The scale doesn't seem right to me. I have been in extremely dark areas, no light pollution, with enough starlight to walk without a flashlight. -- Joe ________________________________ From: Jay Eads <jayleads@gmail.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Friday, May 10, 2013 12:40 PM Subject: [Utah-astronomy] Bortle Scale Here is an article from Sky  & Telescope on the Bortle System. http://www.skyandtelescope.com/resources/darksky/3304011.html You can use a SQM and the following formula to determine the NELM of a site. Take the reading (the site out by Vernon averages 21.7 to 22.0, and subtract 8.8, divide by 2 and add .5 and you'll have a very close reading to the NELM of the site depending on the average.  The Vernon site we use is around 6.9 to 7.0 depending on the season.  I would assume SPOC would come in around 6.6 or so. The problem with the Bortle System and NELM is it can vary based on the observer and their experience, age and condition of their eyes. _______________________________________________ Utah-Astronomy mailing list http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Send messages to the list to Utah-Astronomy@mailman.xmission.com The Utah-Astronomy mailing list is not affiliated with any astronomy club. To unsubscribe go to: http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Then enter your email address in the space provided and click on "Unsubscribe or edit options".