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Old 26-11-2017, 09:53 PM
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Best latitude for observing ?

I live in northern EU on latitude 52 North. This results in very short summer nights (even with slight astronomical twilight). People in Scandinavia (60 N or higher) even have no nights at all in summer.
In that sense I prefer latitudes around 30-40 degrees or less. with no such extreme differences in summer / winter day length.

And sky coverage descreases when further from the Equator. Therretically, the Poles have only 50%, on 60º N/S it is 75%, on 52 N/S it is 81%, 30 N/S it is 93% and on the equator it is 100%. Considering objects must be at least 15 degrees high, these values are 69% for my latitude and 85% for 30 degrees, 98% for the equator.

And some desert locations have lots of hazy skies, usually in the Middle East and India.

Antarctica would be a nice location, but it is mostly heavily light polluted. Yes you read this correctly. No big cities or other human activities other than small scale scientific stations, but Aurora, which has a detrimental effect on astronomical observations, like you are observing from downtown Los Angeles or Dubai.


For observatories, the equator should be the best place, but the climate in most of the tropics is far more cloudy than around the thirties. Hence, the 39m E-ELT (and other Chilean observatories with scopes ranging till 8m) are between 24 and 30 S, the Keck in Hawaii is on 19 N, and the 10m scope in La Palma is on 29 N and the 10m Salt in Sutherland on 32 S.
Australia has no big telescope (yet ?) despite the climate is favorable for this. Maybe the lack of mountains > 2500m which other contintents / islands do have.

What do you consider as 'the best latitude' apart from the climate or number of clear skies ?
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Old 27-11-2017, 04:01 AM
Christopher-26
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I live in Italy, latitude 39° N. I love the sky how I can see it from here.
But the best latitude is a few degrees upside the Equator. I don't really like Orion overturned like in the southern emisphere...

Seriously, a latitude of 10-15° S IMHO is really good for me.There you can see practically all the sky. You don't lose the interesting areas in Cepheus, Cassiopeia and UMa, but at the same time you can better see southern constellations.

Or, maybe, the best thing is every constellation to zenit, a little impossible.

Last edited by Christopher-26; 27-11-2017 at 04:12 AM.
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Old 27-11-2017, 08:24 AM
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The Mekon (John Briggs)
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If I could choose anywhere in the world to set up a small observatory, to me the best location would be at around 15 degrees south on the altiplano of southern Peru. Nice high location, dark skies - even M81/82 will rise just above the northern horizon. And all the southern sky would be well placed, with the LMC & SMC transiting at around 35 degrees up.
I just wish Australia had such terrain in the northern parts.
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Old 27-11-2017, 12:38 PM
Tropo-Bob (Bob)
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Quote:
Originally Posted by The Mekon View Post
If I could choose anywhere in the world to set up a small observatory, to me the best location would be at around 15 degrees south on the altiplano of southern Peru. Nice high location, dark skies - even M81/82 will rise just above the northern horizon. And all the southern sky would be well placed, with the LMC & SMC transiting at around 35 degrees up.
I just wish Australia had such terrain in the northern parts.
Not wrong!

Its the right latitude here; I have seen ALL the Messier objects from the Cairns region + the sky has a southern bias for great objects (Carina, Omega Centauri, the Magellan Clouds etc) so being situated a little south of the Equator is good.

Ah, but abissal weather conditions here. Last night was the first clear sky that I had seen for almost a month, and the other nights would have been unusable for even looking at the Moon.
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Old 27-11-2017, 01:15 PM
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jenchris (Jennifer)
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I think I'd like to set up Equatorially about 4000 miles up. Geostationary - then I can have day and night astro!!!
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Old 27-11-2017, 02:55 PM
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The challenge is to define “best”. It’s a trade-off between many variables and everyone will rank them differently in importance.

Significant decisions by professionals usually use MultiFunction Attribute Utility Theory or Analytical Hierarchy Process to weight the criteria and score the alternatives, not seat-of-the-pants “I think” type answers. Weighting is usually done with pairwise comparisons and Gaussian elimination.

For the SSO site selection the criteria included political stability of the country, availability of engineering, construction, accommodation, transport and other services needed. Of the optical criteria the percentage of useable observing nights (ie cloud free) was the most important, seeing was a distant second.

FWIW the altitude of Mauna Kea and the ESO in Chile put them above the worst of the cloud.

There are locations in western China (Yunnan), Tibet and Nepal that likewise are technically tropical but their extreme altitude means they are probably quite good locations if you don’t mind the political and social aspects entailed.

Last edited by Wavytone; 28-11-2017 at 09:06 AM.
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Old 27-11-2017, 09:37 PM
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I always thought around 15°S would be best. You get all the southern sky and basically all the best objects the northern sky offers aswell. It also benefits planetary viewing as even when they are at their furthest north they remain at an acceptable elevation.
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Old 27-11-2017, 10:11 PM
glend (Glen)
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As an imager i prefer complete access to the wonders of the southern sky, and believe around 30 degrees south is as far north as i would want to go. I grew up in the northern hemisphere and it just can't compete with the southern sky wonders. Imagers want their target objects to be up high enough to avoid looking through alot of atmosphere, so low angle targets like Andromeda are out anyway.
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Old 28-11-2017, 03:45 AM
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Indeed, about 15 south would be the best. N. Queensland , north of WA, Namibia or far north Chile. It covers the entire sky except opjects north of 65-70N such as the M81/82 or Cat Eye nebula NGC 6543.
I have been in San Pedro de Atacama long ago. Fantastic skies, only a few hundred km from rye 39m E-ELT.
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Old 01-12-2017, 11:46 AM
castor
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The best would probably be around 10-20S. In the Gulf Savannah in Australia there is hardly any light pollution and you are guaranteed clear skies for at least half the year. You can see Cassiopeia/Cepheus and most of the interesting northern objects. M31, M33, SMC, LMC simultaneously visible near culmination is sight to behold in the binocular sky.
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Old 01-12-2017, 12:20 PM
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I live at 30deg S and 1000m altitude. The best for me as it is the most available.
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Old 02-12-2017, 09:05 AM
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I live 12S in Darwin. When a complete newbie about 3years ago, I posted here asking when M31 would be higher in the sky (it was October) and already about 38degrees alt! I now really appreciate what this latitude offers in terms of sky. Even during the wet season, we have a lot of clear nights....and the dry season is mostly cloudless. The downside is LP is catching up in the burbs. And the humidity makes transparency poor for at least half the year. I suspect humidity would be similar across the globe for similar latitudes. Unless you can go up a mountain, and there are no easily accessible areas of altitude elevation here. Oh and I have a theory that goes....the quality of sky for astronomy is inversely proportional to the number of astronomers you will find there. Alas few astrobudies in darwin, so no community.

Clear skies
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Old 02-12-2017, 08:30 PM
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Quote:
Originally Posted by Hemi View Post
And the humidity makes transparency poor for at least half the year. I suspect humidity would be similar across the globe for similar latitudes.
Strange. I have different experiences with poor transparency.
I've been to hot humid tropical climates several times (Bali several times, N Qld once, Tahiti, Fiji, Kenya east cost, KZN which is South Africa tropical east cost), but by far in most cases the sky was crystal clear when there were no clouds.
On the other hand, dry areas like N India and Dubai have an almost constant hazy sky due to blown up desert dust. When landing in Dubai, I see the brownish layer of dust as a blanket over the city.

In E China (and here in the EU as well with eastern winds) haze is caused by particulate matter pollution from mostly car traffic and coal fired power stations.

Water vapor is invisible, unless there are particles in the air which promote condensation. Even here in N Europe I have experience crystal clear nights when it was cold after showers from the northwest (clean N Atlantic ocean origin). The eyepiece / spider drum of my Dobson was quickly fogged due to moisture, but the sky was crystal clear.
And with temps barely above 0ºC the air can contain much less vapor than at 25ºC as in the tropics, where I don't have moisture problems, except at the beginning when I take out the cooler telescope from my air conditioned guesthouse room....

Anyway, DRW might have particulates and smoke from the Indonesian slash-and-burn of their tropical forests when the wind is west.
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Old 23-12-2017, 07:57 AM
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Interesting. I've always understood that humidity is a big contributor to a bad FWHM.
The atmosphere is a little thicker near the equator, though probably a negligible effect for our purposes.
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Old 24-12-2017, 05:13 AM
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erick (Eric)
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After four years in Israel, and as an observer, I wholeheartedly agree Glen. South of the Equator is the place to be, maybe as far north as 20 deg S if you want to get Andromeda at a bit of elevation.

Quote:
Originally Posted by glend View Post
As an imager i prefer complete access to the wonders of the southern sky, and believe around 30 degrees south is as far north as i would want to go. I grew up in the northern hemisphere and it just can't compete with the southern sky wonders. Imagers want their target objects to be up high enough to avoid looking through alot of atmosphere, so low angle targets like Andromeda are out anyway.
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Old 04-01-2018, 02:12 PM
anaxa (Syd)
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Best lat?

Hi All,
I agree with the comments that southern lats are best for viewing.
The problem as I see it is probably not the latitude, but where can you find a dark sky these days.
I live at 27 south on the eastern boarder just north of Brisbane and the light pollution is incredible and getting worse.
The other surprise to me was I purchased a EQ6 the other day only to find its made for the Northern Lats. I had to take to it with a grinder to take the edge on a stopping plate before it would go to my south at 27.
Anyway I am going to buy some land in the Simpson desert and view from there.
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Old 05-01-2018, 03:46 AM
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speach (Simon)
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pretty happy where I am 38 deg south nice view of the Southern sky, And really there is so much in the southern sky who need the north. Except I'd love to see M31!! only gets to about 10 deg here, oh! well there's always something!!!!
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