Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Difference between Bortle 2 and 1

  • Please log in to reply
48 replies to this topic

#1 Jsg

Jsg

    Sputnik

  • -----
  • topic starter
  • Posts: 39
  • Joined: 23 Dec 2020
  • Loc: Northern Sierra Mountains, 4,000 ft.

Posted 26 April 2021 - 09:10 AM

I suppose I am very fortunate to be in a location described as Bortle class 2, in the California Northern Sierra Mountains. I'm a newbie with a 12" Dobson. I would not have to drive far to get to campgrounds shown as Bortle 1 on the maps. Not that I'm dissatisfied with the good seeing I have at home, but just wondering from a technical standpoint, would I see a noticeable difference in a Bortle 1 location? I'll post lat and long for two different locations if someone wants to slice the numbers. My main interest is DSOs- nebulae and galaxies. Worth the 2-1/2 hour drive to get out of my horribly light polluted Bortle 2 location?

#2 alphatripleplus

alphatripleplus

    World Controller

  • *****
  • Moderators
  • Posts: 123,348
  • Joined: 09 Mar 2012
  • Loc: Georgia

Posted 26 April 2021 - 09:31 AM

 I wish I had first had experience to answer this question, but it has been a long time since I last experienced Bortle 2 skies, and I don't ever recall being  under Bortle 1 skies.



#3 Traveler

Traveler

    Soyuz

  • *****
  • Posts: 3,725
  • Joined: 19 Aug 2007
  • Loc: The Netherlands

Posted 26 April 2021 - 09:42 AM

I think the difference between the two situations is quite noticeable. However, when i can choose between Bortle 2 at high altitude and Bortle 1 on less high altitude i would choose for the Bortle 2....

But hey, i would be very very happy with a Bortle 2 sky anyway...cool.gif

 

The best skies i ever saw was in Nepal at 5500m Bortle 1...but there on that altitude it was so cold and i was already so tired after weeks of hiking and other things that i was not able to enjoy the sky...

 

Much more enjoyable was at an altitude of  "just" 4700m...There i saw M33 for example with naked eyes...I didnt belive it was M33 first...It was such a big object...It was amazing... 


  • davelpg, Augustus and BradFran like this

#4 Phillip Creed

Phillip Creed

    Idiot Seeking Village

  • *****
  • Posts: 3,775
  • Joined: 25 Jul 2006
  • Loc: Canal Fulton, OH

Posted 26 April 2021 - 09:44 AM

I don't think it's worth it, but there are some caveats

The biggest noticeable difference would be any light pollution right along the horizon.  A Bortle 1 would have zero light pollution no matter what direction you looked.  I've seen this in the Big Bend region of Texas in 2005 and 2008.

The zenith won't be much different between Bortle 2 and Bortle 1.  You might notice you get a bit further from the Bortle 1.  It would only come into play on "threshold objects" (think faint spiral arms).  You might notice things you can just see with averted vision from Bortle 2 are easier to visually "hold" from Bortle 1.

I think the bigger difference is along the horizons.  A Bortle 2 might have noticeable light domes along the immediate horizon, possibly brightening the sky up to 10° or so in altitude.  Almost any target you'd care to look for (minus, say, Omega Centauri) would be well above this level, anyway.

Generally speaking, I wouldn't drive an hour for a dark sky site unless it's at least two Bortle classes better.  You'd basically be going 2-1/2 hours just to squeeze out that last little bit of sky darkness.

To say you did it at least once, yeah; it'd be worth it.  On a routine basis, though, when you're already starting at Bortle Class 2?  Debatable.

Clear Skies,

Phil


  • jdupton likes this

#5 Jsg

Jsg

    Sputnik

  • -----
  • topic starter
  • Posts: 39
  • Joined: 23 Dec 2020
  • Loc: Northern Sierra Mountains, 4,000 ft.

Posted 26 April 2021 - 10:07 AM

Thanks Phil et al. I may eventually make the trip, but first do as much deep sky observing as I can here to get a sense of my real limits, so I'll know the real difference out in the desert. One difference between the two locations I have in mind is that at home, Bortle 2, I am surrounded by green forest which, I've read, absorbs daytime heat and thus less nightime heat dissipation to disturb seeing. Whereas the Bortle 1 locations near me are all open desert with exposed soil, which has higher heat absorption and so greater possibility of lesser seeing. Just what I've read, not based on practical experience.

Bur for those of you looking for a relatively easy access Bortle 1 site, if you are willing to fly, here's a possibility- fly into Reno Nevada (USA), drive north on highway 395 for 2 hours to appropriately named Moon Lake which has a campground. It's on the western edge of the largest Bortle 1 area in the continental US, the Great Basin of Nevada. I've never been to this campground but will report if I do. Correction- no campground at Moon Lake, but nearby camping at Blue Lake and Valley Reservoir.

Edited by Jsg, 26 April 2021 - 02:14 PM.


#6 MarMax

MarMax

    Apollo

  • *****
  • Posts: 1,107
  • Joined: 27 May 2020
  • Loc: Los Angeles

Posted 26 April 2021 - 11:14 AM

Since you are in California there is a small town called Darwin that's off 395 about 40 minutes East of Olancha. This is my go-do dark site but it's about a 4 hour drive from home.

 

On 4/12/2021 the SQM measured with my Unihedron SQM-L was 21.99 and 22.00 with back to back measurements at 2 am. I think this would technically be considered Bortle 1 and there was a very slight hint of a light dome from Ridgecrest.



#7 Jsg

Jsg

    Sputnik

  • -----
  • topic starter
  • Posts: 39
  • Joined: 23 Dec 2020
  • Loc: Northern Sierra Mountains, 4,000 ft.

Posted 26 April 2021 - 11:34 AM

Marmax- Darwin looks like a good go-to spot for those living in LA or the area. The map I looked at showed it borderline Bortle 1 and 2, with that distinction we are splitting hairs with a measuring system that is intrinsically fuzzy. Maybe I should get one of those meters, but I'm saving for Televues, if you know what I mean.

#8 Jsg

Jsg

    Sputnik

  • -----
  • topic starter
  • Posts: 39
  • Joined: 23 Dec 2020
  • Loc: Northern Sierra Mountains, 4,000 ft.

Posted 26 April 2021 - 11:45 AM

But I wonder- if there is so much as a hint of light dome on the horizon- does that mean your seeing is at all compromised- Phil (above) thinks not on zenith but yes on horizon. Perhaps splitting hairs at this point, but it's worth wondering what advantage there is to seeking a location entirely away from any extra light. With a 12" Dob, trying to see galaxies at 12 or dimmer, and trying to see spiral arms with any contrast, it's an intriguing question. Of course I'd probably see more at home at 4,000 feet in forest at Bortle 2 with a 20 or 24" Dob than I would see at a Bortle 1 bare desert at 2,000 feet with a barely portable 12" Dob.

#9 BradFran

BradFran

    Apollo

  • -----
  • Posts: 1,029
  • Joined: 12 Jul 2017
  • Loc: Villingen-Schwenningen, Germany

Posted 26 April 2021 - 12:18 PM

I'll echo Traveler's comment... altitude and seeing under Bortle 2 conditions are better than looking through a lot of atmosphere under Bortle 1 conditions.

 

Depending on where you are in northern California, you might check out my favorite observing spot, Bumpass Hell parking lot in Lassen Volcanic National Park. It's also probably only Bortle 2 because of small light domes from Chico and Red Bluff and some sky glow from Redding, there are no direct lights. It has frequent good seeing at 8200'. The Milky Way can cast shadows and Jupiter causes light pollution worse than the light domes. 7th magnitude stars are everywhere in direct vision (I've gone down to 7.5 when things were perfect), the Milky Way is mottled with detail and M33 is completely obvious. When the seeing cooperates it's magical. Check the conditions before going as the road is usually covered in snow until sometime in June. I haven't been there in a few years and hope it stays dark.

 

I'd love to have the comforts of home under Bortle 2 skies! No setup and take down of the telescope each session... get some wheely bars and slide it in and out of a shed and done. I think if there is no light shining directly into your vision, the sky glow from a small dome does little harm unless you stare at it. 4000' is above the worst of the atmosphere and you won't have any issues with acclimation due to altitude or having to camp.


Edited by BradFran, 26 April 2021 - 01:04 PM.


#10 MarMax

MarMax

    Apollo

  • *****
  • Posts: 1,107
  • Joined: 27 May 2020
  • Loc: Los Angeles

Posted 26 April 2021 - 02:12 PM

Yes, I would love to have the problem with only Bortle 2 skies at home . . lol.

 

And altitude is definitely important. Darwin is at about 4,500 feet so not bad but not as good at 7,000-8,000 would be.

 

And the faint light dome on the horizon also happened to be in the direction of Omega Centauri, which is most definitely not a faint object, but it would have looked better without that hint of light dome. I was observing with an AT130EDT.



#11 Jsg

Jsg

    Sputnik

  • -----
  • topic starter
  • Posts: 39
  • Joined: 23 Dec 2020
  • Loc: Northern Sierra Mountains, 4,000 ft.

Posted 26 April 2021 - 02:29 PM

Yes- poor little me having to suffer Bortle 2 skies out my front door- but the perfectionist in me is curious. I'm close to Lassen and had disregarded it because it is Bortle 2, but as you say Bradfran, Bortle 2 at 8,000 ft is probably better than Bortle 1 in the soup of lower elevation. I've added Lassen to my list. As well, I intend to search northwest Nevada and southeast Oregon for an accessible location over 6,000 ft in Bortle 1 which is everywhere in the desert there. Would be nice to find an 8,000 ft accessible location no light pollution cool temperatures dry air no mosquitoes and a ready supply of beer. Asking too much? Maybe I should move to the Andes.
  • MikeTahtib and MarMax like this

#12 Symui

Symui

    Vostok 1

  • -----
  • Posts: 187
  • Joined: 28 Mar 2008
  • Loc: 37.9,-121.9 - Northern California

Posted 26 April 2021 - 02:55 PM

All things equal, Bortle 1 will beat Bortle 2 but conditions are rarely equal even at the same site over multiple nights. 

 

For me, altitude and sky conditions are key when comparing B1 vs B2 locations. For instance, a B2 location I frequent east of Bishop at 8300' almost always beats a B2 location near Adin at 4000'.  The B1 location near Likely at 4000' sometimes beats the B2 near Adin but not always.   Usually sky conditions are the determining factor between these two sites.  However, move further east of Likely at a slight higher elevation (500 to 1000' higher) and it almost always beats Likely or Adin.    The good news for you is bortel 2 skies right outside your door are going to be significantly better than most folks "dark" site. 

 

Would you see a noticeable difference at the B1 site? 

 

My guess - probably.  Definitely worth a drive to find out.   One problem with campgrounds are LED lights from other campers.   I suggest getting a BLM map for the county you're considering and observe on the BLM land as opposed to the campground to avoid the camper lights.    I usually camp and observe on BLM land but depending on the location will sometimes use a campground as a base camp and observe on the BLM land.

Either way let us know how the B1 skies compare to your B2 location.


  • BradFran likes this

#13 Jsg

Jsg

    Sputnik

  • -----
  • topic starter
  • Posts: 39
  • Joined: 23 Dec 2020
  • Loc: Northern Sierra Mountains, 4,000 ft.

Posted 26 April 2021 - 03:13 PM

Tioga Pass, Yosemite National Park, highest highway pass in the Sierras, just under 10,000 feet, Bortle 2. I'll let you know if I get there with a scope.

Forester Pass on the Pacific Crest Trail between Kings Canyon and Sequoia Parks is 13,000 ft and Bortle 2. Wonder if anyone has ever packed in a large scope to a high elevation like this. Won't be me.

Edited by Jsg, 26 April 2021 - 03:16 PM.


#14 LDW47

LDW47

    Cosmos

  • *****
  • Posts: 8,366
  • Joined: 04 Mar 2012
  • Loc: North Bay,Ontario,Canada

Posted 26 April 2021 - 04:18 PM

I suppose I am very fortunate to be in a location described as Bortle class 2, in the California Northern Sierra Mountains. I'm a newbie with a 12" Dobson. I would not have to drive far to get to campgrounds shown as Bortle 1 on the maps. Not that I'm dissatisfied with the good seeing I have at home, but just wondering from a technical standpoint, would I see a noticeable difference in a Bortle 1 location? I'll post lat and long for two different locations if someone wants to slice the numbers. My main interest is DSOs- nebulae and galaxies. Worth the 2-1/2 hour drive to get out of my horribly light polluted Bortle 2 location?

I wouldn’t drive 2 1/2 hrs to and 2 1/2 hrs. back for that difference and I am under Bortle 1 skies at my remote camp all summer long. If I were you I would be happy with your skize unless you just want to for a change !


  • viewer likes this

#15 Jsg

Jsg

    Sputnik

  • -----
  • topic starter
  • Posts: 39
  • Joined: 23 Dec 2020
  • Loc: Northern Sierra Mountains, 4,000 ft.

Posted 26 April 2021 - 06:22 PM

Thanks LDW47. I'm in the hobby as much out of technical interest in the capabilities of hobbyist instruments as I am for interest in the cosmos. But I think it's obvious I have little to gain from seeking B1 locations. First I need to learn to use what I have where I have it, then maybe I'll experiment with distance locations just to see how much difference it really makes. Meanwhile, it's cloudy tonight.
  • LDW47 likes this

#16 LDW47

LDW47

    Cosmos

  • *****
  • Posts: 8,366
  • Joined: 04 Mar 2012
  • Loc: North Bay,Ontario,Canada

Posted 26 April 2021 - 07:25 PM

Thanks LDW47. I'm in the hobby as much out of technical interest in the capabilities of hobbyist instruments as I am for interest in the cosmos. But I think it's obvious I have little to gain from seeking B1 locations. First I need to learn to use what I have where I have it, then maybe I'll experiment with distance locations just to see how much difference it really makes. Meanwhile, it's cloudy tonight.

Wise thoughts, Bortle 2 is no slouch.



#17 MEE

MEE

    Messenger

  • -----
  • Posts: 497
  • Joined: 10 Jul 2010

Posted 26 April 2021 - 10:33 PM

In my opinion, a location with no or minimal light pollution is still Bortle Class 2 on an average night. It’s only class 1 if the transparency is good enough.

 

Your Bortle 2 location is good for regular observations  (assuming you are actually seeing Bortle 2 characteristics in your sky, and not basing that rating on your color zone) 

 

But you’ll never know how dark the other location will be unless you give it a try at least once. I’d suggest picking a night in which the transparency is forecast to be above average.

 

see this thread on the topic: https://www.cloudyni...a-bortle-1-sky/

see especially:

 

my post on the thread (#18) - mainly because it contains links and quotes from other discussions 

 

post #42- from BrooksObs - he knows a thing or two about the subject....

 

post #55 by Starman1: he has a lot of dark sky experience 


Edited by MEE, 26 April 2021 - 10:34 PM.

  • RLK1 likes this

#18 RLK1

RLK1

    Apollo

  • -----
  • Posts: 1,115
  • Joined: 19 Apr 2020

Posted 26 April 2021 - 11:42 PM

In my opinion, a location with no or minimal light pollution is still Bortle Class 2 on an average night. It’s only class 1 if the transparency is good enough.

 

Your Bortle 2 location is good for regular observations  (assuming you are actually seeing Bortle 2 characteristics in your sky, and not basing that rating on your color zone) 

 

But you’ll never know how dark the other location will be unless you give it a try at least once. I’d suggest picking a night in which the transparency is forecast to be above average.

 

see this thread on the topic: https://www.cloudyni...a-bortle-1-sky/

see especially:

 

my post on the thread (#18) - mainly because it contains links and quotes from other discussions 

 

post #42- from BrooksObs - he knows a thing or two about the subject....

 

post #55 by Starman1: he has a lot of dark sky experience 

Thanks for posting the link. I noted this excerpt from BrooksObs, "The familiar constellations fade into a sea of stars and the seemingly rather dramatic difference between levels of magnitude one is used to appear to diminish to the point that there seems little difference between them. The entire magnitude system seemingly becomes decidedly compressed to form an almost endless carpet of near equal stars."

And from another observer, post #30: "Getting Lost?  Some say they don't get lost under teaming dark skies.  Others say they are disoriented and have a harder time picking out constellations primary stars and asterisms.  I'm in this second camp.  It takes me one or two nights to adjust and get my bearings when moving from months of suburban star gazing where major constellation stars make up the majority of what's visible to skies filled with 100x+ more stars naked eye visible.  I kind of like the disorientation - it's like going to a different planet." 

The above matches my memory of what one would refer to as a bortle 1 sky...



#19 LDW47

LDW47

    Cosmos

  • *****
  • Posts: 8,366
  • Joined: 04 Mar 2012
  • Loc: North Bay,Ontario,Canada

Posted 27 April 2021 - 08:38 AM

Here is a taste of Bortle 1 through my simple p & s cam, not the best but a taste !

 

00EC978E-E482-432C-9A2F-E1B40580AA75.jpeg

7DEC6169-D3F6-4CFF-ADB6-507AE891307A.jpeg


  • Traveler likes this

#20 MarMax

MarMax

    Apollo

  • *****
  • Posts: 1,107
  • Joined: 27 May 2020
  • Loc: Los Angeles

Posted 27 April 2021 - 08:49 PM

Whether it's B1 or B2 I'm always overloaded with the sea of stars at my favorite dark site. I've only been there twice and the second time was more overload than the first. I would just sit in my folding chair, reclined back and looking up in amazement. No binoculars needed, just complete naked eye information overload. I'll have to do some better planning for trip #3.


  • LDW47 likes this

#21 Tony Flanders

Tony Flanders

    Hubble

  • *****
  • Posts: 19,673
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 28 April 2021 - 06:21 AM

I suppose I am very fortunate to be in a location described as Bortle class 2, in the California Northern Sierra Mountains. I'm a newbie with a 12" Dobson. I would not have to drive far to get to campgrounds shown as Bortle 1 on the maps. Not that I'm dissatisfied with the good seeing I have at home, but just wondering from a technical standpoint, would I see a noticeable difference in a Bortle 1 location?


I assume that when you say your location is "described as Bortle Class 2," you are deriving that from some map. Is that true? Note that the Bortle classes predicted by maps do not and cannot reflect situations on the ground perfectly. The maps do have some relationship to reality, but based on the maps all you can say with reasonable certainty is that an experienced observer on a night of typical good transparency would probably rate your sky somewhere between Bortle 1 and Bortle 3.

In any case, very few things in nature go in steps. If you're using one of the maps that show zones in different colors, you will not experience a sudden change in sky conditions when you drive over the boundary between two different colors! Since all Bortle 1 and 2 sites are necessarily quite distant from major sources of artificial light, it's very unusual for a short journey in a dark-sky part of the world to make a major difference. But there are three cases where it might:

1. If there is a small but intense light source in an otherwise dark area, a short trip away from that source could make a major difference.
2. If you are traveling from low altitude to high altitude, that could make a major difference.
3. If you are traveling from one side of a mountain range to another, the mountain range may serve as a natural barrier to artificial skyglow.


  • LDW47 and Augustus like this

#22 LDW47

LDW47

    Cosmos

  • *****
  • Posts: 8,366
  • Joined: 04 Mar 2012
  • Loc: North Bay,Ontario,Canada

Posted 28 April 2021 - 02:26 PM

I assume that when you say your location is "described as Bortle Class 2," you are deriving that from some map. Is that true? Note that the Bortle classes predicted by maps do not and cannot reflect situations on the ground perfectly. The maps do have some relationship to reality, but based on the maps all you can say with reasonable certainty is that an experienced observer on a night of typical good transparency would probably rate your sky somewhere between Bortle 1 and Bortle 3.

In any case, very few things in nature go in steps. If you're using one of the maps that show zones in different colors, you will not experience a sudden change in sky conditions when you drive over the boundary between two different colors! Since all Bortle 1 and 2 sites are necessarily quite distant from major sources of artificial light, it's very unusual for a short journey in a dark-sky part of the world to make a major difference. But there are three cases where it might:

1. If there is a small but intense light source in an otherwise dark area, a short trip away from that source could make a major difference.
2. If you are traveling from low altitude to high altitude, that could make a major difference.
3. If you are traveling from one side of a mountain range to another, the mountain range may serve as a natural barrier to artificial skyglow.

You sound good and as well a newcomer has to start somewhere in their thoughts, their questions ! That and other concerns that come to mind as part of their learning process and then experience first hand evidence hand in hand with what they are told. Its not an easy thing to be told the difference between this and that, in the end its the actual on the ground seeing / noticing that will do it for their eyes over many trys and maybe the fun of learning the workings of an  SQM-L meter for what it is worth, another good but variable tool.  PS: You are correct that on any given nite it is hard to distinguish the boundaries between this Bortle and that Bortle. 



#23 viewer

viewer

    Apollo

  • -----
  • Posts: 1,138
  • Joined: 06 Jan 2017
  • Loc: 60N, Helsinki, Finland

Posted 28 April 2021 - 05:38 PM

Do you think we have a tendency to wish we have better Bortles than we have? I went for a long time with 8, even if it may as well be a 9. My dark site is a 4, but somehow I want to emphasize it's not far from the border of 3, which is a bit out at sea. Thinking we are better off than we are grin.gif



#24 Tony Flanders

Tony Flanders

    Hubble

  • *****
  • Posts: 19,673
  • Joined: 18 May 2006
  • Loc: Cambridge, MA, USA

Posted 29 April 2021 - 06:17 AM

Do you think we have a tendency to wish we have better Bortles than we have?

Well, of course. The backyard of my country home, which is where I do most of my observing since I retired, is Bortle 4. Which is great compared to a typical suburb but truly pathetic compared to a genuinely dark site. The Milky Way is seriously washed out across the entire sky, and awful within 20 degrees of the horizon. When using a telescope, galaxy details that would pop out instantly under dark skies require a struggle. And there's a whole tier of detail that I simply can't see.

Sadly, it's a multi-hour drive to get to decent skies (Bortle 1 or 2). And that's not very attractive when I have Bortle 4 a 1-minute walk away.



#25 viewer

viewer

    Apollo

  • -----
  • Posts: 1,138
  • Joined: 06 Jan 2017
  • Loc: 60N, Helsinki, Finland

Posted 29 April 2021 - 09:31 AM

Ok, is the consensus Bortle 2 is practically the same as Bortle 1, if you don't look at the horizon? Could take a trip to the northernmost Lapland, after carefully checking the weather reports and of course the moon(less) situation in autumn. Then the northern lights could be a possible bonus, naturally "destroying" the starry sky. But if not hunting for the 1, being content with 2, there are many more options where to stay. Would you take 2?




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics