various affects on humans and animals. The importance of gathering such data is explained in last month's post, entitled 'Why is the Skyglow Observations Standard Format Important?'.

Gathering Readings Data Automatically

Knightware added a feature to its astronomy software entitled SQM Reader Pro 2 that sends readings acquired from the user's Sky Quality Meter to the Knightware website, knightware.biz. Sending readings to this webpage is optional, and the exact location of the meter is altered a small amount to protect the privacy of the contributor.

Send reading to Knightware

Displaying Readings Data

The contributed readings data are displayed on a Google Map for public viewing at http://www.knightware.biz/community/public/sqm2/sqm_map.php. In the month since the software was released, 14,000 readings have been contributed from 9 meter installation sites. The number of readings is high because some users are contributing data as often as once per minute. Others are contributing less frequently. Readings are only accepted when the sun is below the horizon at the location of the meter.

SQM Readings Map

Knightware has been working on back-end data management tools to keep the data 'cleaned up'. Work on these tools is nearly complete. One  problem that we've already seen is that sometimes readings are submitted for a single meter at multiple meter installations over a few days. A meter installation is defined as the meter serial number, latitude, longitude and time offset from GMT. That essentially describes the hardware and it's location, and it is represented on the map as a marker with a number on it. It looks like some users change the latitude and longitude of the meter slightly to refine it's position on the map. When this pattern is detected, Knightware can move all of the readings to the meter installation that seems to be the final, corrected one. If a user sees their contributed data condensed into one map marker, that's why.

The public map displays a marker for each meter installation with a number on it. The number indicates the last reading reported for the meter location with fractional digits truncated. By clicking on a marker, a user can see the date & time of the reading in both local and universal time, the reading data in both MPSAS and NELM, and the moon's altitude and phase. The mean and standard deviation of all readings received over the latest 12 months from the meter installation with the moon below the local horizon are also shown.
Meter Installation Detail
Once the back-end tools are complete, Knightware will begin working on other tools for licensed users that will allow them to view more details of their data. Requirements for these tools are being gathered now.


Knightware thanks all of the SQM Reader Pro 2 users that are contributing data to the Knightware website. The goal is to provide both a publicly accessible display of the data and a more in-depth display for licensed users.