Extremely dark skies

[andrewk_82 (Andrew)]

I was just looking at this article http://www.skyandtelescope.com/resou...tml?page=1&c=y at was wondering if anybody on this forum has experienced a class 1 dark sky as described in this article (limiting magnitude 7.6 - 8) . Even class 2 and 3 seem extremely good.

To me it sounds a bit like astronomical heaven and not like anything I've ever heard described before. If skys really get that dark I want to know where!!!

Cheers

[Ian Robinson]

Yes - but I had no telescope with me as I was on 4x4 holiday in the Kimberleys and again a remote place in deserts areas of NT.

So how many visual stars (no telescope) can you count in the Plieades ?.... that's my measuring rod.

Best I can manage from my backyard is 10-12, under good skies 14-16.

Limit mag 7.5 would give 21.
Limit mag 7.8 would give 25.
Limit mag 6.5 would give 12.

See Guide V8 1degree centred on Pleiades.

[Blue Skies (Jacquie)]

Yes, I've experienced a night with a limiting mag of 7.6 I've never forgotten it. It was April/May and around 3am the Sagittarius region of the Milky Way was directly overhead. The dust lanes were black, compared to the background glow of the sky away from the star clouds and it looked like I could just reach up and pull the Milky Way apart to see what was beyond... Don't see nights like to often.

[ausastronomer (John Bambury)]

Hi Andrew,

I have experienced Bortle Class 2 skies on several occasions and they may well have been Bortle class 1. The most recent was in October 2007 at Coonabrabran when we experienced excellent conditions. I obtained regular repeatable readings of between 21.85 and 21.9 on my Unihedron Sky Quality Meter. M33 was visible naked eye. Keep in mind that when John Bortle talks about observing M33 with direct vision, he is in the Northern hemisphere observing it at the zenith. We are observing it at about 20 degrees elevation only and looking through a lot of murk down there. I have also experienced excellent skies on the West Coast of New Zealands South Island in the unpopulated areas up around Franz Joseph Glacier and down South near Doubtfull Sound. The only problem over there is you only get one clear night a month; and thats in a good month!

Cheers,
John B

[astronut (John)]

I experienced a sky between 1 & 2 last year at our Dark Sky site south of Berrima in N.S.W.
At 60 degrees above the Horizon, The Helix Nebula (Mag 7.1) was visible as a naked eye object, not nearly or maybe, Blind Freddie could have seen it.

[andrewk_82 (Andrew)]

Originally Posted by astronut

I experienced a sky between 1 & 2 last year at our Dark Sky site south of Berrima in N.S.W.
At 60 degrees above the Horizon, The Helix Nebula (Mag 7.1) was visible as a naked eye object, not nearly or maybe, Blind Freddie could have seen it.

There is hope for me yet then. I'm going camping next Thursday at a site about 450 kms from Brisbane and about 25kms from the nearest town that has a population of about 900 people. The closest large town is about 80kms away with a population of 12,000. I've been camping there quite a few times but not since I've been interested in astronomy, so I didn't really take much notice of the sky at night.

Helix Nebula naked eye, that would be awesome.

[Omaroo (Chris Malikoff)]

Originally Posted by astronut

I experienced a sky between 1 & 2 last year at our Dark Sky site south of Berrima in N.S.W.
At 60 degrees above the Horizon, The Helix Nebula (Mag 7.1) was visible as a naked eye object, not nearly or maybe, Blind Freddie could have seen it.

I was there that night. I remember John and I turning to each other, pointing, and saying "Nah...can't be".

[astronut (John)]

I'm hopeful for the same sort of sky this weekend at the same site!!
I'm after "The Horsie" and Pease 1, a Planetary in M15 GC.
There are many other faint fuzzies that are on my list!!
Bring on the dark sky.

[Mombat]

I remember back home i used to get what i would think of as class 2 and possibly class 1.
Where abouts where you in relation to berrima were you Astronut and Omaroo? I used to live in canyonleigh which is west of berrima on the other side of the Highway. Our property is about a 30 minute drive out from Moss Vale which would be the nearest town. It was all bush so the only clear area was about 2 acres we had cleared leaving the bottom 10- 20 degrees of the sky hidden.

[Omaroo (Chris Malikoff)]

Originally Posted by Mombat

I remember back home i used to get what i would think of as class 2 and possibly class 1.
Where abouts where you in relation to berrima were you Astronut and Omaroo? I used to live in canyonleigh which is west of berrima on the other side of the Highway. Our property is about a 30 minute drive out from Moss Vale which would be the nearest town. It was all bush so the only clear area was about 2 acres we had cleared leaving the bottom 10- 20 degrees of the sky hidden.

Mombat - Canyonleigh is about 10km from where our forest site is and on the same side of the Hume:

http://www.macastro.org.au/home/inde...d=56&Itemid=83

[Mombat]

Belanglo state forest i used to live i.e. when i was 1 or two in the house on the hill as you drive into the forest. The house with the really high pitched roof on the hill. From our house we can drive though the fire trails into belanglo.

Good skies there i still have to take my scope back home to take advantage of them all i got to use was an el cheapo 60mm refractor. But they are still some of the best views i have ever seen.

[gary]

Originally Posted by andrewk_82

I was just looking at this article http://www.skyandtelescope.com/resou...tml?page=1&c=y at was wondering if anybody on this forum has experienced a class 1 dark sky as described in this article (limiting magnitude 7.6 - 8) . Even class 2 and 3 seem extremely good.

To me it sounds a bit like astronomical heaven and not like anything I've ever heard described before. If skys really get that dark I want to know where!!!

Cheers

Hi Andrew,

As I have discussed on this forum before, Australia is pretty much one big
observing field. You have probably seen the satellite imagery showing the
globe at night. As it turns out, once you get away from the light pollution
'footprint' from towns and cities in Australia, it is pretty uniformly dark.
This is opposite to continents such as North America and Europe where it
is extremely difficult to find anywhere dark at all.

So in the end, it doesn't matter much whether you are in Lake Mungo, or
the Flinders Ranges, the Kimberley or the McDonnell Ranges or somewhere
on the road between Windorah and Birdsville, it is pretty much the same
when it comes to how dark it is, simply because the mean distance to the
nearest outdoor light bulb is a long way away.

In fact, what tends to differentiate one dark sky site from another in Australia
I find comes down to other attributes, such as the seeing and transparency
and general amenity and climate of the observing location.

For example, I would rather observe from the top of Mt. Kaputar, which is
a hop skip and a jump away from Narrabri, rather than observe from, say,
the West Macdonnell Ranges. The reason, you are at 1350m above sea
level on Mt. Kaputar and unlike the Macdonnell ranges or the Gibb River
Road in the Kimberley, you don't have two thousand flies crawling around your
eyes and corners of your mouth at 8pm as they try and steal every last
microgram of moisture they can find.

So you do indeed live in the lucky country. The types of dark skies that
those in other parts of the world can only ever read or dream about are
often less than a half day drive away from any major Australian city.

Pack the scope and get out and do it some time if you get the chance.

[andrewk_82 (Andrew)]

Originally Posted by gary

For example, I would rather observe from the top of Mt. Kaputar, which is
a hop skip and a jump away from Narrabri, rather than observe from, say,
the West Macdonnell Ranges. The reason, you are at 1350m above sea
level on Mt. Kaputar and unlike the Macdonnell ranges or the Gibb River
Road in the Kimberley, you don't have two thousand flies crawling around your
eyes and corners of your mouth at 8pm as they try and steal every last
microgram of moisture they can find.

So you do indeed live in the lucky country. The types of dark skies that
those in other parts of the world can only ever read or dream about are
often less than a half day drive away from any major Australian city.

Pack the scope and get out and do it some time if you get the chance.

Thanks Gary,

I had a look and Mt Kaputar is less than a 3 hr drive from my place. I'll have to go there for a camping trip next chance I get. I'm surprised that such a good sight is so close to home. I thought I'd have to go to the middle of nowhere to get the skies described in that article.

Cheers

[Paddy (Patrick)]

The best skies I have ever seen were long before my astronomical obsession, in the countryside of Tibet. I had and have never seen stars so bright and striking. I had seen plenty of very dark skies before over years of offshore sailing, but these dark mountainous skies were something else again!

[mickkk]

King Island. About 9 houses and 50 people on the joint, 2 streetlights.

Well its not quite that backward, but it has the clearest skies Ive ever seen. Lying on your back and looking at the milky way is amazing. Was staring south once and saw about 2 shooting stars a minute.

The locals said that was pretty normal for there.

Theres not a lot to do at night, so if you like star gazing, head there!

[ngcles]

Hi John & All,

John wrote:

"The most recent was in October 2007 at Coonabrabran when we experienced excellent conditions. I obtained regular repeatable readings of between 21.85 and 21.9 on my Unihedron Sky Quality Meter."

As a matter of interest, I was up at Mudgee (Gratti) for the last several days (only got one good night).

On that night (Sat 29112008) at 11.30pm I got readings on my SQM/L (my method is to take four readings, discard the first and average the following three) of 21.88, 21.90 & 21.90 making an average of 21.89. On this reading run it beeped between 12 and 13 times before readout (lots of beeps means lots of dark).

The "worst" averaged reading I got for the night was 21.84. The best single reading (not a first reading) was 21.91.

This equates to a ZLM of about 6.6. M33 was just visible naked eye. The Milky Way was incredibly detailed, marbled and dozens of O.Cs visible naked eye. At one stage I counted 14 stars in the area bounded by Betelgeuse, Bellatrix and the belt stars of Orion. It was a very, very good night -- I spent half of it gawking (slack-jawed and dribbling) naked-eye. I'd say it was a Bortle 1-2.

I love my SQM if only because it is totally objective provided it is used in accordance with the manufacturers instructions and people don't "gild the lily".

Best,

Les D

[gary]

Originally Posted by ngcles

The Milky Way was incredibly detailed, marbled and dozens of O.Cs visible naked eye ...

I love my SQM if only because it is totally objective provided it is used in accordance with the manufacturers instructions and people don't "gild the lily".

Hi Les,

Thanks for the post and sounds like you had a good night out.

One thing you do have to look out for is, as per the manufacturer's web site, that
these devices make no allowance for the Milky Way. Your "L" model has
a lens that restricts the FOV to around 10 degrees, which as you know is
still quite wide with our Milky Way infested skies at these latitudes.

One of the first things that strikes southern hemisphere observers when first arriving
at latitudes under northern hemisphere skies, is "where are all the stars?".

With the Milky Way often at the zenith here, when arriving at night at a place free of
all artificial light pollution and the glow of the Moon, often the first thing that strikes
you is that there is sufficient light from the Milky Way to set up the scope with
minimal or no requirement for a flashlight!

I suspect that an apples to apples comparison is often not going on when comparing
readings from these devices from locations in North America to locations in
Australia simply because of the Milky Way surface brightness.

We are indeed comparatively lucky down here.

Best regards

Gary

[ausastronomer (John Bambury)]

Originally Posted by gary

Hi Les,

With the Milky Way often at the zenith here, I suspect that an apples to apples comparison is often not going on when comparing readings from these devices from locations in North America to locations in Australia simply because of the Milky Way surface brightness.

Best regards

Gary

Hi Gary,

I have no doubt you are 100% correct with this assumption. I have had nights of outstanding observing conditions and still only obtained readings in the 21.5 to 21.7 range because of the Milky Way brightness. The sky quality on those nights correlated to higher readings than what could be obtained on the SQM. As you are probably aware my SQM is the older model which is more affected by Milky Way Glow than Les's newer model. You were at Coona the night I got those repeatable readings in the 21.85 to 21.9 range and you would have to agree they were outstanding observing conditions, which you don't encounter all that often.

Cheers,
John B

[ngcles]

Hi Gary, John & All,

Yep we certainly do live in one of the best locations in the world to be an amateur observer and for a great many of us, only a couple of hrs drive is needed to reach an excellent or even pristine sky.

I remember the one night I observed with Steve Gottlieb from the U.S at my "nearly dark" site in the Southern Highlands not far from Bargo, he was blown away by how good it was just over an hour from the centre of Sydney. He felt it the equal of many sites they boast about in California, yet I've got the "hide" to label it "nearly dark".

Re the SQM readings from overseas, see:

http://www.unihedron.com/projects/da...tatistics=true

There are several readings in the high 22s and even up to mid 23s that I am a little suspicious of ...

I wonder if these people were standing in the shade of a tree or maybe have fudged things ... just a wee bit ?

The night up at Mudgee last weekend (only 1 clear night) was up there with the best few I've seen from there. Haven't observed from Kaputar yet -- one day, it sounds a wonderful spot!

Best,

Les D

[bmitchell82 (Brendan)]

I used to live out on stations in the NT, one was 2.5hrs drive from darwin... and darwin on the LP map was only a speck. The memories of laying on the back of the tray of the truck looking up was phenomenal... too bad i didn't have my astronomy obsession then. I can agree with you that the milky way lights the place up. ahhh camping trips.