Of Beaufort and Bortle …

Sir Francis Beaufort (1774-1875) a British Naval Commander, later Admiral, devised a scale by which to record wind strength. It was initially for use at sea based on observational characteristic. It ranged from 0 -Calm to 12-Hurricane and, for example at force 3-Gentle Breeze wave crests begin to break. It was adapted for use on land correlated with other observational criteria. I can remember some representative wind strengths from my scouting days :-

  • 3 Gentle Breeze – Girl Guide’s skirt begins to rustle.
  • 6 Strong Breeze – glimpse of under wear
  • 8 Gale – skirt over Girl Guide’s head
  • 10 Whole Gale – Girl Guide stripped naked
  • 12 Hurricane – retrieve Girl Guides from treetops later

In 2001 John E. Bortle came up with an observational scale to record light pollution in the night sky. Bortle 1 is a dark sky with no light pollution, Bortle 9 is an inner city sky where only the moon, planets and a few bright stars are visible. It is based on observations that anyone can make such as whether you can see M15, M4, M5, and M22 with the naked-eye which would be a Bortle 3 – Rural Sky. ( I personally have never seen these but I believe there may be an overpass just north of London where you can see all of them from one vantage point).

Most humans live in cities and unless you live in North Korea the nearest dark sky is quite a drive away. I live in a Bortle 2 area but being in other ways a typical human I hankered for something more. My trip to the desert was made while the moon was but a waning crescent in order to bask in the glow of a Bortle 1. And of course there was only a short break in the clouds on the first night.

The second night found me in the Little Desert contemplating Grass Trees (Xanthorrhoea sp.) and looking for M22 where M stands for Messier

also known as NGC 6656, is an elliptical globular cluster of stars in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars that is visible in the night sky. The brightest stars are 11th magnitude, with hundreds of stars bright enough to resolve with an 8″ telescope. M22 is located just south of the Ecliptic, and northwest of Lambda Sagittarii (Kaus Borealis), the northernmost star of the “Teapot” asterism (Wikipedia)

It may be in the photos. If you find it please let me know.

 

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.