Additional Comments
Quote:
Originally Posted by glenc
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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!
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