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How much difference does elevation make in gazing?

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#1 mman22

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Posted 03 February 2013 - 10:19 PM

So I live in western Montana in a mountain valley. My home is approximately 4000 feet above sea level, however there is a mountain pass about 6300 feet ASL within about 30 minutes of me. How much difference in my quality of viewing would I notice with an 8" Dob? Also, I am starting to think of a summer trip to the Beartooth Pass which is 10,800 feet high, so knowing if it would be worth being there at night with my scope would be nice. Thanks for the responses!

#2 izar187

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Posted 03 February 2013 - 10:51 PM

High altitude can effect visual acuity. But it is an oxygen in the blood to the retina sorta thing, and I do not know where the number fall for this. Mountains and valleys can greatly determine local seeing conditions, due to prevailing winds, rising and falling air masses, temperature differences and such. Regional seeing may be the more important issue, and possible local observing site options to help countermeasure it.

#3 Jeff2011

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Posted 03 February 2013 - 11:12 PM

I think I read somewhere that 3000 to 4000 ft was optimal. You get the benefit of less atmosphere to look through plus still enough oxygen for your eyes to work efficiently. I am sure the experts here can correct me if my memory is incorrect.

#4 Allan...

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Posted 04 February 2013 - 01:16 AM

Hmmm.....how very interesting. I had never heard that O2 levels can affect eyesight but if true, I better stay down LOW...lol I AM bothered by oxygen deficiency at anything above 7000 feet; I know that for sure but mainly bothered by headaches. I always thought that the higher the better for seeing through the less dense atmosphere. Of course if you were doing astrophotography; that wouldnt be a problem. :)

#5 KWB

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Posted 04 February 2013 - 01:44 AM

I've been told by the individual who is in charge of the University of Denver's high altitude obsevatory atop of Mt Evans west of the city,that visual accuity is basically unaffected at observation below 11,000 feet in elevation. The DU observatory is at 14,260 feet and supplemental oxygen is used to help the staff and students retain sharp eyesight. FWIW,I have taken my telescopes to various locations around this state and believe I have observed without any perceived visual impairment as to my use of the scopes at 10,000 feet. That is my target elevation and the lack of light pollution in these rugged, rural areas is also a huge bonus. When the seeing is a Pickering 7.5 or greater,the experience is staggering IMHO. My destinations were mainly directed to locations on the west slope of the Rockies, and there are more nights of decent seeing possible than many think likely,especially those that have never experienced this type scenario. While this area of the U.S is never going to be comparable to high elevation locations along the Pacific coast or Hawaii as to consistent sky stabilty,most modern observatories are located in higher elevations if they are available and it's done for good reason,even if most obsevation today is done photographically. When the sky conditions permit,peering through less atmosphere to view your intended object is always a very good thing. The Hubble Space Telescope doesn't have peer through any.

I observe at 5,400 feet every time I venture out into my backyard and when the sky conditions are steady,the results are worthwhile for me as to increased sky transparency,meaning I can detect fainter objects. Despite the light pollution,on a calm night I can detect the star Mizar in Ursa Major isn't a singular one with naked eye vision,something I can't accomplish in another comparable urban setting at a considerably lower altitude.

It is my opinion that at about 3,000 feet in elevation, the sky begins a rapid transformation in transparency that steadily improves the higher one goes.

#6 Tony Flanders

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Posted 04 February 2013 - 06:14 AM

So I live in western Montana in a mountain valley. My home is approximately 4000 feet above sea level, however there is a mountain pass about 6300 feet ASL within about 30 minutes of me. How much difference in my quality of viewing would I notice with an 8" Dob? Also, I am starting to think of a summer trip to the Beartooth Pass which is 10,800 feet high, so knowing if it would be worth being there at night with my scope would be nice. Thanks for the responses!


This comes up periodically. The answer is: try it and find out. It all depends on local conditions.

The amount of air between 4,000 feet and 6,300 feet is negligible. However, valleys tend to accumulate pollutants, both natural and artificial. So it's likely that the mountain pass will have significantly better transparency. Again, only you can tell.

I doubt you'll get a significant improvement going from 6,300 feet to 10,800 -- and you'll have to contend with more cold, and (much more important) likely more wind. But again, only you can tell ...

If you live at 4,000 feet, you will experience zero loss in vision going to 6,300 and probably not too much going to 10,800. The optimal observing altitude no doubt varies depending on the individual, but it's probably well above 6,300 for almost anyone.

#7 mman22

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Posted 04 February 2013 - 08:25 AM

Thank you all once again. I did not think about the lack of oxygen affecting eyesight, although it makes sense with the amount of blood vessels in the eye. Tony makes a good point that acclimation makes a difference in how it affects you. Also did not consider the pollutant effect, another good point. Now I know why Tony is "Postmaster":) I will conduct a test in next few weeks a revisit this post with my results.

#8 Achernar

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Posted 04 February 2013 - 08:41 AM

Elevation does make a very big difference in what you can see. I live at most 200 feet above sea level, which means haze, fog and murky skies. When I went to the Okie-Tex Star Party in 2006 in the western tip of Oklahoma, I was shocked at how clear the sky was at an elevation of 5,000 feet above sea level. There is however two drawbacks to going higher in elevation. One is the thinning air, past 8,000 or 9,000 feet the decrease in ovygen weakens your vision. Then there is the cold, every 1,000 feet higher means 4 to 5 degrees colder temperatures. Going to a site nearly 11,000 feet up means very thin air, and bitter cold which will not improve your observing. If you have heart or lung problems, I advise against you going up there. Staying at 5,000 feet or so is a good comprimise between improved views and the effects of high altitudes on the human body. I would sooner go to the site you mentioned at 6,300 feet than at 10,800 feet just to get out of the haze and pollutants that tend to settle into valleys. I would think a mountain pass at 10,800 feet would also be subject to a lot of wind. In any case, I would be taking along very warm clothing, and something hot to drink too.

Taras

#9 Jon Isaacs

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Posted 04 February 2013 - 09:10 AM

Elevation does make a very big difference in what you can see. I live at most 200 feet above sea level, which means haze, fog and murky skies. When I went to the Okie-Tex Star Party in 2006 in the western tip of Oklahoma, I was shocked at how clear the sky was at an elevation of 5,000 feet above sea level.



I am sure the skies were much clearer in Western Oklahoma than in Mobile but I would have to think the difference was mostly due to the change of location and not the altitude. Getting away from the humid, hazy air of the Gulf of Mexico to the dry, western plains is a huge factor.

Jon

#10 Tony Flanders

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Posted 04 February 2013 - 09:37 AM

Elevation does make a very big difference in what you can see. I live at most 200 feet above sea level, which means haze, fog and murky skies. When I went to the Okie-Tex Star Party in 2006 in the western tip of Oklahoma, I was shocked at how clear the sky was at an elevation of 5,000 feet above sea level.


I am sure the skies were much clearer in Western Oklahoma than in Mobile but I would have to think the difference was mostly due to the change of location and not the altitude.


Quite so. The skies on the Pacific Coast, at sea level, are very prone to fog. But when they're clear, they're usually very clear indeed. Nobody who has experienced the dazzling sunshine of a California beach would call this area murky!

#11 csrlice12

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Posted 04 February 2013 - 10:15 AM

Elevation also has its drawback.....wind (especially if its cold), which isn't exactly condusive to great viewing. But on those dry, calm nights..........

#12 GlennLeDrew

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Posted 04 February 2013 - 10:30 AM

As hinted at already, airmass air quality is a much bigger factor than altitude. From the perspective of a mid-northern latitude dweller... A clean, post cold front sky at sea level is a heck of a lot better than a moist Gulf of Mexico airmass at 10,000 feet!

#13 Achernar

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Posted 04 February 2013 - 12:44 PM

Being within sight of the eastern slopes of the Rockies doesn't hurt, but there was NO haze whatsoever. It's also dry there, and wind rushing down from the Rockies pushes away fog and haze. However, that region does have one drawback, hurricane force wind apparently are common occurances there. I took this picture when I was there, there is no way I could have taken a 90 minute star trail photo like this near Mobile. The moisture in the air, plus the air pollution too scatter light and make the sky look like a dirty windshield compared to high and dry places I've been to.

Taras

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#14 Deb and Todd

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Posted 04 February 2013 - 01:56 PM

I review from the top of the Beartooth pass several time a year. Often go up there for meteor showers.

As others have said, it can often be cold and windy. Slightly down on the west side of the pass is long long. Often less windy and nice areas to set up the scope.

Viewing on the pass is pretty awesome though. No lights for miles and miles around. I often just get hooked on just using handheld 10x50 binoculars. The sheer number of objects that can picked up in binoculars alone is amazaing.

#15 Deb and Todd

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Posted 04 February 2013 - 01:56 PM

I review from the top of the Beartooth pass several time a year. Often go up there for meteor showers.

As others have said, it can often be cold and windy. Slightly down on the west side of the pass is long long. Often less windy and nice areas to set up the scope.

Viewing on the pass is pretty awesome though. No lights for miles and miles around. I often just get hooked on just using handheld 10x50 binoculars. The sheer number of objects that can picked up in binoculars alone is amazaing.

#16 mman22

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Posted 04 February 2013 - 08:30 PM

Hey Todd, I am a little jealous that someone beat me to this (but hardly surprising). Good point with the western slope, it is not as severe as the eastern side and does seem less exposed. I have been there during the daytime, but not at night. I can only imagine what the nighttime sky is like there. Have you ever done any gazing in Yellowstone?

#17 GeneT

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Posted 04 February 2013 - 10:44 PM

Ely, Nevada is about 6,400 elevation. I often viewed in lower valleys of about 4,000 and more than 8,000. I did not notice a great deal of difference.

#18 Deb and Todd

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Posted 08 February 2013 - 04:45 PM

mman22, mostly visit Yellowstone in the winter months. I do, however, spend labor day weekend in the park every year, staying at Bridge Bay campground. I always take one of my scopes to Yellowstone. Usually the 8" as I'm willing to leave it out unattended to cool and then leave unattended again when I go to bed. I will put away in the morning. Skies are very dark and viewing is generally very good. I will do a lot of binocular viewing in the park also.

However, near the campgrounds there are always people around carrying flashlights, car headlights, noise from other campers. While this does give oppurtunities for outreach, it is quieter and darker up on the pass.

Off the top of my head, I can think of many places a short drive from campgrounds where I could avoid the above issues. However, my overnight trips are with friends and family and I'd feel guilty, and my wife would be unhappy with me, if I abonded the group to go off for some viewing on my own. Our friends and family do enjoy short looks through to scope so setting up a 40-80 yards from the campground is good compromise.

#19 Gvs

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Posted 10 February 2013 - 12:02 AM

Mount Sajama in Bolivia SA.

Having more than half of the atmosphere below you provides views you can't describe with words. Here are a few examples at half that altitude.

http://www.sssp.org/...tro/index.shtml

Once you cross 9000 ft, breathing gets difficult and you need time to adjust. Basically your body requires to accumulate red blood cells. This takes up to four days. You get tired with very little effort.

Once you cross 15000ft your body does not cope as well, and it takes longer to adjust. If you have the time or live at 12000 ft you can accomplish it easily. After 15000 though, its an effort. Your eyesight eventually gets better though the physical effort is considerable.

My advice is stay within 13000 ft or below. There are many places through out the World where you can have spectacular views.

The advantages of altitude are:

- Lower and stable temp (capture more photons than temperature noise),
- No or very little wind (reduces convection, this depends on your site, high plateaus have less wind than peaks do),
- Extremely dry areas are better (low or no humidity - reduces convection),
- No light pollution, rules out most of the Eastern US (darker skies)
- Very few convection currents (less distortion at higher magnification)
- Reduced Rayleigh scattering (increases contrast, improves color).
- Less suspended particles in the air, less scattering. You have better contrast!

FYI .. the avatar is the Moon taken from Houston this year.

The following link is Omega at 9000 ft. in Cochabamba, Bolivia. Both from within city light pollution zones. Both photos were taken with the same equipment on different dates.

Posted Image

You can see the difference.



#20 GlennLeDrew

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Posted 10 February 2013 - 06:18 AM

While altitude does help, it's not the panacea the foregoing might suggest (which contains some meteorological simplifications, if not untruths.) The final arbiter on sky quality--as regards darkness--is the upper atmospheric airglow, at about 80km altitude. If you're in an already reasonably clean airmass, going up beyond a kilometer or so gains very little.

Again assuming a not 'gunky' airmass, putting half the atmosphere below you (at about 6km) does in no way result in an improvement by a factor of two (0.75 magnitude) on sky darkness. A 10% improvement--maybe 20%--(0.1-0.2 magnitude) improvement would be about it, with most of that gain occurring by a kilometer or so anyway.
.
Climbing for altitude is more useful for those in geographical locales where airmasses can linger and stagnate. And of course the high ground must lie within some accessible distance. The number of skygazers for whom the condition applies *and* its relief can be obtained is not large. Therefore a fresh airmass, often post cold front, is for most the only remedy.

The siting of observatories at high altitude locations is probably more to do with increasing the number of clear nights and obtaining steadier views (which requires specific conditions of geography and geographic latitude) than with gaining a 10% darker sky.

#21 BigC

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Posted 10 February 2013 - 01:48 PM

In my case have been considering rooftop or elevated platform to avoid the low-lying ground fog common here.Often there is a visibly dense layer about chest high above the ground.Yet the air above is much less foggy.One can see the effect over grassy fields early many mornings as well.I'm thinking getting above that might increase the number of viewing nights.

#22 RedLionNJ

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Posted 10 February 2013 - 04:46 PM

Totally depends on your purpose for going higher. Personally, with a very few exceptions, I've found seeing to be significantly poorer in mountain environments. Give me that sluggish, thick airmass for planetary viewing anyday. Once in a while you might get better seeing at altitude, but I'd take predictability over chance.

Grant

#23 Tony Flanders

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Posted 10 February 2013 - 07:46 PM

With a very few exceptions, I've found seeing to be significantly poorer in mountain environments.


Obviously, that's not always true -- there's a reason major observatories are built on mountaintops! A general rule of thumb is that the seeing is best at or near the top on the windward side of a mountain, and tends to be terrible in the lee. Which makes sense if you know anything about fluid flow. Think, for instance, of a boat's smooth bow wave and turbulent wake.






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