How dark are your skies ?

[slice of heaven]

2 part question

Given you had near perfect seeing and transparency , what magnitude can you see down too with your naked eye from the sites you observe from ?
I know on average I can see down to mag 5 from the backyard, only wishful thinking gets me past this.

What is the accepted method currently of determining the magnitude of stars?
I know it was originally scaled that mag 6 was the limit of stars viewable by the naked eye, yet I've seen people quote they've viewed from mag 7 or better skies?

[ballaratdragons (Ken)]

Slick,

how can I tell? I haven't got a Mag meter! How do you know what Mag a star is.

Yep, 20 years at this and I still know nothing

[slice of heaven]

BD

Maybe someone can make us one?

I'm just going by the mags printed on star charts when viewing, I start with the stars with a mag I can pick up by eye to align the Telrad,then use the scope to zone in closer.

[ballaratdragons (Ken)]

Oh!

I suppose it depends on the viewers eyes too.

I suffer from a condition called 'Night Blindness' which means I can't see in near dark!
I do not seem to be affected by it through the scope though, as objects are brighter hence I can see them easily.

Aboriginal children have the best eyesight and night vision of any people on Earth. They have been recorded at reading car number plates clearly at over 0.5 k away!!! and can draw the night sky including stars we can only see with knockies! That amazed the specialists.

Fred Hollows mentioned it a couple of times too, and it puzzled him how Aboriginal eyesight deteriated so fast after puberty. (not from disease)

[slice of heaven]

Yeah, I wish I had my kids eyes.Must be the tunnel vision they have. My 4 year old has eagle eyes, she's the first to spot a star or planet as the sun goes down and can pin point a plane while it's just a dot,I've learnt not to doubt what she says she sees.

[ballaratdragons (Ken)]

Haha! Aaron (Harry) said he could see Jupiter in the afternoon daylight about 3-4 months ago. I told him he must be mistaken but he was adamant! I got the knockies out to show him he is seeing things and . . . there it was! Hmmppphhhh!

[cventer]

if you want to measure it very accurately you can get a SKy Quality Meter from Unihedron www.unihedron.com


I have one and its very cool to measure sky darkness at different locations. Only problem is the old timers hate you becuase next tme they give you the ole "site x is the darkets I have ever seen etc... you now have something to measure their statement by.......

Best regards
Chris Venter

[slice of heaven]

Cool tool Chris

[dhumpie]

One way to establish your limiting magnitude is to go and get the latest edition of StarWare by Phil Harrington. He has a map of the southern cross and from memory they go down to mag 6 or something. Using that map I determined my suburban sky to have a mag limit of between 5.4 (summer) and 5.6 (highly transparent winter nights). Good enough to bag mag 10 and brighter galaxies

Hope that helps.

Darren

[Striker (Tony)]

Intersting Post...I dont know what mag I can see...the next clear night I will have a look to see what magnitude star I can see....

[asimov (John)]

The accepted method awhile back was to if you could see any stars with the naked eye in the coal-sack. If you can it's mag 6 & better.

[ving (David)]

have to check... brb!









ok, cant see any stars at all!!!
(cept sol)

[asimov (John)]

Heres a few links: http://www.go.ednet.ns.ca/~larry/astro/maglimit.html

http://www.go.ednet.ns.ca/~larry/astro/maglimit.html

[rmcpb (Rob)]

Not really about the dimmest star you can see but this site gives a way of measuring the magnitude of the whole sky from a site:

http://www.saguaroastro.org/content/...gMagnitude.htm

Its a bit of fun to brag about your really, really, really dark sky

Cheers

[gaa_ian (Ian)]

I like those charts Rob

[Mick (Michael)]

Here's a link that maybe of interest. How many stars

[slice of heaven]

Ya Wally Ving, were all at mag -26 sites when the suns out
Heres a link for a more simplistic assessment

http://cfa-www.harvard.edu/icq/MagScale.html
The astronomical magnitude scale.

Might have to recheck mine if the moons of Jupiter are visible at mag5.

That chart goes down to mag 7 for naked eye limits, below the original mag6 limit of the original charts. Have the skies become darker in the last 2000 years, or who changed it?

[fringe_dweller]

Due to doing a lot of meteor obs reports i got to know how to tell at a glance without even looking for specific stars roughly what the LM at Zenith is at my familiar sites - ie backyard ect. Slice i am surprised that you only see down to mag 5 at MB! In my backyard in suburbia near ttg plaza I can see down to nearly mag 6 in certain darker areas of my overall sky in the east and S/E - but in the north and west it is very bad - rarely more than 4.5 - 5. At our dark site near Mt Pleasant i have noted stars down to 7.2 at zenith (with effort) at times. Depends if you are talking about wether you can see them easily or with effort see them come in and out of view. I find the visual appearances of the Magellenic clouds to be great rough guide to conditions for us in the s.hemis.
I used to use this site http://www.namnmeteors.org/lm_calc.html for meteor obs before I started printing out charts with snp to the mag i wanted and in the fields i wanted (I re-use them over and over forever now) - and then marking/numbering stars at various relevant mags and writing them down on a seperate page for reference.
Also the bortle scale is a great scale - wish it was more popular - I have read people can see down to mag 8 at extreme sites on top of 5000 mtr chilean mountains ect. in perfect conditions :-) wish there was a southern hemisphere specific version of the bortle scale.
http://www.frostydrew.org/observator...ays/bortle.htm
Kearn

[slice of heaven]

My assessment was only on an average its mag5 across the sky Kearn. When starhopping I will use mag5 or brighter in the Telrad so I'm only taking into account the stars I dont need to struggle to see.
All the factors you've listed come into play in how to actually calculate a sites darkness, and with so many variables it seems hard to actually determine how dark a site truly is.
Does 1 mag6 star at zenith thats barely recognizable make it a mag6 site?
There doesnt seem to be a true definitive measure of a sites darkness, unless of course you have Chris' cool tool.

[fringe_dweller]

Originally Posted by slice of heaven

Does 1 mag6 star at zenith thats barely recognizable make it a mag6 site?
.

technically, yes mate - if you are making a conventional report and that is the accepted criteria for the format, then yes than it is a mag 6 sky.
Kearn