Measuring the visual limiting magnitudite with naked eye
by Lorenzo Comolli

Many are the methods available to measure the limiting magnitude with naked eye. Each of them can produce significantly different results, and in many years of experience I've selected one of them that proved to give quite reliable values.
The method is quite simple:
  • first, download and print the table and map below, with stars from a location around the North celestial pole, so that it's observable all over the year from the northern hemisphere
  • under a dark sky, find a confortable place, such as a deckchair, and point it toward Polaris
  • use only very weak and red lights: you should only barely be able to read the star map
  • start searching the brightest stars and check them on the table
  • stop when you cannot find any of the faintest stars, even after a very accurate search that can require many minutes of trials

Click the image to download the PDF table and map.

Some example of my measurements:
SQM-L at zenith
Limiting magnitude
Bogli (PC), Italian Appennines, 1350 m
5 July 2008, 23 UT
Very clear and transparent night; using my "super-glasses" able to add a full diopter to normal glasses.
Same as above but without "super-glasses", only with my "astronomical" glasses (-0.5) that were quite old and my eyesight was not fully corrected
Colle dell'Agnello (CN), Italian Alps, 2700 m
21 August 2009, 23 UT
Very clear and transparent night; using my new "astronomical" glasses plus "super-glasses"
Only "astronomical" glasses (-0.75)

For any comment, send me an e-mail:

HTML Editing and Publishing by Lorenzo Comolli. Email me at
Back to Main Page