Counting Stars to Measure Light Polution

Discuss the greatest threat to amateur astronomy today

Moderators: joe, Brian, Guy Fennimore, JohnM

Post Reply

Did you find this topic useful?

Yes - This is a very useful topic
No - I didn't find this topic useful.
Total votes: 7

Posts: 4
Joined: Tue Nov 13, 2007 1:44 am
Location: Tampa, FL

Counting Stars to Measure Light Polution

Post by dream_mas »

I read that you can count the stars in your sky to measure the level of light polution you are experiencing. This makes sense but the article I read gave no basis for comparision.

I live in SouthWest Central Florida, Just below Tampa Bay, This past Friday, November 9th 2007, under a clear cool sky around 1am I counted 98 stars.

I am wondering where 98 stars would fall in measurement of light pollution based on star counting.

Any takers on this?
Dream Master "Master of My Dreams - Maker of Yours!"
TeleSTAR 60mm / 24-12.5-4mm pieces W/ 3x Barlow
Cyclops16A Epoch 515362811 - MARSAT34B Epoch 852136200 - RIPSAT13A Epoch 1154425920

Posts: 270
Joined: Fri Feb 23, 2007 9:33 pm
Location: Ipswich, Suffolk.

Post by Hawk »

I think you're supposed to count a number of stars in a given constellation. i.e. How many stars can you see in the constellation of Orion, or how many stars can you count in the square of Pegasus? This will give you a better guide to the levels of light pollution in your area. :wink:
Hawk (yes, that's my real 1st name)
Skywatcher Explorer 150P
Nikon D2x

RL Astro
Posts: 749
Joined: Tue Jan 24, 2006 6:09 pm
Location: Plymouth

Post by RL Astro »

I've heard of counting stars in the Square of Pegasus before but I think your eyesight plays a large role in it as well as light pollution. You might just be able to see 5 stars in the Square but someone standing next to you might see 30 odd.
Also counting the stars in your whole sky might be a bit tricky if you can see the band of the Milky Way :wink:

Posts: 15
Joined: Thu Aug 09, 2007 9:34 pm
Location: Northern Scotland

Post by S2 »

The "Great World Wide Star Count" has a couple of examples of how to do this, for Cygnus in the NH and "the Teapot" in the SH.

Sorry to say this, but 98 doesn't really sound a lot. :(

Posts: 3
Joined: Thu Nov 29, 2007 11:34 pm
Location: Rotherham

Post by nibor »

Hi dream_mas.
Take a look at this site
You may find the answer to your question here!

carlos dfc
Posts: 371
Joined: Wed Sep 20, 2006 2:34 am
Location: Nr. Darlington - UK

Post by carlos dfc »

Another way is to scrutinise a star chart, to see what is the dimmest star you can see, within a given constellation.

I use Ursa Minor when it is 'above' the Pole - and Cassiopeia when Ursa minor is below thw Pole.
(You'll always see more stars high above you, than when a constellation is low in the sky.
Dimmest star you can still see, gives a good estimation of you NELM (unaided-eye-limiting-magnitude)

I get about 4.2 - 4.5 from my back garden :cry:
C8 'classic' SCT - 150mm newt - 90mm Mak (grab'n'go) - 10" ATM Dob (W.I.P.)
54.6 N - 1.6 W

Post Reply