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:
Click the image to download the PDF table and map.
Some example of my measurements:
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:
| Location |
Date |
Notes |
SQM-L at zenith [mag/arcsec^2] |
Limiting magnitude [mag] |
| 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. |
21.66 |
7.6 |
| 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 |
6.6 |
|||
| 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" |
21.79 |
7.3 |
| Only "astronomical" glasses (-0.75) |
6.8 |
