Jump to content


Photo

Bortle scale accuracy?

  • Please log in to reply
88 replies to this topic

#51 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 20 July 2013 - 04:04 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.cloudynig...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...arent_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!

#52 Tony Flanders

Tony Flanders

    Voyager 1

  • *****
  • Posts: 11208
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 20 July 2013 - 05:57 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.


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.

#53 BrooksObs

BrooksObs

    Viking 1

  • -----
  • Posts: 879
  • Joined: 08 Dec 2012

Posted 20 July 2013 - 09:19 AM

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!

#54 Mr. Bill

Mr. Bill

    Fly Me to the Moon

  • *****
  • Posts: 6296
  • Joined: 09 Feb 2005
  • Loc: Northeastern Cal

Posted 20 July 2013 - 09:20 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.

#55 mountain monk

mountain monk

    Surveyor 1

  • *****
  • Posts: 1949
  • Joined: 06 Nov 2009
  • Loc: Grand Teton National Park

Posted 20 July 2013 - 11:14 AM

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

#56 Mr. Bill

Mr. Bill

    Fly Me to the Moon

  • *****
  • Posts: 6296
  • Joined: 09 Feb 2005
  • Loc: Northeastern Cal

Posted 20 July 2013 - 02:09 PM

I would say the limit is 18000 feet.
Jack


That's an astounding statement.... :o

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.

#57 BrooksObs

BrooksObs

    Viking 1

  • -----
  • Posts: 879
  • Joined: 08 Dec 2012

Posted 20 July 2013 - 03:05 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

#58 Mr. Bill

Mr. Bill

    Fly Me to the Moon

  • *****
  • Posts: 6296
  • Joined: 09 Feb 2005
  • Loc: Northeastern Cal

Posted 20 July 2013 - 03:27 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.

:cool:

#59 JayinUT

JayinUT

    I'm not Sleepy

  • *****
  • Posts: 3933
  • Joined: 19 Sep 2008
  • Loc: Utah

Posted 20 July 2013 - 05:38 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.

#60 Tony Flanders

Tony Flanders

    Voyager 1

  • *****
  • Posts: 11208
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 20 July 2013 - 06:25 PM

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.

#61 mountain monk

mountain monk

    Surveyor 1

  • *****
  • Posts: 1949
  • Joined: 06 Nov 2009
  • Loc: Grand Teton National Park

Posted 20 July 2013 - 06:43 PM

Gentlemen: You all know far more about astronomy than I will ever know. I will only comment on "small societies..."

Because we live where we do, we have a somewhat limited idea of life at high altitude. A few factoids about places I have been, or been near to.

La Rinconada, Peru is a city of 30,000+ inhabitants at 16700 feet. Cerro de Pasco, Peru is a city of over 70,000 inhabitants at 14200 feet. Rongbuk Monastery, on the way to base camp for the north side of Everest, lies at 16340 feet. When I visited, it was still mostly ruins (destroyed by the Cultural Revolution), but was being rebuilt and is now occupied and can be reached by road. When the first British Everest expedition reached Rongbuk, in 1922, it housed 450 monks. In his book Himalayan Pilgrimage, David Snellgrove (London School of Oriental and African Studies and perhaps the preeminent authority on Tibetan culture of his generation) describes his travels to Dolpo, part of Nepal but Tibetan in culture. He describes villages at 16500 feet and says that several are higher. Petter Matthiessen describes them in his book The Snow Leopard, which won the National Book Award. I have spent time with Peruvian Indians and Tibetans and Sherpas at these altitudes and I have found no reason to believe their vision is inferior to our own. Going high with acclimatization, or living high, does not negatively affect vision. The body adapts. But that's only one half of the argument.

The other half is the argument that you can see more. Yes, of course, the law of diminishing returns sets in above...what? I cannot prove that you can see more, obviously. I will note that the Kun Lun Range is just south of the Taklamakan (various spellings) Desert, one of the driest places on the planet and very cold--well below zero in the winter. (And remote from light sources.) There, and in the Karakoram, you use camels, not yaks. I wish we had observations from there, but to my knowledge, we don't. I'll bet my cookies on a Tibetan kid born at 18000 feet and given a bit of training at observing... I wish I could do just that.

I concur with everything that Jay says.

Dark skies.

Jack

#62 BrooksObs

BrooksObs

    Viking 1

  • -----
  • Posts: 879
  • Joined: 08 Dec 2012

Posted 20 July 2013 - 08:18 PM

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. - Tony


From 3 separate citations I consulted: "6000-10,000 feet is the altitude range some people may start to experience problems related to altitude. AMS, or Acute Mountain Sickness symptoms may set in at any altitude above 6,000 feet. At 10,000 feet, the atmosphere is only 50% of that found at sea level."

BrooksObs

#63 mountain monk

mountain monk

    Surveyor 1

  • *****
  • Posts: 1949
  • Joined: 06 Nov 2009
  • Loc: Grand Teton National Park

Posted 20 July 2013 - 08:43 PM

Yes, but the key words here are "some" and "may."

Our company (I worked for them for over thirty years and was president) takes people up the Grand Teton. The typical client flies in from sea level or near sea level to 6000-7000 feet, spends two days in climbing school at 7000 feet, goes up to our hut at 11700 feet on the third day and climbs the Grand Teton--13700 feet-on the fourth day and returns to 6000-7000. Our rate of difficulties with AMS, after eighty years in business, is a small fraction of one percent. This is not to deny the possibility of AMS or its seriousness. I've had both forms--pulmonary and cerebral. It's serious but rare at the elevations you mention and not, I think, something that should concern most astronomers.

Dark skies.

Jack

#64 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 20 July 2013 - 10:12 PM

Thanks Brooks, Tony and everyone else! Lots of great info here :-) I'm going to set the planetarium to Mag 7.5 based on this. This answers my other question about elevation- would some place even higher than what the Andes can provide (like, near Mt Everest), be even better? (There's a Mt Everest panorama in SNPP.) I take it the answer is no, but not for the reason I thought..... I figured the light pollution from India to the south would be a problem. The Andes are in an ideal location, being close to the Pacific Ocean.

A related question to this I had was what is the FOV of the human eye? Based on what I've read it's close to 180 x 180 degrees, but I also read that to visually view stars that are dimmer than Mag 6, you need to concentrate on a much smaller FOV (I surmise this was along the lines of what Brooks was saying regarding what's necessary to see very dim stars.) It was recommended to make the starting FOV in the program 120 degrees.... which is where I have it. In any case, the program suffers from distortions if the FOV is greater than 167 degrees.

Sources:

http://clarkvision.c...resolution.html

http://www.astronomy...man-eye-fov....

http://www.astronomy...ha-detection...

160 x 175

http://en.wikipedia.org/wiki/Naked_eye

http://en.wikipedia....e#Field_of_view

I found the discussion about Peru particularly interesting because I was wondering if ancient cave art depicted astronomical objects that we can only see with telescopes now. I remember reading that Sirius B may be such an object.

I also read that the Nazca Lines may have been inspired by constellations (maybe Orion) and perhaps even the dark lanes in the Milky Way.

https://en.wikipedia...a_Lines#Purpose

my favorites are condor, giant, spider, dog and the monkey

https://en.wikipedia...al_significance

Dogon[edit]
See also: Nommo
The Dogon people are an ethnic group in Mali, West Africa, reported to have traditional astronomical knowledge about Sirius that would normally be considered impossible without the use of telescopes. According to Marcel Griaule's books Conversations with OgotemmĂȘli and The Pale Fox they knew about the fifty-year orbital period of Sirius and its companion prior to western astronomers. They also refer to a third star accompanying Sirius A and B. Robert Temple's 1976 book The Sirius Mystery, credits them with knowledge of the four Galilean moons of Jupiter and the rings of Saturn. This has been the subject of controversy and speculation. According to a 1978 Skeptical Inquirer article it is possibly the result of cultural contamination.[115] Some have suggested the contaminators to have been the ethnographers themselves.[116][117] Others see this explanation as being too simplistic.[118]



#65 JayinUT

JayinUT

    I'm not Sleepy

  • *****
  • Posts: 3933
  • Joined: 19 Sep 2008
  • Loc: Utah

Posted 20 July 2013 - 11:45 PM

I'll share a couple of links on altitude and people can read and do what they want with the info. I think we need to get back to discussing dark sites.

Wm Keck Observatory Link.

Institute for High Altitude Medicine Link

BaseCampMD.com

The site above lists this: High Altitude is 5000 to 11500 feet; Very High Altitude as 11500 to 18000 feet; Extreme Altitude above 18000 feet.

UIAA website

#66 Tony Flanders

Tony Flanders

    Voyager 1

  • *****
  • Posts: 11208
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 21 July 2013 - 05:09 AM

From 3 separate citations I consulted: "6000-10,000 feet is the altitude range some people may start to experience problems related to altitude. AMS, or Acute Mountain Sickness symptoms may set in at any altitude above 6,000 feet. At 10,000 feet, the atmosphere is only 50% of that found at sea level."


Gotta check your sources! That's especially true on the internet, where incorrect information propagates like wildfire. The first two statements are correct, the third is not.

#67 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 22 July 2013 - 06:46 AM

This is more of an academic question but does anyone have any idea what the limiting magnitude may be from outer space? Assuming that neither the sun nor the moon is visible from this position in space.

#68 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 01 August 2013 - 02:25 AM

Are there or have there been any reported naked eye sightings of the planet Neptune? I figured this would be a good target for those in areas of very little artificial light pollution as it is close to Mag 8 (7.78-8.00).

#69 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 01 August 2013 - 03:34 AM

Found this post from 1999 about a guy who can see down to Mag 8.5

http://tech.groups.y...tro/message/898

#70 JayinUT

JayinUT

    I'm not Sleepy

  • *****
  • Posts: 3933
  • Joined: 19 Sep 2008
  • Loc: Utah

Posted 01 August 2013 - 10:40 AM

One thing I have found in the hobby is that for 1 person that is vocal on their abilities, there are usually 2 or 3 that are not. So is viewing from 8.0 to 8.5 as rare as we might thing for the serious visual observer? Isn't it just possible that someone can do it and just isn't vocal about it, doesn't feel the need to share or just doesn't want to prove that they can do it. They know they can do it, they've done it and so for them that is enough? How many of these people are there in the hobby I wonder?

Edit: I don't mean to imply that being vocal or sharing is bad, or bragging. I think many people just share what they find and what they are capable of. However, I am suspicious that there are more people who can and do wonderful things and just don't publish them for whatever reason. Much like I know of several people that have done 12 or more of the AL programs but never put in for the reward. They know what they can do. Their close group of observing friends know what they can do and that is all that matters to them. So I think there are more out there than we may think who can push the limits.

#71 Tony Flanders

Tony Flanders

    Voyager 1

  • *****
  • Posts: 11208
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 01 August 2013 - 01:21 PM

So is viewing from 8.0 to 8.5 as rare as we might thing for the serious visual observer?


Yes. Amateur astronomy is a small world; if there were lots of people who could do this, I would know about it.

I think many people just share what they find and what they are capable of. However, I am suspicious that there are more people who can and do wonderful things and just don't publish them for whatever reason. Much like I know of several people that have done 12 or more of the AL programs but never put in for the reward. They know what they can do. Their close group of observing friends know what they can do and that is all that matters to them.


Sure, but among that close group of friends would be somebody I know, or somebody who knows somebody I know.

#72 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 01 August 2013 - 09:01 PM

Tony, I thought it was interesting how the person who wrote that piece said that his co-observer could see half a magnitude to a full magnitude lower than he could, at the same site, at the same time. So maybe there are some significant variances between people.

I've been scouring the net looking for any reports of naked eye observing of Neptune and have yet to find any. I have a thought......

Isn't it true that the human eye is particularly sensitive to red light? So is it possible that those very dim stars that some people can see are red stars? Maybe the reason why there are no reports of naked eye seeing of Neptune is because it's blue-green and the human eye isn't as sensitive to that color light as it is to red? Just an idea.....

#73 JayinUT

JayinUT

    I'm not Sleepy

  • *****
  • Posts: 3933
  • Joined: 19 Sep 2008
  • Loc: Utah

Posted 02 August 2013 - 12:33 AM

There's a lot out there on the limits of naked eye DSO's.

First is Brian Skiff's list of objects that have been seen at this link.

There is this threat over at Astronomy where a poster states that he can see M101 and M51 naked eye and the rebuttals to that claim. Link 2 I find that thread an interesting read.

In this report at this link, it is reported that Brian Skiff has seen M81 as "a threshold object."

Brian Skiff reports that from a true dark site the limit (for observing naked eye) from dark sites seems to depend strongly on visual acuity. I'll provide that link at the bottom on his comments on altitude.

In terms of Neptune, Brian Skiff at this link failed to find it in 2005, though he believes it should be "straightforward with patience from Chile or elsewhere in the south."

My take from this and from someone who regular observers at sites form 21.64 to 21.77 is that it takes a dark site like this and observing there from a regular basis to really begin to train the eye to see to its limits. That limit will vary depending on the person. I think you can gain experience from observing as often as you can, and for a long time, the more you do it the better trained the eye is. It helps when you start going to a dark site. However, regular and consistent training of the eye at a dark site, which Brian Skiff states is 21.5 arch seconds or better, enhances the training. I'd be most interested in hearing from Tony how observing in light pollution in his opinion also helps in visual observing.

In terms of observing at altitude I share what I found there from Brian. He states:

"However, for visual observing, if you go too high, you'll lose visual sensitivity simply because not enough oxygen is getting to your brain. The optimum altitude range seems to be from about 1500 up to perhaps 3000 meters (5000 to 9000 feet). Below 1500m, the amount of crud increases dramatically, and above 3000m most people have at least mild effects from lack of oxygen. Visual observing from Mauna Kea without bottled oxygen is pretty crummy. Remember that astro-observing is mostly at the threshold of acuity, so even small physiological effects from altitude (or ill health etc) will have pronounced effects on your vision in these circumstances. (When you're observing sometime at high power, try exhaling and not taking a breath for a good chunk of a minute: before you get dizzy, the eyepiece view will fade out and go grainy.) For what it's worth, acclimation to altitude appears to be independent of age, gender, or physical condition---but the genetic engineering necessary for high altitude living has already been worked out: they're called Bolivians!"

That quote and the one above is at this link. His findings go with what I find, though I don't find an impact on myself until I go well over 10,000 feet. That is why my FOR me, my maximum height is between 9000ft and 10000ft. I often observe between 6000 and 7000 feet.

Anyway, just sharing what I found in spending some time looking around and I look forward to others insights.

#74 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 02 August 2013 - 02:48 AM

Thanks! This is exactly the kind of research I find most interesting! What's the highest level of seeing that any site that you know of has attained? 22? Also, I find it quite interesting that it seems like a number of people have reported being able to see to Mag 8.5 but no one any higher than that, not even 8.6 or 8.8? Did you find any reports for anyone claiming to have gone beyond 8.5?

Another question I have is how does myopia affect the dimmest objects we can detect? My vision is 20/60 (20/35 in my right eye and 20/80 in my left eye)...... would this affect the minimum magnitude I can see by a significant amount? Unaided or with glasses? The funny thing is when I shut my left eye and just look through my right eye it actually feels like I am wearing glasses because my vision seems so much sharper.

#75 Ekyprotic

Ekyprotic

    Vostok 1

  • **---
  • Posts: 153
  • Joined: 28 Nov 2012

Posted 02 August 2013 - 02:57 AM

haha that was an interesting thread- that guy was talking about how someone having a porch light on 5 miles away drives him nuts and he doesn't have any sources of artificial light pollution within 10 miles of his house.

further down in the thread he said this:

One night here I went to ~900X with my 12.5" on Saturn and saw near photographic detail. I consider seeing like that night a once in a lifetime thing, but I still have my notes and remember it vividly.

and someone responded that he'd read that 9th mag stars had actually been seen visually from Mauna Kea?

Dave - I don't want to hyjack the thread but in Stephen O'Meara's book "The messier Objects" he mentions that he was able to see stars of 8.2 with the unaided eye while doing his research in HI on Mauna Kea (at 9,000'). He mentions that others with him have made similar (8th-9th) sightings in the world's best observing sites. So I'm assuming that for extended objects in the same seeing conditions, could it be possible to include M101, even with its very low surface brightness, as a naked eye object under the best of conditions? Mr Q








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics