What is a dark site ?

[SilverAstro]

The best way of determining the (NELM) quality of one's site/sky is not to rely on websites (nor gizmos) but to get out there and look up ! :-

Select a constellation that you recognize, see what dim star is in there that you can just see (unaided eye) (just about see or see averted)

Go to Stellarium (others are avai,, oh shut up ! )

and look up its magnitude.

If it is about 3 - sad

If it is about 4 - hope and/or go back to bed

If it is about 5 - brill !

If it is better than 5.5, brag,,,,  yea ! mine outside my front door is >5.5,.,  sometimes, depending upon atmospheric condx !

If you can spot these, unaided, would enable us more to help assess     there are many more charts, online, in similar fashion per constellation)

PS Nice pic !

 

Edited January 22, 2018 by SilverAstro

[Stu]

17 hours ago, JOC said:

That fabulous Stu many thanks - I'd often wondered whether I was poor for light or otherwise.  I have a factory behind me with it's own cluster of lights, but in most places on my land have a hedge between me and those lights.  I am three and a half miles away from the nearest larger town (Which is North) and if I am looking East in particular there is nothing of consequence light wise between my and the open sea.   Looking south-South East I finally hit the large connurbations of Southend and the A127 corridor, but not for about 7 miles in a straight line.  My worse direction seems to be Westerly and although they are a long way away I think it's Chelmsford and to a lesser extent Woodham Ferrers that cause a somewhat yellow glow in the distance in that direction.  I took that shot of Orion (which isn't brilliant I'll be the first to admit) when it was in South-SouthEast at about 45 degrees to the horizontal a couple of nights ago - so def. out in my best direction.  I hadn't considered that it might be useful to take a stab at how dark I am.  I had been really hoping that I did have the fairly decent conditions that I thought I enjoyed so I am really pleased that you've been able to take a stab at this determination for me .  Unfortunately I am not aware that I can really see the Milky Way, but I do sometimes see an awful lot of stars up there.

Sounds like you are a bit better than me. My skies vary between about Mag 4.5 and 5 (on a really excellent night). Using an SQM-L I get between 18.5 and 19.1 (again on a really good night). The best locally is 19.4 which I measured in a local village where we meet to observe, that converts to mag 5.07!

Within about 1.5 hours of here are the South Downs and we measured Mag 21.3 there, which converts to mag 6.2 NELM but that seems a little too optimistic. Regardless, it shows that even within a couple of hours of London there are good skies to be had.

[MarsG76]

Awesome post... a mag 6 sky, now that something to behold... maybe one day.

[Captain Scarlet]

On 4/2/2015 at 09:32, acey said:

A true dark site is not "pitch black"..

This matches my experience of my first properly dark site a couple of years ago in furthest SW Ireland, a couple of miles from Baltimore. Walking back from the pub one evening, I couldn’t actually make out most of the constellations, they were just drowned out in a sea of stars such as I'd never seen before, it was incredible. It was at that exact moment I decided to re-indulge my interest in Astronomy. Having said that, I do recall the only one that WAS obvious was Orion, perhaps that's what was meant by "an Orion sky"  ?

Magnus

Edited January 22, 2018 by Captain Magenta

[VNA]

Similar experience from Glacier Point, Yosemite or the bottom of the Grand Canyon! "Too many stars" Unfortunately from home I can only see Polaris at 1.97 with averted vision--when I moved to my house I could see the milky way in the winter--that was 26 years ago and yet there is no street lights, but plenty of garden lights illuminating trees from underneat and big cities close by.

"Too many stars" or is it "too many notes?" This quote makes me think about a critic of Mozart's music by Leopold the second if I am not mistaken. In any case another critic so fitting is "Music written by an angel and accompanied by celestial harmonies," a critic in a local newspaper of the time! Sorry for distressing!

[Charic]

21 hours ago, SilverAstro said:

.........Select a constellation that you recognize........

I'm not sure it really matters which constellation, on the other hand, Orion for example, is below my horizon except for the Winter season!
However, I have read on several occasions that Ursa Minor is often recommended as your starting point for assessing  your NELM. This link provides some info https://darkskydiary.wordpress.com/2012/01/20/naked-eye-limiting-magnitude-assessing-sky-brightness/

[SilverAstro]

1 hour ago, Charic said:

.........Select a constellation that you recognize........

I'm not sure it really matters which constellation,

You are right, any constellation can be used (pref one that is near the zenith, but that is getting a bit ahead of us in present discussion !)

but my point was "that you recognize", because JOC needs to be familiar with it to be able to pick out a star in the night sky and then be able to identify it in Stellarium, or other star chart, to find its magnitude.

You are also right about Ursa Minor, I use it myself, but I was focused on Orion because that it what JOC has 'got' (aka groked) and is familiar with, at the mo. ! It was not long ago that JOC was unsure which was Polaris, let alone U Min (trouble with an unfortunate tree if I recollect) 

Let us not get whizzing too far over heads, let us focus on birds in the hand, or camera, as the case may be.

 

Edited January 23, 2018 by SilverAstro

[JOC]

8 hours ago, SilverAstro said:

It was not long ago that JOC was unsure which was Polaris, let alone U Min (trouble with an unfortunate tree if I recollect) 

Said tree still gets in the way  That and a bit of light pollution from the factory behind me and I still feel it's not the easiest star in the sky to pick out.  Castor and Pollux I'm usually OK with.  Capella (if I've found those two is a logical progression more of less up above them.  Orion is a real 'belter' (sorry!) though absolutely unmistakable.  The daft thing is the plough I don't have problems with, I can also often find U. minor (baby plough), but even with those two in the bag Polaris still often gets away - even knowing its a double doesn't seem to help!  Therefore @SilverAstro is probably correct to put some instructions on Orion for me - it's a bit more fool proof, and given the fool at this end it probably needs to be ;-)

I am also better with Winter stars than summer ones!

Edited January 23, 2018 by JOC

[SilverAstro]

16 minutes ago, JOC said:

 Castor and Pollux I'm usually OK with.  

Excellent ! Cast around them a bit and get Gemini marked out, it is well placed at the mo. (high up) to enable judging of your NELM with plenty of faint stars to be identified.

Edited January 23, 2018 by SilverAstro

[JOC]

5 minutes ago, SilverAstro said:

get Gemini marked out

I find it's often a bit on its 'side'  with two long trailing 'legs' running from Castor and Pollux - yes? I can usually spot these long lines if nothing else!

[Jonk]

On 22/01/2018 at 08:25, Stu said:

Within about 1.5 hours of here are the South Downs and we measured Mag 21.3 there

Just out of interest, whereabouts?

[Davey-T]

48 minutes ago, Jonk said:

Just out of interest, whereabouts?

I think they named it the Patrick Moore dark sky reserve but don't know where it is exactly.

Dave

[Stu]

51 minutes ago, Jonk said:

Just out of interest, whereabouts?

We observe at a place just south of Bignor on the South Downs way. Quite high and a little exposed but pretty dark

[Jonk]

http://www.darksky.org/idsp/reserves/southdowns/

[Jonk]

1 minute ago, Stu said:

We observe at a place just south of Bignor on the South Downs way. Quite high and a little exposed but pretty dark

The South Downs stretches from Winchester to Brighton so a lot of space to explore! My nearest is Old Winchester Hill, up the road from the Clanfield observatory. If I had an SQM meter I'd measure it on a moonless night. 

I do love it up there and it's only half an hour away.

[Stu]

Just now, Jonk said:

The South Downs stretches from Winchester to Brighton so a lot of space to explore! My nearest is Old Winchester Hill, up the road from the Clanfield observatory. If I had an SQM meter I'd measure it on a moonless night. 

I do love it up there and it's only half an hour away.

Yes, I know.

This place is quote convenient in terms of access whilst being away from passing headlights. Plenty of space to set up too. Sure there are many other good locations across the downs.

[pragmatist]

Fantastic post 

[Charic]

Definitely not a dark site for me tonight, in-fact,  never is during my Summer! especially when the sky is brighter than the street light.
Its just past 2330 Hrs,  looking NNE and its brighter in the West.

 

 

Edited September 27, 2018 by Charic

[Alfian]

In visits to Galloway I've found that the sheer number of naked eye bright stars visible is not only wonderful in a jaw dropping way but initially a little confusing in that that the usual bright stars that I use for finding my way around  are in part  absorbed in the surrounding starlight. Its definitely not a problem to complain about and it sure makes you aware of what probably most of us to varying degrees are missing  most of the time.

[Charic]

Same view as above, but two Months later, and the new street lights (LED) have made a big difference to my plot.
The original large sodium bowl is now a simple spot.
The 'runway' lights are just patio edge decoration, which can be switched off.

 

Edited September 27, 2018 by Charic

[JamesF]

That's an astonishing difference.

James

[Charic]

On 27/09/2018 at 16:16, Alfian said:

.............the usual bright stars that I use for finding my way around  are in part  absorbed in the surrounding starlight. Its definitely not a problem to complain about and it sure makes you aware of what probably most of us to varying degrees are missing  most of the time.

On certain nights here in Scotland, the skies are awash with Starlight ( more-so  away from the houses and street lights ). 

Starlight bright enough to cast body shadows, no that's weird.

Edited October 27, 2018 by Charic

[Charic]

7 minutes ago, JamesF said:

That's an astonishing difference.

James

Huge difference, using same old iPhone.
The Summer up here is just too bright, but now its getting darker, it has to be better this season!
I did not for one moment think I would be applauding the new street lights.

Here's the  left and right view. The left view will be troublesome maybe, once those leaves have dropped, the LED will be more noticeable, and the view to the right is just spoilt by the Trees, covering the Moon. 

 

Edited September 27, 2018 by Charic

[SIDO]

I am a bit stuck in the driveway now and my observing site is what most would consider a dark site but as good as this is years ago I would travel to darker sites which were only slightly darker as sites go and driving around in my car with a trunk load of gear for miles to be out in the stix and afield so to speak made everything seem darker than I think it may have been so back then for me a dark site was a place to go and gamble on the transparency, thermals, bugs, fog and cloud while acting seemingly like I was on holiday and at least knowing that the destination was dark and an awesome start to achieve the game changer needed to succeed a higher level of observation than I could have if I just stayed home and observed from there...but boy what a great and wonderful experience it was and truly some great adventures were logged. Just wanted to get that out there before moving on to answer the question or at least give my answer to it.

I think when one first implies "Dark Site" he or she has concluded that ones current site is not dark enough and a dark site to this individual is any site darker than the current site and at least that much darker so to exceed observations at ones current site making it worth the extra effort and expense not to mention the time. For me there has never been any guarantee the Milky Way would even be visible as transparency varies even at a dark site as does thermal energy transfer, high thin cloud and fog so for me a dark site is just that, a place to go that is darker than my current site, a place where if the variables wind up in my favor the trip is made worthy, a good dark place to throw the dice and hope for the best.

 

 

 

 

 

 

Edited September 28, 2018 by SIDO

[noah4x4]

This week has again justified why I have committed to Hyperstar, camera and EAA in my light polluted back yard in Essex which are necessary to see anything beyond the solar system at my locality. 

I am just about to return to Essex after four nights in the Kieder Forest dark skies site in Norhumberland. It was sunny and reasonably clear most days, but wall to wall cloud after dark. This follows three similar four day trips to the Kelling Heath dark sky site in Norfolk during the last twelve months that were also blighted by similar cloud.

I have to plan such trips weeks ahead and weather forecasting is too imprecise. I reckon I have wasted enough money on fuel and accommodation to have bought a second quality telescope with camera and Hyperstar.  Thankfully, EAA is my salvation. Can't wait to get home; utterly fed up with castles, bleak hillsides and Hadrians Wall; and it is only a 350 mile drive today.....