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General Astronomy >> Light Pollution

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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: Bortle scale accuracy? [Re: BrooksObs]
      #5952260 - 07/02/13 11:13 PM

Thanks for the answer, BrooksObs.

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BrooksObs
professor emeritus


Reged: 12/08/12

Re: Bortle scale accuracy? new [Re: derangedhermit]
      #5959507 - 07/07/13 07:52 PM

As further documentation concerning the limits of human vision, I just recently came across a couple of published papers presenting results of tests apparently conducted by the military addressing naked eye limiting magnitudes.

One paper, by the Office of Scientific Research and Development, cites a mean of +7.7 as "the faintest star visible with the unaided eye" based on their work.

Another paper, this one by Langmuir and Westendorp, indicated the "average" of their findings to also be +7.7, noting that subjects exhibited a range of 7.4-8.0 magnitude.

BrooksObs

Edited by BrooksObs (07/07/13 08:03 PM)


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Ekyprotic
super member
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Reged: 11/28/12

Re: Bortle scale accuracy? new [Re: BrooksObs]
      #5976757 - 07/17/13 08:20 PM

Thanks, Brooks! That woman you cited, the faintest stars she saw were three near 8.0? I wonder what percentage of the earth's surface actually has the ideal conditions necessary to see that dim.

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Ekyprotic
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Reged: 11/28/12

Re: Bortle scale accuracy? new [Re: Ekyprotic]
      #5976794 - 07/17/13 08:39 PM

Being from a highly light polluted area, and never having seen anything better than Mag 5.5 skies myself, when I simulate a Mag 8.0 sky in Starry Night Pro Plus, the sky is littered with stars- there actually seems to be more area covered by stars than there is black sky. Is this how the sky looks to you guys, or can you only see some/few of the 8.0 stars? I wonder what makes only some of the 8.0 stars visible and not the others (since they are all around the same brightness.)

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mountain monk
Carpal Tunnel
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Reged: 11/06/09

Loc: Grand Teton National Park
Re: Bortle scale accuracy? new [Re: Ekyprotic]
      #5977068 - 07/17/13 11:50 PM

In The Messier Objects, O'Meara says that on Mauna Kea, magnitude 8.5 stars are "within grasp of the naked eye..." (p.29) He also says the he "consistently detected stars as faint as 8.4 magnitude..." (p.31) The subject remains mysterious (for me), but then O'Meara probably sees better than an owl (some humans do).

Dark skies.

Jack


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Ekyprotic
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Reged: 11/28/12

Re: Bortle scale accuracy? new [Re: mountain monk]
      #5977236 - 07/18/13 03:36 AM

That's fascinating! I've heard that some parts of Antarctica may possibly be even more conducive to visual observation of extremely low magnitude stars (Dome C, Dome A, Ridge A). I wonder if either there or at other locations, with much younger eyes (the story related earlier, about children being able to view the Galilean moons of Jupiter unaided, is fascinating), even dimmer stars than Mag 8.5 could be glimpsed?

Dome C

https://en.wikipedia.org/wiki/Dome_C#Astronomical_observatory

Writing in the Proceedings of the Astronomical Society of the Pacific in 2005, Karim Agabi et al. discuss the suitability of the site for astronomy in terms of the seeing.[1] They determined the median seeing (measured with a Differential Image Motion Monitor placed on top of an 8.5 metres (28 ft) high tower) to be 1.3±0.8 arcseconds. This is significantly worse than most major observatory sites, but similar to other observatories in Antarctica. However, they found (using balloons) that 87% of turbulence was below 36 meters. A telescope built on a tower could rise above this "boundary layer" and achieve excellent seeing. The boundary layer is 200 metres (660 ft) at the South Pole and may be as low as 20 metres (66 ft) at Dome A.
In an earlier (2004) paper, Lawrence et al. considered the site and concluded that "Dome C is the best ground-based site to develop a new astronomical observatory".[2] This team measured superior seeing of 0.27 arcseconds, twice as small as at Mauna Kea Observatory. This figure was taken with an instrument insensitive to near-ground turbulence and so it is comparable to the 0.35 arcseconds Agabi et al. measured for "free atmospheric seeing".

Ridge A

https://en.wikipedia.org/wiki/Ridge_A

Ridge A was identified by a team of Australian and American scientists searching for the best observatory spot in the world.[1] The team leader described the site as "so calm there's almost no wind or weather there at all."[3] Ridge A is a low ridge of ice and has been estimated to have very low disturbances to visibility, such as thick atmospheric boundary layer, amount of water vapour and numerous others.
The site represents the "Eye of the Storm", whereby winds flowing off Antarctica in all directions appear to start from a point at Ridge A, where winds are at their calmest. It is also the site of a vortex in which swirling stratospheric winds high up and calm air at ground level combine to make it a place for viewing into space that is three times clearer than any other location on Earth.[4]
Researchers[who?] on the project suggested that photographs taken through a telescope at Ridge A could be nearly as good as those taken by the Hubble Space Telescope. Despite the difficult conditions on Antarctica and the remote location of Ridge A, construction costs for an observatory there that could match the Hubble telescope could be built at a fraction of the cost of sending Hubble into space.[4]


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BrooksObs
professor emeritus


Reged: 12/08/12

Re: Bortle scale accuracy? new [Re: mountain monk]
      #5977473 - 07/18/13 09:08 AM

Quote:

In The Messier Objects, O'Meara says that on Mauna Kea, magnitude 8.5 stars are "within grasp of the naked eye..." (p.29) He also says the he "consistently detected stars as faint as 8.4 magnitude..." (p.31) The subject remains mysterious (for me), but then O'Meara probably sees better than an owl (some humans do).

Dark skies.

Jack




Jack, in point of fact from an observing side-by-side comparison, I've repeatedly found that Steve has no better a detection limit for stars than that of many other highly experienced observers, including myself. This idea that a certain few individuals are born with some manner of special eye sensitivity is a total fiction, although one that is accepted by many hobbyists. The one distinct advantage that Steve does have in seeing particularly faint stars is the occasional opportunity to observe from a MUCH great altitude (Mauna Kea) than nearly any of the rest of us can reach.

As I've pointed out several times previously, any person with normal 20/20 or 20/15 vision is quite capable of matching the best of the best if only they were to gain the necessary observing experience and observe under "excellent" skies...both of which do not seem to prevail for perhaps 95% of today's amateur astronomers.

BrooksObs

Edited by BrooksObs (07/18/13 09:12 AM)


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Mr. Bill
Postmaster
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Reged: 02/09/05

Loc: Northeastern Cal
Re: Bortle scale accuracy? new [Re: BrooksObs]
      #5978043 - 07/18/13 02:32 PM

Interesting read...

I spend as many nights in northeastern Nevada as possible during observing season (all except winter) and find the skies to be as dark and transparent as anywhere I've been in the US. Seeing is fair most nights to very good on the best of nights.

My wide angle SQM (I just sent it back and had it recalibrated) shows darkness readings of 21.8-21.95 on good nights and on nights with low particulates the Milky Way does indeed cast shadows on the ground.

There are still dark places out there....you just have to be willing to rough camp to enjoy them.


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Ekyprotic
super member
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Reged: 11/28/12

Re: Bortle scale accuracy? new [Re: Mr. Bill]
      #5979181 - 07/19/13 05:27 AM

Brooks, maybe it wasn't his eyes that are extraordinary, but maybe the viewing location? Do you think a site like Mauna Kea or one of the locations listed in Antarctica could offer even dimmer stars for naked eye viewing? Or maybe, as you stated earlier, children and pre teens might be able to see dimmer stars because of their greater visual acuity?

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BrooksObs
professor emeritus


Reged: 12/08/12

Re: Bortle scale accuracy? new [Re: Ekyprotic]
      #5979339 - 07/19/13 08:34 AM

As I indicated, based on a direct comparison with others, Steve essentially doesn't "see" fainter than anyone else of equal experience and with good eyesight. So, given that he does have access to and often observes from sites of outstanding quality, it is logical to conclude that his gains are due to the skies, not his eyesight. At considerable elevation above sea level (as from somewhere up on Mauna Kea) the air is relatively thin, while also containing far less particulates from outside sources due to the vast surrounding ocean, and would offer much better transparency than the rest of us encounter.

However, I would still contend that many very young individuals with good eyesight are likely capable of seeing more than the best adults, based on empirical evidence.

BrooksObs

Edited by BrooksObs (07/19/13 08:37 AM)


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Ekyprotic
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Reged: 11/28/12

Re: Bortle scale accuracy? new [Re: BrooksObs]
      #5980901 - 07/20/13 05:04 AM

Thanks Brooks. I assume the same would be true of those sites in Antarctica or the Andes site that Tony Flanders was referring to, where Barbara Wilson (I hope I got the name right) saw every star in the second edition of Sky Atlas 2000.0

http://www.cloudynights.com/item.php?item_id=172

That would take us all the way down to Mag 8.5. But I wonder if the atlas went down to 9.0, maybe she would have been able to say that she saw stars even dimmer?

The reason I ask is that I am trying to put together a presentation on light pollution using Starry Night Pro Plus and I wanted to illustrate the different levels of pollution from the areas with the most light pollution to the areas with the least, and with the greatest transparency. I have even have panoramas of each specific site or city I am going to use (one for each level of the Bortle scale.) I'm going to use the Andes site that Tony Flanders mentioned as an example of the "perfect" dark site (although I could use Mauna Kea or Antartica also- as all the panoramas are either built into the program or can be made.) Absent of any proof that anyone has seen any stars of dimmer than Mag 8.5, I think I'll set that as the minimum magnitude for this site, just so people can have an idea of what the sky looks like from an amazing location like this. I was just wondering if very young eyes or an even better location (like the Dome A and C and Ridge A in Antarctica) could offer even deeper seeing, closer to Mag 9.0 visually. The number of visible stars rises exponentially even with small increases in limiting magnitude.

https://en.wikipedia.org/wiki/Apparent_magnitude

6.0 0.40% 4 800
No 7.0 0.16% 14 000
8.0 0.063% 42 000
9.0 0.025% 121 000
10.0 0.010% 340 000

Based on that CN review I linked to in the book, there are over 81,000 stars down to Mag 8.5..... if we could get it down closer to Mag 9.0 we would exceed over 100,000! It would be hard to comprehend what that would look like without actually being there, but a computer simulation helps. It's amazing that what we consider a dark site here in the northeast, that lets us see down to Mag 6.5, "only" lets us visually observe 9,500 stars, which is still only about 10 percent of what the perfect dark site would be capable of!


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Tony Flanders
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Reged: 05/18/06

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Re: Bortle scale accuracy? new [Re: Ekyprotic]
      #5980948 - 07/20/13 06:57 AM

Quote:

Thanks Brooks. I assume the same would be true of those sites in Antarctica or the Andes site that Tony Flanders was referring to, where Barbara Wilson (I hope I got the name right) saw every star in the second edition of Sky Atlas 2000.0.




Lake Titicaca is much higher than where Steve O'Meara observes in Hawaii. Even the top of Mauna Kea is very low altitude for the Andes.

Mind you, we're quibbling over small percents. BrooksObs is claiming 8.1 or 8.2, and Steve O'Meara and Barbara Wilson 8.4 or 8.5. I don't doubt any of these world-class observers, nor do I much care about the difference between 8.1 and 8.5.

I also don't believe that 95% of the world's population is capable of seeing stars of magnitude 7.5 even in ideal conditions.

Nor do I believe that light pollution is the main obstacle, for two reasons. First of all, sites that are effectively free of artificial skyglow at the zenith are actually very easy to find in the American West. And for me, skyglow becomes a fairly small obstacle to limiting magnitude even at fairly high levels of skyglow. I can't see significantly fainter stars from the black zone than from the blue zone.


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BrooksObs
professor emeritus


Reged: 12/08/12

Re: Bortle scale accuracy? new [Re: Tony Flanders]
      #5981149 - 07/20/13 10:19 AM

Quote:

I'm going to use the Andes site that Tony Flanders mentioned as an example of the "perfect" dark site (although I could use Mauna Kea or Antartica also- as all the panoramas are either built into the program or can be made.) Absent of any proof that anyone has seen any stars of dimmer than Mag 8.5, I think I'll set that as the minimum magnitude for this site, just so people can have an idea of what the sky looks like from an amazing location like this. I was just wondering if very young eyes or an even better location (like the Dome A and C and Ridge A in Antarctica) could offer even deeper seeing, closer to Mag 9.0 visually. The number of visible stars rises exponentially even with small increases in limiting magnitude.




Use caution in setting your planetarium magnitude limit. Computers are "dumb" when it comes to such situations and will produce exactly what is asked for without even considering mitigating circumstances.

Appreciate that even for highly experienced observers seeing stars of magnitude 8.0 or 8.5 is not a simple matter of just glancing skyward and there they are. It requires giving careful, sometimes lengthy, attention to spot such faint examples. Setting a planetarium to the same limits will likely generate a sky with FAR MORE stars than a real observer would perceive under the best of conditions.

For a more realistic depiction of the sky at a glance for such individuals I'd suggest making settings at least half a magnitude, or even a bit more, brighter than any absolute limit. Even then, as Tony points out, the majority of observers today are probably lacking in the needed observing experience necessary to "see" to their full potential. Proceed with care!

BrooksObs

As something of a P.S., let me also note that once the observer exceeds an altitude of say 11,000-12,000 feet lack of oxygen actually reduces just how faint he sees. Not all that much higher results in serious physical problems. There are stories of astronomers working at Mauna Kea without keeping their 02 masks handy finding themselves suddenly standing staring a the blank observatory walls right infront of them!

Conversely, use of 02 may enhanse the vision of some, resulting in either seeing fainter...or the illusion there of!

Edited by BrooksObs (07/20/13 10:33 AM)


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Mr. Bill
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Reged: 02/09/05

Loc: Northeastern Cal
Re: Bortle scale accuracy? new [Re: Tony Flanders]
      #5981150 - 07/20/13 10:20 AM

Let's remember that there is a limit to altitude and gains in visual acuity....anoxia trumps gains in scotopic vision.

My personal experience is spending time observing at the Barcroft Research Station in the White mnts. east of Bishop. It is 12500 ft altitude. I found that I could discern more subtle detail in low contrast extended objects when observing at the Grandview campground (8600 feet)located below the station. At that time I was using a pair of 25x150 Fujinon binoculars.


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mountain monk
Carpal Tunnel
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Reged: 11/06/09

Loc: Grand Teton National Park
Re: Bortle scale accuracy? new [Re: Mr. Bill]
      #5981333 - 07/20/13 12:14 PM

I would say the limit is 18000 feet. You can acclimatize to that altitude; people are born and live at that altitude. Their eyesight is acute. If they do have problems it is because of exposure to too much UV, though that was more of a problem in years past when they did not have access to sunglasses.

I spent about four years of my life at elevations from 11700 to 16000 feet and often went higher. I've lived at 6400 to 6800 feet under black and gray zone skies for decades. I am of the school that says the higher you go the better it gets and the more you see--if you are acclimatized.
I've been fortunate enough to observe from some very dark skies in the U.S.--the "boot heal" of New Mexico (the Gray Ranch), northern Death Valley (Eureka Dunes), and Beartooth Pass (on the border of Wyoming and Montana). I've also spent months at high elevation on the border of Peru and Bolivia, and in the western ranges of the Himalaya--the Kun Lun, Karakoram, Hindu Kush, and Pamirs. Much of the time I was at elevations of 15000 to 16000 feet. My judgement--and it can be no more than that since I was not carrying meters, etc.-- was that I saw more stars, a greater density of stars, at the higher elevations. I was well acclimatized--months at 12000 to 15000 feet.

I usually had clients or fellow mountaineers or military folks with me- probably a fairly normal cross-section of humanity. None has special training in astronomy or observing, but there were decided differences in how much they could see, either naked eye or through my 10x Zeiss binoculars.

Of course, this is merely anecdotal. In her book Celestial Sampler, Sue French has a story of an early explorer in Greenland who for a few moments could see more and fainter stars than the he could usually see--even under those (I assume) very dark skies. I have always believed in that possibility. Perhaps 9.0 is possible under very rare conditions, but I am aware of no proof, and I'm happy to accept other, more expert, opinions. As for subtle distinctions--between 8.1 and 8.4--I cannot say. I sure can't do that now. And in the past? Well, memory plays games with the mind.

Thanks to all for the interesting thread.

Dark skies.

Jack


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Mr. Bill
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Reged: 02/09/05

Loc: Northeastern Cal
Re: Bortle scale accuracy? new [Re: mountain monk]
      #5981589 - 07/20/13 03:09 PM

Quote:

I would say the limit is 18000 feet.
Jack




That's an astounding statement....

Detection of stars is one thing, stars are point sources, I was referring to edge detection of very low contrast extended objects...structure in dark nebulae.


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BrooksObs
professor emeritus


Reged: 12/08/12

Re: Bortle scale accuracy? new [Re: Mr. Bill]
      #5981651 - 07/20/13 04:05 PM

One must be cautious about just how much additionally the visual threshold increases with altitude beyond a certain point.

Indeed, there are small societies that survive up to altitudes of 15,000 to maybe 18,000 feet, but I cannot cite any observers from among those populations who can report about the advantages.

As far as the rest of us are concerned, I would note that above 10,000 feet the partial pressure of oxygen begins reducing to the point that it adversely affects the normal activities and functioning of the human body. In fact, the reactions of the average person begin to be impaired at an altitude of about 10,000 feet and for some people as low as 5,000 feet. The potential of altitude sickness and other effects quickly overcomes any visual advantage.

At 10,000 feet the observer is above 50% of the Earth's atmosphere, most of its moisture, and the vast percentage of atmospheric pollutants. Venturing higher probably would gain one very little further advantage and still have them remain fully functional. Thus, I would contend that 10,000 feet above sea level is about the break even point for "most" observers in gaining the greatest advantage in seeing absolutely as faint as possible.

BrooksObs

Edited by BrooksObs (07/20/13 04:15 PM)


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Mr. Bill
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Reged: 02/09/05

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Re: Bortle scale accuracy? new [Re: BrooksObs]
      #5981670 - 07/20/13 04:27 PM

That confirms my experience and those of whom I have first hand knowledge of.

Maybe Lance Armstrong and folks bred in extreme altitudes for generations have different results, but that is a very select population.



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JayinUT
I'm not Sleepy
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Reged: 09/19/08

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Re: Bortle scale accuracy? new [Re: BrooksObs]
      #5981812 - 07/20/13 06:38 PM

That goes with my experience though Jack by far has more experience than me at high elevation. I live at 5046ft and work at the same level. My observing sites are 1. 5336 ft and impacted to the NE by the Salt Lake City Light Dome, and it continues to grow and impact. The light dome from the Provo Metro area is also started to spread out over this site. It is a quick and easy site to hit with SQM-L measurements at around 21.53 to 21.55 at the darkest area. If I point toward the dome the iSQM-L drops to the mid 21.40's, so yes, the dome impacts the site. It's like having the summer Milky Way overhead and I won't share that impact to the SQM-L when I have the LP and the summer Milky Way.

2. Next site is my preferred observing area at 6097ft or 6396 ft (two locations down the dirt road but I call any gain form 200 feet minimal). and far enough from the Salt Lake Light Dome that the only impact is to 10 to 15 degrees if you go searching to the NE. SQM at Zenith and to the south at this site come in between 21.67 to 21.73 depending on the time of year. This site is a hour and twenty minutes form home and is U.S. Forest Land so it works nicely with unimproved camping but with toilets at a reservoir about 3 miles away. If I point at the SQM-L at the SLC Light Dome the reading decreases by about 5-7 points depending on the reading, based on my log records. This by far is the best site to observe at near to the Salt Lake City area. The question is for how long? I expect my observing career at age 48 will endure it for my lifetime but in the lifetime of my children I expect this site to drop off as development creeps westward from the Provo area and that light dome carries over to impacting the site more like the first site I listed. I also have another site down the dirt road that is at 6396 ft and adds a point or two on the SQM-L.

3. I have two sites in the Unita Mountains, one at 9978 ft and the other at 10203 ft. I usually use the 9978 ft site as its easier to get to, a shorter drive and during the week, I'm usually alone. Salt Lake City is about 100 miles west of the site and yes, it is now impacting the darkness of this site. SQM at this site is 21.60 to a high of 21.65 but usually around 21.63, that is where most of my recordings come in. It use to be higher, by about 6 to 8 points 10 to 12 years ago, but the light dome from SLC does impact. A good reason is these sites are closer to Salt Lake City than my favorite site and though higher and looking through less atmosphere, there is that LP impact. It seems a trade off of elevation for more LP. It's one reason I don't go there anymore that often. I will also say though that these readings are coming when the Summer Milky Way is above (can only use the sites in the summer) and so I can't measure what a fall, winter or spring reading would be. The site is open for snowmobiling but I don't do that hobby nor would I be up there on a cold winter's night, though I go to my 6096 site in the winter . . . and its cold there, but usually far less snow, like none (melts in a couple of days usually).

So I may gain over 3000 to 4000 ft between my primary sight and the mountain site, I'm not sure of that benefit. It prefer he darker skies with less impact from the SLC dome. I'll state up front living at 5000 ft means I don't find an adjustment for myself even at 10,000 feet. I do believe that helps and I believe one of the altitude projects in CO has done a study on this that if you live at altitude, you accumulate easier to a higher altitude than if your coming from sea level or near sea level.

So based on SQM-L readings do the light domes impact my observing? Surely. I can tell when I go to the first sight listed, 45 minutes from home over the darker site 1 hour and 20 minutes from home. Fainter objects have slightly more detail and at the other site, I have to work for that detail a lot harder. Fainter objects I wouldn't try at the first location like Hickson 79 which m 14" pulled in easily at the darker location that has far less impact from the SLC Light Dome.

My best location in Utah? Are there dark sites? Yep. The National Parks do a great job, Bryce, Arches, Canyonlands, Capitol Reef, and there is plenty of BLM land and Forest Land to go to that many outside of the Utah amateurs don't know about. I know many think these spots are great, and they are, and yes, they are dark. It's also a good 4-5 hour drive so that is a weekend trip with Friday off and driving down on Thursday for me. There is BLM land out by Canyonlands that I like but that is also getting an impact somewhat from Moab, not too bad, but it is increasing. I'll still go there as well or to Canyonlands.

In terms of dark areas though, I personally know many sites are kept quite here in Utah, just to keep people out of our favorite haunts. IF people ask, were happy to share and to be fair to me, I have a Google Map that shows the observing areas here in Utah, well most of them. A few I haven't put on yet. Two favorite that are within 4 hours, well more than two, Capital Reef, BLM Land in central Utah; BLM land near Canyonlands, and then The Wedge Overlook and Notch Peak (zero impact for any LP source and the highest SQM readings I've had). However, be ready to drive a good 3 to 5 hours to get to them and to me that means a long weekend of observing (which isn't a bad thing). However, that takes time and money and the average backyard and club outreach observer isn't going to do that on a regular basis and thus they never improve their observing skills. For that matter, in the first couple of site I mentioned, all are within 1 to 1.5 hours of Salt Lake City and yet many don't drive out to use these sites who are visual observers.

So I guess my point is that if your a serious observer and want to find dark skies or the darkest skies in your area, you find them. I also don't think too many people publish them and I think for the most part, the average person in the hobby to those well versed in the hobby won't go to those sites on a consistent basis and thus they fail to develop the experience needed to know when light pollution is impacting. That and I believe they don't comprehend why some people can spend forty-five minutes to an hour and a half on an object or set of objects to observe all the detail they can. They find it, view the object and off they go. Yes, a SQM meter and other tools can help to quantify the impact, but in the end, I think the experience and serious observer knows when LP is impacting their views. As time goes by it will become harder and harder for the visual observers of tomorrow, if there are enough to matter, to find sites like what have been and are available. I am convinced that the darkness of many sites now used will continue to degrade as we move closer to the year 2100. In truth, I wonder if the serious visual observer is going the way of the dinosaur, extinct?

One last item. In my own observing I have made pretty through notes of not only the impact of LP, but of haze and pollution on observing. It seems to me and I know the 3 years I've been gathering the data isn't long enough to quantify it, that pollutant particles that linger and hang in the air are also impacting the quality of observing. Has anyone else noticed that or is it just a local thing? Our population is expanding and will expand by around 60% by 2042. Utah is not good on decreasing pollution and so it lingers reducing observing conditions and again making it to where if you really want those views, you have to travel far away. Again, is it just local or anyone else seeing this and do you feel it also degrades the view of observing? For me it does. Thanks.


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Tony Flanders
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Re: Bortle scale accuracy? new [Re: BrooksObs]
      #5981882 - 07/20/13 07:25 PM

Quote:

At 10,000 feet the observer is above 50% of the Earth's atmosphere.




You are mis-remembering. Only 25% of the atmosphere is below you at 10,000 feet. The 50% mark is reached at 18,000 feet -- coincidentally around the limit of long-term human survival.

Even people with normal sea-level genetics can adapt pretty well to 10,000 feet in a few weeks. However, I have to suspect that even for people who are genetically adapted to high altitude, it's impossible to perform quite as well at 15,000 feet as at 5,000 feet. Any way you look at it, the body has to spend a bigger fraction of its energy budget pumping air through the lungs and blood.


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