22 replies to this topic

[starblue]

I am looking at 2 properties that are listed, according to Lorentz's LP maps, with SQM values of 20.03 vs. 19.63 (year 2023 values). I don't know anything about SQM numbers. Is there much difference between the two values, and can you characterize them in words (maybe Bortle value or zenith limiting magnitude)? Are they too close to town to consider as stargazing properties? One has a clear view to the south where there is no development and where none is likely to happen in the foreseeable future (it overlooks desert BLM land), the other is along the east edge of town with primarily subdivisions to the south (i.e. at least no light spillover from businesses). Even if the worse one is the one with no development to the south, would the south skies actually be darker there anyway *because* of that reason? I'm trying to locate stargazing spots nearer town to avoid driving hours to somewhere dark. (I suppose I should get an SQM meter.) 

[TOMDEY]

Big decision worth researching --- depending on your passion for the hobby. Best visit those locations and others... really the only way to decide. The 20.03 is a lot better than 19.63, but both are far from "decent" If you're able to find better that still satisfy your other non-astronomical needs, investigate. Once you buy the property and set up there --- you will have to live with that decision. The most common lament I get from my astronomy friends is, "If I had only known then what I know now --- I would have bought property here (pointing at a map) instead." By then (now) it's of course water under the bridge and their whining continues --- sometime for years.   Tom

[Tony Flanders]

I am looking at 2 properties that are listed, according to Lorentz's LP maps, with SQM values of 20.03 vs. 19.63 (year 2023 values). I don't know anything about SQM numbers. Is there much difference between the two values, and can you characterize them in words (maybe Bortle value or zenith limiting magnitude)? Are they too close to town to consider as stargazing properties? One has a clear view to the south where there is no development and where none is likely to happen in the foreseeable future (it overlooks desert BLM land), the other is along the east edge of town with primarily subdivisions to the south (i.e. at least no light spillover from businesses). Even if the worse one is the one with no development to the south, would the south skies actually be darker there anyway *because* of that reason? I'm trying to locate stargazing spots nearer town to avoid driving hours to somewhere dark. (I suppose I should get an SQM meter.) 

I think having good skies to the south trumps the difference between 19.6 and 20.0 by a fair margin. Yes, the sky to the south, where people in the northern hemisphere do 90% of their observing, might well be darker.

 

As Tom Dey says, the difference between 19.6 and 20.0 is quite significant -- and both are probably better than the backyards of most American stargazers. But neither can be considered dark by any objective standard. To give some specifics, I find that when the zenith reads 20.0 on my SQM-L, I can see the summer Milky Way with ease, but it exhibits very little detail. Likewise, I have no trouble spotting most of the Messier galaxies through an 8-inch scope, but it's almost impossible to see the spiral arms of even the brightest.

[sevenofnine]

If you have an iPhone, you can download the Dark Sky Meter app.. It uses your phone's camera to get a  SQM reading. Good luck! 

 

https://apps.apple.c...ter/id602989060.

[LDW47]

I am looking at 2 properties that are listed, according to Lorentz's LP maps, with SQM values of 20.03 vs. 19.63 (year 2023 values). I don't know anything about SQM numbers. Is there much difference between the two values, and can you characterize them in words (maybe Bortle value or zenith limiting magnitude)? Are they too close to town to consider as stargazing properties? One has a clear view to the south where there is no development and where none is likely to happen in the foreseeable future (it overlooks desert BLM land), the other is along the east edge of town with primarily subdivisions to the south (i.e. at least no light spillover from businesses). Even if the worse one is the one with no development to the south, would the south skies actually be darker there anyway *because* of that reason? I'm trying to locate stargazing spots nearer town to avoid driving hours to somewhere dark. (I suppose I should get an SQM meter.) 

 Those 2 SQM numbers are in the same category range so no difference in sky quality that you could detect, thats making it simple for you. In Bortle numbers which many long time astronomers don't go by they are both in Bortle Class 5. There is a chart maybe in WIKI that compares those numbers plus other info, I will find it and let you know.

Edited by LDW47, 22 March 2025 - 03:39 PM.

[LDW47]

I am looking at 2 properties that are listed, according to Lorentz's LP maps, with SQM values of 20.03 vs. 19.63 (year 2023 values). I don't know anything about SQM numbers. Is there much difference between the two values, and can you characterize them in words (maybe Bortle value or zenith limiting magnitude)? Are they too close to town to consider as stargazing properties? One has a clear view to the south where there is no development and where none is likely to happen in the foreseeable future (it overlooks desert BLM land), the other is along the east edge of town with primarily subdivisions to the south (i.e. at least no light spillover from businesses). Even if the worse one is the one with no development to the south, would the south skies actually be darker there anyway *because* of that reason? I'm trying to locate stargazing spots nearer town to avoid driving hours to somewhere dark. (I suppose I should get an SQM meter.) 

It is a Wiki site just called Bortle Scale in it there is a comparative table called ' dark - sky classifications ', have a look. Just google it.  ( en.wikipedia.org )

Edited by LDW47, 22 March 2025 - 03:36 PM.

[LDW47]

 

If you have an iPhone, you can download the Dark Sky Meter app.. It uses your phone's camera to get a  SQM reading. Good luck! 

 

https://apps.apple.c...ter/id602989060.

Its not even close in accuracy to an SQM-L meter, I think the SQM-L is still around $150 C - $100US or close, they are Canadian Made so ??

 

 

Edited by LDW47, 22 March 2025 - 03:47 PM.

[Starman1]

I am looking at 2 properties that are listed, according to Lorentz's LP maps, with SQM values of 20.03 vs. 19.63 (year 2023 values). I don't know anything about SQM numbers. Is there much difference between the two values, and can you characterize them in words (maybe Bortle value or zenith limiting magnitude)? Are they too close to town to consider as stargazing properties? One has a clear view to the south where there is no development and where none is likely to happen in the foreseeable future (it overlooks desert BLM land), the other is along the east edge of town with primarily subdivisions to the south (i.e. at least no light spillover from businesses). Even if the worse one is the one with no development to the south, would the south skies actually be darker there anyway *because* of that reason? I'm trying to locate stargazing spots nearer town to avoid driving hours to somewhere dark. (I suppose I should get an SQM meter.) 

Look farther afield.

Naked eye limiting magnitude for both, at the zenith, with averted vision, is in the range of 5.8-6.0.

That sounds good, but:

--Lorenz' maps are good for cross-comparison of sites, but all the figures are 0.2-0.3 magnitudes darker than the sites actually measure on the ground.

--It presumes perfectly transparent skies with no haze or clouds anywhere.

--Solar activity has appreciably brightened night skies everywhere on a frequent basis--at my dark site by ~0.25 magnitude consistently.

Put those together, and Lorenz's actual numbers are almost laughable right now.

My advice is to keep looking and see if you can find a site of 21.0 or darker (preferably darker).  You live in a state with some of the darkest and clearest skies in North America.

I suggest somewhere at least 50 miles from any town over 5000 people.

It looks like SE is the direction to head to get away from LV's lights.

https://www.cleardar...ml?Mn=telescope

[Keith Rivich]

 Those 2 SQM numbers are in the same category range so no difference in sky quality that you could detect, thats making it simple for you. In Bortle numbers which many long time astronomers don't go by they are both in Bortle Class 5. There is a chart maybe in WIKI that compares those numbers plus other info, I will find it and let you know.

I would have to disagree with this. While a .5 SQM difference is not huge it is quite noticeable. I can easily tell the difference at our site when the evening starts off at 20.4 and ends on 20.9. 

 

This also highlights the fallacy of the Bortle scale: a Bortle 5 site is much better then a Bortle 5.9 site, even though they are in the same band. 

[LDW47]

I would have to disagree with this. While a .5 SQM difference is not huge it is quite noticeable. I can easily tell the difference at our site when the evening starts off at 20.4 and ends on 20.9. 

 

This also highlights the fallacy of the Bortle scale: a Bortle 5 site is much better then a Bortle 5.9 site, even though they are in the same band. 

I don't think so from my long experience, I never said I condoned the Bortle numbers or tried to explain to the OP that various segments of the sky can be a different reading on any given night, thats what you are stretching when talking a few decimals here and there in my SQM-L world. The poster asked a fairly general question and I gave them a source to read up on, to do a bit of research, you say this and I say that based on lengthy actual experience I hope over skies up to SQM-L 22.05. When I view on any given night I take readings on at least 6 segments of the sky and as it progresses I continue with readings in the direction that I am viewing, all nite long.  PS:  I don't use Bortle but I reference it because many relate to the Bortle Scale, many don't even know what SQM is, unfortunately.

Edited by LDW47, 22 March 2025 - 05:19 PM.

[LDW47]

I think having good skies to the south trumps the difference between 19.6 and 20.0 by a fair margin. Yes, the sky to the south, where people in the northern hemisphere do 90% of their observing, might well be darker.

 

As Tom Dey says, the difference between 19.6 and 20.0 is quite significant -- and both are probably better than the backyards of most American stargazers. But neither can be considered dark by any objective standard. To give some specifics, I find that when the zenith reads 20.0 on my SQM-L, I can see the summer Milky Way with ease, but it exhibits very little detail. Likewise, I have no trouble spotting most of the Messier galaxies through an 8-inch scope, but it's almost impossible to see the spiral arms of even the brightest.

If you can see the summer mw with ease at 20.00 SQM-L I would love to witness that, I really would.

[LDW47]

I think having good skies to the south trumps the difference between 19.6 and 20.0 by a fair margin. Yes, the sky to the south, where people in the northern hemisphere do 90% of their observing, might well be darker.

 

As Tom Dey says, the difference between 19.6 and 20.0 is quite significant -- and both are probably better than the backyards of most American stargazers. But neither can be considered dark by any objective standard. To give some specifics, I find that when the zenith reads 20.0 on my SQM-L, I can see the summer Milky Way with ease, but it exhibits very little detail. Likewise, I have no trouble spotting most of the Messier galaxies through an 8-inch scope, but it's almost impossible to see the spiral arms of even the brightest.

If you and anyone else insists that you can see the Summer MW at SQM-L 20.00 other than a brighter band of overhead sky from the south with nothing to show in it I think you are giving less experienced newcomers or even unwary oldcomers a huge false impression and it gets their hopes up when they see the words Milky Way.  It sure would mine if I didn't know better, eh. Why would anyone want to lead that way in a discussion leading up to property acquisition based on better skies or not, for astronomy. Its beyond comprehension, my comprehension, really.

[LDW47]

I am looking at 2 properties that are listed, according to Lorentz's LP maps, with SQM values of 20.03 vs. 19.63 (year 2023 values). I don't know anything about SQM numbers. Is there much difference between the two values, and can you characterize them in words (maybe Bortle value or zenith limiting magnitude)? Are they too close to town to consider as stargazing properties? One has a clear view to the south where there is no development and where none is likely to happen in the foreseeable future (it overlooks desert BLM land), the other is along the east edge of town with primarily subdivisions to the south (i.e. at least no light spillover from businesses). Even if the worse one is the one with no development to the south, would the south skies actually be darker there anyway *because* of that reason? I'm trying to locate stargazing spots nearer town to avoid driving hours to somewhere dark. (I suppose I should get an SQM meter.) 

Make sure you get the SQM-L model, the property that I would be interested in would be is the first parcel you mention and the skies should be considerably darker if checked with the SQM.  Now remember i have never laid eyes on the land but a south exposure can show a lot of goodies between SE & SW. And the Big Dipper and Cassiopia is high enough in the north to give you some pretty nice views even looking over some lights.  IMHO !

[Tony Flanders]

I would have to disagree with this. While a .5 SQM difference is not huge it is quite noticeable. I can easily tell the difference at our site when the evening starts off at 20.4 and ends on 20.9.

The difference between 20.4 and 20.9 is quite a bit bigger than the difference between 19.5 and 20.0. And the difference between 21.2 and 21.7 is monumental.

[Tony Flanders]

If you and anyone else insists that you can see the Summer MW at SQM-L 20.00 other than a brighter band of overhead sky from the south with nothing to show in it I think you are giving less experienced newcomers or even unwary oldcomers a huge false impression ...

Are we perhaps using different words to say the same thing? I said "I can see the summer Milky Way with ease, but it exhibits very little detail." You say "a brighter band of overhead sky ... with nothing to show in it."

Frankly, I think you're spoiled by living in a dark location. Though even there, the full Moon will drive SQM-L readings up way brighter than 20.0.

Let's just say that I have lots of experience viewing faint objects under bright skies, because that's the circumstances that life dealt to me. I can in fact detect the summer Milky Way with some effort when my SQM-L reads 19.0, so it seems quite bright to me at 20.0 by comparison. I agree that most beginners would likely not notice it at first, but I'm sure they would have no trouble after I explained what they're looking at.

 

Typical SQM-L readings at my astro club's exurban observing field range from about 19.6 to 20.0, so I have a huge amount of experience with that level of skyglow. As I said before in this thread, I have little trouble detecting all the Messier objects even through small telescopes, but with a handful of exceptions none of the galaxies exhibit much detail even through the fairly large scopes that many of the members own.

[LDW47]

The OP states that they are not at all familiar with SQM / Bortle numbers and their related meaning. I don't think it is a help in their purchase of property and the ensuing skies / viewing. Espousing that differences of mere decimals affect the viewing quality / level is misleading in a realestate acquisition, in my honest opinion. They will think they are gaining more but they aren't, sometimes as usual it will be a bit better in one direction and sometimes worse in another and the bright moon is always another story even in SQM 22.00 skize. They were given a range of numbers that  indicate a single range of sky quality which can vary on any given nite between individual sections of the sky, thats not in question and sometimes you can luck in and find the numbers have jumped up to the next level or down to a lower level. But as to the issue of property purchase what do you count on by being told that one end of a single range is much better than the other its such a fine line that it can change in minutes if not seconds. As I mentioned to the OP they had better research what sky quality means and Bortle scale as well in relation to their astronomical needs and where they purchase property, better to wait before you jump into something thats not. I mentioned that the south facing, open land appears to be the much better of the two described but I haven't laid eyes on it so its just my thoughts speaking. If I was the OP I would get out there on several of the more darker nites and do a thorough accessment with my own eyes and maybe even with a newly acquired SQM-L and an experienced friend maybe. If I was shooting to improve my viewing location I would want SQM-L 21.3 as my minimum but I'm not trying to discourage, really, just my experience talking, eh. Good Luck to them, we only come around once in the journey !

Edited by LDW47, 23 March 2025 - 09:08 AM.

[Starman1]

Looks like skies are very dark only 40-50m SE of St.George.  That's where I'd look for land.

Also, the south is wide open and dark at that point.

Remarkably dark skies are surprisingly close.

That is less than an hour's drive.

 

I could only dream of that here in So Cal.

[daveb2022]

 If I were moving to support my astronomy hobby, besides transparency and darkness levels, I'd kinda want to know how steady the skies are on average. No?

 

 

There are class 1 or 2 skies I visit regularly, and some of them rarely have stable enough skies to observe. The crystal clear dark skies at those spots does not help. Drive 50 miles away and bliss...much better seeing and just as dark.

 

With my SQM-L, the average local city LP registers 17.50-18.70. A good night for my location is anything above 18.50. There is a huge difference between 18.50 and 18.70 in my neck of the woods. Most of the time, it seems my SQM reading mimics the transparency conditions and NELM, but not always. Last night I had poor NELM but above average SQM reading at 18.40-18.50. I was surprised I was able to see some of the dimmer magnitude objects when the sky appeared compromised.

[LDW47]

 If I were moving to support my astronomy hobby, besides transparency and darkness levels, I'd kinda want to know how steady the skies are on average. No?

 

 

There are class 1 or 2 skies I visit regularly, and some of them rarely have stable enough skies to observe. The crystal clear dark skies at those spots does not help. Drive 50 miles away and bliss...much better seeing and just as dark.

 

With my SQM-L, the average local city LP registers 17.50-18.70. A good night for my location is anything above 18.50. There is a huge difference between 18.50 and 18.70 in my neck of the woods. Most of the time, it seems my SQM reading mimics the transparency conditions and NELM, but not always. Last night I had poor NELM but above average SQM reading at 18.40-18.50. I was surprised I was able to see some of the dimmer magnitude objects when the sky appeared compromised.

Steady skies can only do so much if you are in a low SQM-L viewing area, from my experience. What are you thinking when you say steady skize, eh. Do you mean the number of viewable nites available over the year due to climate / weather patterns. That may narrow the area of search down, restrict it considerably, ya think. What is the difference in actual views between 2 decimals of SQM-L.

Edited by LDW47, 23 March 2025 - 03:00 PM.

[daveb2022]

Steady skies can only do so much if you are in a low SQM-L viewing area, from my experience. What are you thinking when you say steady skize, eh. Do you mean the number of viewable nites available over the year due to climate / weather patterns. That may narrow the area of search down, restrict it considerably, ya think. What is the difference in actual views between 2 decimals of SQM-L.

...Living in Ca, some of my better observing of Jupiter has been in heavy smoke in bright LP. I have been is places where the sky is ultra dark and clear, but the seeing is horrible. Often not much is worth observing. 

If you only had a week worth of steady skies a year, personally, I wouldn't want to move there just because of dark skies. These are places you probably wouldn't see an observatory. I'd be looking elsewhere for spots that support clear steady dark skies more often than not. JMO.

What is the difference in actual views between 2 decimals of SQM-L? As I posted there is a huge difference between 18.40 and 18.50. I might not be able to detect a mag 12.5 galaxy in 18.40 skies but might in 18.50 skies. I can visually see the difference in open cluster star counts as well. But poor seeing might wipe out those same objects even in darker skies. It's a balancing act. I don't have much data on dark sites. I (usually) observe from home in what others classify as B7 or B8. I only started using a SQM about 4 years ago. I've always judged skies by NELM and what it looks like through the scope.

Edited by daveb2022, 23 March 2025 - 09:57 PM.

[ABQJeff]

You are in Utah!  21.9 Mpsas or bust, plenty of land in SW US with those skies.  Look up DJ Lorenz light pollution map, go grey or black.  Many great spots towards Lee’s Ferry, Moab, etc.

[LDW47]

...Living in Ca, some of my better observing of Jupiter has been in heavy smoke in bright LP. I have been is places where the sky is ultra dark and clear, but the seeing is horrible. Often not much is worth observing. 

If you only had a week worth of steady skies a year, personally, I wouldn't want to move there just because of dark skies. These are places you probably wouldn't see an observatory. I'd be looking elsewhere for spots that support clear steady dark skies more often than not. JMO.

What is the difference in actual views between 2 decimals of SQM-L? As I posted there is a huge difference between 18.40 and 18.50. I might not be able to detect a mag 12.5 galaxy in 18.40 skies but might in 18.50 skies. I can visually see the difference in open cluster star counts as well. But poor seeing might wipe out those same objects even in darker skies. It's a balancing act. I don't have much data on dark sites. I (usually) observe from home in what others classify as B7 or B8. I only started using a SQM about 4 years ago. I've always judged skies by NELM and what it looks like through the scope.

Each have our own issues, I have been blessed with SQM-L 22.00 skies for 50 yrs, at my remote camp, even then you have nites where those skize don't perform as normal, its the nature of the beast, for various reasons. My backyard at my home is average 19.50-20.50, its the same situation and as we both know various segments of a nights sky can vary considerably on any given nite incl at my camp, thats how I point my SQ meter. The Milky Way high overhead is a big demon, the meter drops down a few numbers when you point there and etc. But I will never say I can detect differences in seeing targets when numbers change a couple of decimals, I am just not that competent I guess. Or my eyes aren't that sensitive. As to the OP's final decision, of where they want to put their scopes down, its their choice, as always. As you must also know they have new subdivisions built under those exceptional skies dedicated to astronomy, to astronomers but maybe the OP doesn't want to bear the cost, maybe. You will have to ask them directly why they chose the two locations they described.

Edited by LDW47, 23 March 2025 - 10:38 PM.

[daveb2022]

Well I agree with Tony's posts. I would suggest the OP ask others (if any) in the area what the average conditions are. I would hope to find a spot which produces transparent skies, steady skies (reasonable Pickering levels), and dark skies...in that order more than likely. Between the two spots, I'd choose the one with better seeing and transparency even if it was slightly brighter. I'd probably want as much access to 360 degree open skies, but also agree that a southern exposure would be my choice if I had to choose.