Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
acey
member
Reged: 01/09/09
Posts: 39
|
|
What limiting magnitude is required in order that the Milky Way will be visible?
Obviously there are factors such as whether it's barely or clearly seen, how high it is in the sky, etc, but I'm interested in whatever estimates people can offer. My personal guess would be around 5.
|
JakeSaloranta
sage
Reged: 09/18/08
Posts: 229
Loc: Sisu, Sauna, Sibelius...
|
|
Depends on the Milky Way doesn't it. You want it to be from horizon to horizon or just when the brightest parts start to show up...
I'd say in order to "recognize" the MW from the sky you need:
Winter Milky Way (Auriga and below) requires ZLM 6+
Summer Milky Way (Cygnus/Cassiopeia-region) requires ZLM 5.5+
Sagittarius-Scorpius region is pretty much 5.0 or something. It is not visible from Finland so I cannot say much about it - at least from the 5.0 ZLM magnitude (I've never observed from such a horrible place)...
Also the Canis Major and below area is pretty bright Milky Way-wise but it too is invisible from Finland.
/Jake
|
gmazza
member
Reged: 03/10/09
Posts: 99
Loc: RS, Brazil, 29S 51W
|
|
I think at 4.5 it start to show little detail, with 5.5 could see it at full if no points of it are on light polution domes.
--------------------
Oberwerk Ultra 10X50
Garrett Signature 15X85
|
Tony Flanders
Post Laureate
Reged: 05/18/06
Posts: 3369
Loc: Cambridge, MA, USA
|
|
Quote:
What limiting magnitude is required in order that the Milky Way will be visible?
Obviously there are factors such as whether it's barely or clearly seen, how high it is in the sky, etc, but I'm interested in whatever estimates people can offer. My personal guess would be around 5.
The other variable is that people vary hugely in their ability to see faint stars. A sky that I call mag 5.5 another person might call mag 6.0, and yet another mag 5.0, or even worse.
But as for me, I am essentially unable to detect the Milky Way at my local urban park, ZLM around 4.7, SQM around 18.0 at best.
At my favorite inner-suburban site, ZLM around 5.1, SQM around 18.7, I can see the Cygnus Star Cloud when it's overhead, but it's awfully vague and unrewarding.
In the mid-suburbs, ZLM around 5.5, SQM around 19.5, I can see the overhead Milky Way quite clearly from Perseus through Cygnus, and I can trace it down all the way to the Great Sagittarius Star Cloud on a good night. The Milky Way is much brighter in Sagittarius than in Cygnus, but that's more than counterbalanced by the fact that the sky is much brighter 20 degrees off the horizon than overhead.
I can see parts of the winter Milky Way, from Perseus through Auriga and Gemini, from my club's site in the outer suburbs, ZLM around 5.7, SQM around 20.0.
--------------------
Tony Flanders
First and foremost observing love: naked eye.
Second, binoculars.
Last but not least, telescopes.
And I sometimes dabble with cameras.
|
NerfMonkey
sage
Reged: 06/12/08
Posts: 478
Loc: NE Ohio
|
|
I agree with Tony about differences among people's limiting magnitude measurements. There's a 0.8 magnitude difference from when I'm not wearing my glasses to when I am.
On the other hand, that's only because the stars tighten up and fainter ones become visible as a result of the sharper focus. The visibility of large diffuse objects like the Milky Way doesn't really seem to be affected. Other people's experiences may be different.
On a good night from my back yard in the red zone (Bortle class 6.5 and a limiting magnitude of about 5.3 for me) I can see the Cygnus star cloud and some extremely faint traces of the Milky Way extending to around Albireo. That's it.
From the site I use about 30 minutes away in the orange zone (Bortle class 5 or so with a limiting magnitude of about 6), the Milky Way is extremely obvious and stretches from Sagittarius near the southern horizon to the southern end of Cassiopeia; and the only reason it's not visible farther north is because of the light dome from Youngstown. M31, the Double Cluster, M7, M8, M24, Mel 111 and - I think - the North America Nebula are all clearly visible.
The Milky Way from this location is nothing like at an extremely dark site but it's still very easily visible, while at my suburban site with a NELM just 0.7 magnitudes lower it's hardly visible at all. I think for the Milky Way to be more than just a vague hint you need a NELM of close to 6, if you have perfect vision or are wearing glasses to correct it.
--------------------
Mike
Zhumell 12", Oberwerk 15x70s
107 Messiers, 247 total DSOs, 6 planets, 1 comet
|
AlanK
professor emeritus
Reged: 01/26/07
Posts: 510
Loc: Auckland, New Zealand
|
|
Also depends where you are. From my light polluted backyard in Auckland it is faintly visible even at ZNLM 4.0. The Saggitarius and Crux areas are among the brightest parts of it and both are very high in the New Zealand skies.
--------------------
Clear skies!
18 inch f4.5 Obsession #1637
12 inch f5.4 reflector
Just another frozen astronomer
Kumeu Observatory
Auckland NZ
7,276 deep sky objects incl 4,670 ngcs
Who dares - observes!
|
BillFerris
Carpal Tunnel
Reged: 07/17/04
Posts: 2900
|
|
On full Moon nights (sky surface brightness about 18.0 MPSAS), I've observed portions of the northern Milky Way. It's not too difficult from a site with excellent transparency.
Bill in Flag
--------------------
Grand Canyon Adventure
Lowering the Threshold
18" Obsession
4.5" Meade 4500
10x50 Swift Audubon
Cosmic Voyage
|
Ptarmigan
Carpal Tunnel
Reged: 09/23/04
Posts: 2305
Loc: Arctic
|
|
Depends on the weather and seeing. If the humidity is low and seeing is great, you could see bits of the Milky Way. Also, if there is no Moon, that helps too.
--------------------
Ptarmigans=Cute and Cuddly
Meade Starfinder 8
Nikon 10x50
Rebel XT
|
FirstSight
Post Laureate
Reged: 12/26/05
Posts: 3796
Loc: Raleigh, NC
|
|
As I was reminded vividly on a recent trip to one of the relatively un-light polluted out-islands in the Bahamas, and comparing it to plainly being able to "see" the Milky Way from the beach in North Carolina -
There's an ENORMOUS difference between being able to easily, plainly see a mostly homogeneous-looking white stream of the Milky Way over roughly a 90 degree band from Sagittarius up through Cygnus (North Carolina beach site compromised by light pollution)
- versus being able to vividly see the detailed structure of the Milky Way from below Sagittarius, up through Cygnus, and continuing through Cassiopia - including well-defined individual dense strands and clouds of starlight clearly separated by well-defined dark streams and bands, especially between Ophiuchus and Sagittarius (very dark site on Bahamas out-island). There's quite a difference in what you see between partial mag 5.0 skies (mainly directly overhead and running down directly south) and mag 6-plus skies completely uncompromised by any light pollution in any direction.
I can only imagine it gets even better if you can see the Milky Way from a southerly location with a dry climate and a few thousand feet of altitude.
--------------------
Chris M., aka "First Sight"
Orion XT12i Dob with Moonlite CR-2 focuser
WO Megrez 90 refractor on UniStar Light mount
Nikon 10x50 Binoculars
|
Hrundi
Pooh-Bah
Reged: 02/06/08
Posts: 1165
Loc: Estonia
|
|
I've seen the cygnus stretch in mag 5 skies at ~30 degrees.
It's not particularly exciting though.
I'd say it's worth seeing at around zlm 6+.
--------------------
|
|
3 registered and 2 anonymous users are browsing this forum.
Moderator: Olivier Biot
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 359
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
