That combination Cloud and Light Pollution map is a ripper, but I don't get the two areas with massive light pollution in the oceans (see 2 red circled areas in pic below).
They can't be oil rigs as they are the size and brightness of large cities!!!!!!!
Ken,
The one off Karratha (WA) is almost certainly gas production, and the one off E Vic might also be gas - there is gas production in E Gippsland, but whether it is related I'm not sure...
Take a look at the LP map for W Europe at the website, and you will see that it looks like the North Sea is full of 'brightness of large cities' - all oil rigs. Same across the Persian Gulf and SE Nigeria - almost the only lit-up place in Africa.
Now let's pray there is nothing of value to be dug up in Coonabarabran - or in Snake Valley, for that matter....
I have 30 arc second topo that I could use as the background, but to be honest it isn't going to prove much - the BOM doesn't, generally speaking, stick their climate stations on the tops of mountains. They are mostly in the middle of populated areas, so we lack real data for the hills.
For those who are curious, that spot with 169.8 clear days on the central coast of NSW is Harrington, 31.87 °S 152.68 °E, on the coast near Taree.
I've also included the data for Coonabarabran, for those interested.
Whilst I don't doubt the accuaracy of these figures for low areas, I can add the following in regard to the "higher level areas".
Steven Lee and other staff who work at the AAT, keep a very detailed record of all the relevant weather conditions each and every night at the AAT at Siding Springs, as part of their observational logs and respective telescope usage. I was chatting with Steven in October about the number of clear nights at Coona. He indicated that each year they averaged just over "200" clear observing nights, on top of the mountain.
Cheers,
John B
Last edited by ausastronomer; 24-01-2008 at 06:49 AM.
Interesting thread. Much of the site testing in Australia were made after the WWII. Some of this information remains in the National Library in Canberra.
Some papers exist on the subject, especially on the number of clear nights and seeing. After these works, Australia was considered a generally poor observing place - mainly as the mountains here were not high enough to place telescopes. Sadly the desert sites, although dark, is deem unsuitable due to distances to get there and the gross temperature extremes - especially in summer.
1) Interested readers here should download the probably definitive ADS pdf article written in 1960 by Bart Bok on this very subject, including a few maps. Ie. http://adsabs.harvard.edu/abs/1960JRASC..54..257B
4) Also interesting in Russell Cannon's "Some comments on large telescope astronomy in Britain and Australia.", which discusses placing very larger telescope in Australia and Britain. There are some comments on the general site conditions in Australia.
Ie. http://adsabs.harvard.edu/abs/1989Ap%26SS.160..275C
================
It should be possible to do your own site test, which could probably be made using daily satellite information from the weather bureau of the cloud cover at one site or another. Cloud cover, measured by either Campbell-Stokes sunshine recorders (a glass sphere burning marks on a card.) or so-called specially made gas-phase nephelometers - the latter used to measure daylight transparency (technically called; "atmospheric albedo") and distant visibility to the horizon. I read once about how one could be made, which I think was in Amateur Scientist in an old Scientific American.
Although these are important professional papers, there are many clues about general site selection. These sources are fairly uncomplicated reading.
Here is Eric's 'Clear Days' map, again superimposed on the light pollution map. All colours have been converted to scales of gray in order to improve readability, so now the darkest spots are the best to observe from a 'clear day' and darkness perspective - atmospheric conditions are not accounted for, and the limitations Eric noted apply here too.
Still crude and unscientific, but it does give a rough idea...perhaps time to start contemplating The Great Tibooburra Star Party....
Interested readers here should download the probably definitive ADS pdf article written in 1960 by Bart Bok on this very subject, including a few maps. Ie. http://adsabs.harvard.edu/abs/1960JRASC..54..257B
Thanks for all that, it was interesting to read through. I wonder what good dark sky sites were excluded at the time due to remoteness, which today might be looked upon more favourably?
One more graphic, to make it easier for those who like to overlay additional data. This one was done using interpolation of the climate station data to create a 3 arc minute grid, allowing a higher level of detail to show through in the areas in which it was available.
...it was interesting to read through. I wonder what good dark sky sites were excluded at the time due to remoteness, which today might be looked upon more favourably?
I think at the time there were a number of places that we set aside - Maralinga is one that come to mind - where the British decided to do some atomic bomb tests. Also Woomera region was rejected because of the security defence area This was probably why the observing sites like in the Flinders Ranges were never finally considered.
Another significant problem with desert regions was/is dust, with significant maintenance cost of clean mirrors and mechanical parts of the mount.
Yet the big issue remains altitude to get as less atmosphere as possible between the telescope and size.
Places like Kata Tjuta and Uluru, would be great places for large observatories - but the Aboriginal people I think might object a wee bit if we did that.
If it were me, I'd place an observatory somewhere on the ancient West Australian-Northern Territory plateau, several hundred kilometres either north or west of these places, and construct either a remote observatory - serviced every month or two. It is the right latitude, and still dark enough from any main city.
If I was made the "Australian Minister for Astronomy" and was going to select my ideal site, it would be on the north-western edge of the Nullabour in Western Australia, where the flat plain rises into the plateau. This would be abut 400 km east of Kalgoorlie and 300 kilometres from the Great Australian Bight , and roughly 80km north-west of a place called Rawlinna. The area is near an ancient inland river that once moved from north to south and flowed into the shallow sea that is now the Nullaboor [plain]. While remote, it would be the darkest of sites in all of Australia and would remain so for ages. (See attached map)
While this fantasy won't happen, you could at least be far from the maddening crowd!
OK, below is the last instalment: Eric's 3' grid map and the light pollution map superimposed. Still crude, but a bit less unscientific.
The two faint red lines contain the 25°-35° latitude belt identified in Bart Bok's paper (indeed, interesting reading!), and the red dot E of Kalgoorlie is the spot Andrew mentions in his post below - the nearest station happens to be called 'Seemore Downs', so someone out there agrees with him...
Thanks for all that, it was interesting to read through. I wonder what good dark sky sites were excluded at the time due to remoteness, which today might be looked upon more favourably?
Between a rock and a hard place... 'looked upon more favourably' would likely include road or air access, and inasmuch as this is available in remote locations it primarily serves the mining industry... i.e. many inland roads lead to badly light polluted areas...
Some Bureau of Meteorology Places With Reasonable Clear Skies, In Summer, In Order Are:
1. EAST of longitude 141 degrees which is the NSW & Vic border.
Mildura Post Office
Tibooburra Post Office
Condobolin Retirement Village
Albury Pumping Station
Bourke Post Office
2. CENTRAL (long 129 to 141) western Qld, NT, SA
Marree (Farina)
Leigh Creek Aero
Birdsville Police Station
Moomba
Finke Post Office
3. WEST of longitude 129 degrees which is the WA border.
Denham
Hamelin Pool
Barrow Island
Medina Research Centre
Paynes Find
Some Bureau of Meteorology Places With Reasonable Clear Skies, In Autumn, In Order Are:
1. East Of Longitude 141 Degrees Which Is The NSW & Vic Border.
Julia Creek Post Office
Tibooburra Post Office
Longreach Post Office
Croydon Township Qld
Charleville Post Office
2. Central (Long 129 To 141) Western Qld, NT, SA
Cloncurry Airport
Tennant Creek Post Office
Moomba
Birdsville Police Station
Wave Hill
3. WA
Bidyadanga
Port Hedland Post Office
Cockatoo Island
Koolan Island
Broome Post Office
Some Bureau of Meteorology Places With Reasonable Clear Skies, In Winter, In Order Are:
1. East Of Longitude 141 Degrees: Qld, NSW & Vic.
Croydon Township Qld
Julia Creek Post Office Qld
Georgetown Post Office Qld
Normanton Post Office Qld
Richmond Post Office Qld
2. Central (Longitude 129E To 141E) NW of Qld, NT & SA
Wooliana
Cloncurry Airport
Newcastle Waters Post Office
Wave Hill
Kidman Springs
3. WA
Mount Elizabeth
Cockatoo Island
Wyndham
Bidyadanga
Koolan Island
Some Bureau of Meteorology Places With Reasonable Clear Skies, In Spring, In Order Are:
1. East Of Longitude 141 Degrees: Qld, NSW & Vic.
Croydon Township Qld
Georgetown Post Office Qld
Julia Creek Post Office Qld
Richmond Post Office Qld
Longreach Post Office Qld
2. Central (Longitude 129E To 141E) NW of Qld, NT & SA
Cloncurry Airport Qld
Mount Isa Post Office Qld
Tennant Creek Post Office NT
Borroloola NT
Ngukurr NT
3. WA
Mandora
Cockatoo Island
Bidyadanga
Mardie
Broome Post Office
Happy Australia Day to My Fellow Australians!
May Our Spirit Under the Southern Cross Never Set On Our Shores!!
Aussie, Aussie, Aussie. Oi! Oi!, Oi!
Glenn
Just some general comments. One of the biggest problems with weather forecasting, is that the majority of the predictions are tailored for daylight. While it is true that these trends follow an almost predictable phenomena, the problem with night time observations is that what is interesting to all astronomers seldom have any real data. An example is cloud cover, where most devices measuring the % cloud are not made at night. This is also true of atmospheric transparency and visibility of the horizon. I remember hearing a fellow from the BOM who said there was little correlation to conditions at night to the day.
Moreover, sometimes this is annoyingly true. I cannot count the times when we have had a brilliant blue sky day, being clear from horizon to horizon. After dusk becomes either covered with high cloud or becomes overcast all night, only to dramatically clear after the sun has risen. The opposite is also sometimes true.
An example is for Canberra, whose average number of clear days according the BOM site in the last 80 years was averaging 100.0 days, and yet Bart Bok says in his paper says they had the average of 196 nights in 1959 where the 74-inch at Mt Stromlo was operable - almost double the BOM's data. (if the data range is reduced to between 1941 and 1970, roughly in the time frame of Bok's paper this was a slightly worse 98.2 days.) While these figures aren't probably truly statistically equivalent for the site, differences of a factor of about two is certainly significant.
In all, I think we have to be very careful when adjudging dark sky sites, and these should be really be tested visually as much as possible. I think this is the reason site testing is so important.
Note: I know of one astronomical group in Australia who purchased a site, which is located in an unsuitable location with cloudy cover that is higher than the surrounding districts. Often cloud condenses at night with the drop in temperatures over the top of the mountain itself - and stay there all night - only to clear again when the temperature and the morning winds come in. Yet, in most of the districts around it will remain perfectly clear. When it is clear, sometimes the sky is truly brilliant, but some of the time the seeing is dreadful due to turbulence cause by winds having to rise over the higher mountainous regions. Right or wrong, such problems are clearly very complicated, and it takes really years to understand the local climatic conditions. Had they read Isadore Epstein's paper of 1959, they would have not selected a now rather less than ideal site.
This is why it is best to get the feel of the site before building anything - mainly because of the expense. The ASNSWI, for example, did this at Bowen Mt., and ended up with a valuable observing site that is pretty good most of the year.
Site testing has been conducted thought the world in the last 60 years or so. Perhaps the best example is the now defunct observatory site at Black Birch on the mountains of the northern South Island near Blemhelm. Here an observatory was constructed, which was site test by the A. Bateson and the recently late Roger North, who stayed in nothing better than a wooden shack on the mountain for a year or so. So valuable was the data, that it produced the Black Birch observatory under National NZ Carter Observatory in Wellington. This same information then prompted the US Naval Observatory to set up a transit telescope doing southern star positions in the late-1980's and 90's.
Whilst amateur astronomers perhaps do not need such sophistication, it shows a valuable lesson in understanding local weather conditions - sure using meteorological data is important - but it sure does not beat visual observations.
Unfortunately, most of us do not choose a site based on the conditions at night, because a residence is usually selected because of the geographical position of work, family and lifestyle; and not for ones own hobby. Those who have jobs in the Country, certainly have some advantage finding a suitable deep-sky site that is not too far away - perhaps travelling less than 10 km out of town, City dwellers, like me in Sydney for example, have to travel >80 kms to some deep-sky site where their is no guarantee of a decent sky when they get there.
Finally, as to my selected site in WA, this is placed near Sites 18 and 19, which is Kalgoorlie, and just west of Kalgoorlie. Rawlinna is the main rail line that goes between Adelaide and Perth, and was set up in 1919. The data between these two places is interesting - more so in that the kind of weather experienced between Siding Spring at Coonabarabran and the site I refer too are in some ways remarkably similar. What I should have mentioned is this region is one the edge of the Great Victorian Desert, on the very fringes of possible agricultural production. Any further west from here, passing into South Australia is such a hostile environment, that the maintaining astronomical work would be both expensive and difficult.
(See Australian Deserts on the wiki image at; http://en.wikipedia.org/wiki/Image:A...ia_deserts.PNG )
This also wiki image shows the geography of the region I have referred, where the low flat region Nullarbour extends.
As for nearby facilities, as alluded too by Karllson, if a large telescope were ever built here, it has the advantage of the nearby railway line, and transportation of the telescope equipment. Kalgoorlie and Rawlinna both also have airports.
I think in all there are only three regions to choose from, south-east WA, the Flinders Ranges, and mid northern NSW - roughly on a direct line between Perth and Sydney. The regions in between are just unsuitable both climatically and observationally.
As to the earlier comment on gold fields in this region, most are now already underground, with the aluviate fan and ancient delta of the region, being already being mined on the ground for its wealth. I think much of the mining is conducted north and south of Kalgoorlie so light pollution shouldn't be a problem at all.
The bottom line is that it would be more cost affective to move new optical observational facilities to South America high in the Andes. Our Federal politicians, seemingly made by Johnny Howard of course rejected contributing costs to a new large telescope under the ESO in South America.
With the U.N. Year of Astronomy in 2009, this would have been a great opportunity for Australia to shine on the world stage, so our glorious astronomical history becomes slightly more diminished. Pity.
Cheers to all,
Andrew
Note: Not wanting to stop on a downer (and I don't mean Alexander)... Again.
Happy Australia Day to My Fellow Australians!
May Our Spirit Under the Southern Cross Never Set On Our Shores!!
Aussie, Aussie, Aussie. Oi! Oi!, Oi!
Some BOM Places With Reasonable Clear Daytime Skies, For The Whole Year, In Order Are:
1. East Of Longitude 141 Degrees: Qld, NSW & Vic.
Longreach Qld Julia Creek Qld (places in bold are in 4 of these lists)
Tibooburra NSW Croydon Qld
Charleville Qld
Bourke NSW
2. Central (Longitude 129E To 141E) NW of Qld, NT & SA Cloncurry Qld
Tennant Creek NT
Birdsville Qld
Jervois NT
Boulia Qld
Mount Isa Qld
3. WA (The best 5 places are in WA, followed by Cloncurry)
Port Hedland
Barrow Island north of Onslow
Onslow Bidyadanga, south of Broome
Mardie, north of Onslow
Mandora, north of Port Headland
The "map" shows the 5 best places in Oz for blue skies.
Local people might be able to do some site testing near the above places. http://www.bom.gov.au/climate/averages/
The "map" shows the 5 best places in Oz for blue skies.
Local people might be able to do some site testing near the above places. http://www.bom.gov.au/climate/averages/
Forget anything between Dampier and Port Hedland... blue skies perhaps, yes, but also heavy light pollution from the NW Shelf gas operations centered around Karratha and the iron ore industry across the Pilbara centered around Port Hedland. I say that not just because the map shows it - more than once I have seen it with my own eyes...
Selecting Astronomical Observing Sites
best stay away world 
shhhhhhh
