Milky Way Magnitude?

Dear Astronomy Experts
Last night was the clearest in weeks. I even saw the band of stars
comprising the Milky Way, what is the magnitude when it is visible?
Cordially
G. Smith

"ypauls" skrev i melding ...
Last night was the clearest in weeks. I even saw the band of stars
comprising the Milky Way, what is the magnitude when it is visible?

The full moon is mag. -12.5, Sirius the brightest star in the night sky
mag. -1.5, whilst the faintest stars visible to the naked eye under good
conditions are around mag. +6.

"ypauls" skrev i melding ...
Last night was the clearest in weeks. I even saw the band of stars
comprising the Milky Way, what is the magnitude when it is visible?

The full moon is mag. -12.5, Sirius the brightest star in the night sky
mag. -1.5, whilst the faintest stars visible to the naked eye under good
conditions are around mag. +6.

G. Smith wrote:
Last night was the clearest in weeks. I even saw the band of stars
comprising the Milky Way, what is the magnitude when it is visible?

If you're talking about the classical band of milky light encompassing the
celestial sphere, it doesn't make much sense to talk about its integrated
magnitude since only half--at most--of the Milky Way is visible from any
location at any moment in time. Surface brightness is, however, another matter.

The Milky Way has a surface brightness similar to that of any other edge-on
disk galaxy in the sky. Let's take NGC 4565 for example. Its surface brightness
is 21.9 magnitude per square arcsecond. M31 isn't quite edge-on but it is a
grand spiral design, like our home galaxy. M31 has a surface brightness of 22.2
MPSA. The Milky Way is a highly structured object but, on the whole, I'd guess
it has a surface brightness of about 22.0 MPSA.

If you're asking about the brightness of the sky when the Milky Way becomes
visible, that depends on the transparency of the sky. I've seen the Milky Way
through Cassiopeia during a nearly full Moon when the sky surface brightness
would have been about 18.2 MPSA. However, that's from a high elevation site
with excellent transparency. The sky would have to be darker for the Milky Way
to be visible from a sea level site with lower transparency.

Regards,

Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
=============
Email: Remove "ic" from .comic above to respond

G. Smith wrote:
Last night was the clearest in weeks. I even saw the band of stars
comprising the Milky Way, what is the magnitude when it is visible?

If you're talking about the classical band of milky light encompassing the
celestial sphere, it doesn't make much sense to talk about its integrated
magnitude since only half--at most--of the Milky Way is visible from any
location at any moment in time. Surface brightness is, however, another matter.

The Milky Way has a surface brightness similar to that of any other edge-on
disk galaxy in the sky. Let's take NGC 4565 for example. Its surface brightness
is 21.9 magnitude per square arcsecond. M31 isn't quite edge-on but it is a
grand spiral design, like our home galaxy. M31 has a surface brightness of 22.2
MPSA. The Milky Way is a highly structured object but, on the whole, I'd guess
it has a surface brightness of about 22.0 MPSA.

If you're asking about the brightness of the sky when the Milky Way becomes
visible, that depends on the transparency of the sky. I've seen the Milky Way
through Cassiopeia during a nearly full Moon when the sky surface brightness
would have been about 18.2 MPSA. However, that's from a high elevation site
with excellent transparency. The sky would have to be darker for the Milky Way
to be visible from a sea level site with lower transparency.

Regards,

Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
=============
Email: Remove "ic" from .comic above to respond

All I want to know is:
If I can see the Milky Way band, am I looking at mag. 6 or mag. 3 or?
(It was a moonless night last night in Central California...)

"Bill Ferris" wrote in message
...
G. Smith wrote:
Last night was the clearest in weeks. I even saw the band of stars
comprising the Milky Way, what is the magnitude when it is visible?

If you're talking about the classical band of milky light encompassing
the
celestial sphere, it doesn't make much sense to talk about its
integrated
magnitude since only half--at most--of the Milky Way is visible from any
location at any moment in time. Surface brightness is, however, another
matter.

The Milky Way has a surface brightness similar to that of any other
edge-on
disk galaxy in the sky. Let's take NGC 4565 for example. Its surface
brightness
is 21.9 magnitude per square arcsecond. M31 isn't quite edge-on but it
is a
grand spiral design, like our home galaxy. M31 has a surface brightness
of 22.2
MPSA. The Milky Way is a highly structured object but, on the whole, I'd
guess
it has a surface brightness of about 22.0 MPSA.

If you're asking about the brightness of the sky when the Milky Way
becomes
visible, that depends on the transparency of the sky. I've seen the
Milky Way
through Cassiopeia during a nearly full Moon when the sky surface
brightness
would have been about 18.2 MPSA. However, that's from a high elevation
site
with excellent transparency. The sky would have to be darker for the
Milky Way
to be visible from a sea level site with lower transparency.

Regards,

Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
=============
Email: Remove "ic" from .comic above to respond

All I want to know is:
If I can see the Milky Way band, am I looking at mag. 6 or mag. 3 or?
(It was a moonless night last night in Central California...)

"Bill Ferris" wrote in message
...
G. Smith wrote:
Last night was the clearest in weeks. I even saw the band of stars
comprising the Milky Way, what is the magnitude when it is visible?

If you're talking about the classical band of milky light encompassing
the
celestial sphere, it doesn't make much sense to talk about its
integrated
magnitude since only half--at most--of the Milky Way is visible from any
location at any moment in time. Surface brightness is, however, another
matter.

The Milky Way has a surface brightness similar to that of any other
edge-on
disk galaxy in the sky. Let's take NGC 4565 for example. Its surface
brightness
is 21.9 magnitude per square arcsecond. M31 isn't quite edge-on but it
is a
grand spiral design, like our home galaxy. M31 has a surface brightness
of 22.2
MPSA. The Milky Way is a highly structured object but, on the whole, I'd
guess
it has a surface brightness of about 22.0 MPSA.

If you're asking about the brightness of the sky when the Milky Way
becomes
visible, that depends on the transparency of the sky. I've seen the
Milky Way
through Cassiopeia during a nearly full Moon when the sky surface
brightness
would have been about 18.2 MPSA. However, that's from a high elevation
site
with excellent transparency. The sky would have to be darker for the
Milky Way
to be visible from a sea level site with lower transparency.

Regards,

Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
=============
Email: Remove "ic" from .comic above to respond

You asked:

All I want to know is:
If I can see the Milky Way band, am I looking at mag. 6 or mag. 3 or?
(It was a moonless night last night in Central California...)

I think I know what you're after. At my home in Lake Stevens, Washington,
the Milky Way is fairly bright when my overall naked eye limiting magnitude
(NELM) is 5+. However, to my eyes, it is certainly visible when then NELM
is around 4.5. I would say, therefore, that the overall visual magnitude of
the Milky Way is around 4.5. Is this kind of what you want? It may not be
precise, as I am figuring this with recollection only in the middle of the
afternoon, but it is approximate and should give you a way to figure it out
more precisely for your eyes.

Martin

You asked:

All I want to know is:
If I can see the Milky Way band, am I looking at mag. 6 or mag. 3 or?
(It was a moonless night last night in Central California...)

I think I know what you're after. At my home in Lake Stevens, Washington,
the Milky Way is fairly bright when my overall naked eye limiting magnitude
(NELM) is 5+. However, to my eyes, it is certainly visible when then NELM
is around 4.5. I would say, therefore, that the overall visual magnitude of
the Milky Way is around 4.5. Is this kind of what you want? It may not be
precise, as I am figuring this with recollection only in the middle of the
afternoon, but it is approximate and should give you a way to figure it out
more precisely for your eyes.

Martin

(Paul Schlyter) wrote in message ...
In article , ypauls wrote:

If I can see the Milky Way band, am I looking at mag. 6 or mag. 3 or?

The sky is about mag 5 from my home. I can usually see the summer
Milky Way (Sagittarius/Cygnus) with moderately hazy skies, though not
at all on the worst dust-from-Sahara or volcanic-ash-from-Montserrat
nights.

I can occasionally glimpse the Milky Way through Cassiopeia on a
transparent winter night, but i can rarely see it through the Orion
region.

Perhaps the best way to estimate your limiting magnitude, however, is
to identify the dimmest star you can see, and look up its magnitude.
And remember that limiting magnitude is a subjective measure.

Clear skies!

--
------------------- Richard Callwood III --------------------
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~ eastern Massachusetts ~ USDA zone 6 (1992-95) ~
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