Magnitude question

Përhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about it.
With cartes du ciel i can see what stars and planets there are and when and
when i look at the information of the stars i get the magnitude. I know that
it has something to do with the strength of the light. My question is: witch
value do i need to see a star? I'd love to know it because otherwise i don't
know if the star if visible for the eye or not.

Passero wrote:

Përhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about it.
With cartes du ciel i can see what stars and planets there are and when and
when i look at the information of the stars i get the magnitude. I know that
it has something to do with the strength of the light. My question is: witch
value do i need to see a star? I'd love to know it because otherwise i don't
know if the star if visible for the eye or not.

See: http://liftoff.msfc.nasa.gov/academy/universe/mag.html

Passero wrote:

Përhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about it.
With cartes du ciel i can see what stars and planets there are and when and
when i look at the information of the stars i get the magnitude. I know that
it has something to do with the strength of the light. My question is: witch
value do i need to see a star? I'd love to know it because otherwise i don't
know if the star if visible for the eye or not.

See: http://liftoff.msfc.nasa.gov/academy/universe/mag.html

Passero wrote:

Përhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about it.
With cartes du ciel i can see what stars and planets there are and when and
when i look at the information of the stars i get the magnitude. I know that
it has something to do with the strength of the light. My question is: witch
value do i need to see a star? I'd love to know it because otherwise i don't
know if the star if visible for the eye or not.

See: http://liftoff.msfc.nasa.gov/academy/universe/mag.html

Passero wrote:
Perhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about it.
With cartes du ciel i can see what stars and planets there are and when and
when i look at the information of the stars i get the magnitude. I know that
it has something to do with the strength of the light. My question is: witch
value do i need to see a star? I'd love to know it because otherwise i don't
know if the star if visible for the eye or not.

The magnitude of a star is indeed an expression of its brightness. The
magnitude system is "backwards": brighter stars have lower magnitudes.
Thus, for example, the brightest star in the night sky, Sirius, has
magnitude about -1.4, whereas the dimmest star typically visible from a
dark sky site (by the unaided eye) is generally about magnitude 6 or so.
This limit isn't exact because eyes, sites, and conditions all vary quite
substantially. Nonetheless, you will occasionally hear people talk about
"a magnitude 5.7 location," or something similar. That means that the
dimmest star visible by that observer at that location is magnitude 5.7.
Under those conditions, one might be able to see about 2,000 stars at any
time of darkness.

A telescope will increase the magnitude limit--the dimmest star one can
see. The larger the telescope, the dimmer a star that one can see. A
typical formula for the increase is

M - m = 5 (log A - log a)

where

M = limiting magnitude through the telescope
m = limiting magnitude with the unaided eye

A = aperture of the telescope
a = aperture of the eye (that is, the size of your pupil)

However, as with many such formulae, it simplifies many aspects of using
telescopes to observe. I wouldn't omit an observing target just because
the formula says it's too dim, nor would I necessarily expect to see it
just because the formula says it's bright enough. In particular, nebulae
and galaxies--extended objects like those--won't be nearly as easy to see
as a star of the same magnitude, because the light of a nebula or galaxy
is spread out and therefore harder to see.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Passero wrote:
Perhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about it.
With cartes du ciel i can see what stars and planets there are and when and
when i look at the information of the stars i get the magnitude. I know that
it has something to do with the strength of the light. My question is: witch
value do i need to see a star? I'd love to know it because otherwise i don't
know if the star if visible for the eye or not.

The magnitude of a star is indeed an expression of its brightness. The
magnitude system is "backwards": brighter stars have lower magnitudes.
Thus, for example, the brightest star in the night sky, Sirius, has
magnitude about -1.4, whereas the dimmest star typically visible from a
dark sky site (by the unaided eye) is generally about magnitude 6 or so.
This limit isn't exact because eyes, sites, and conditions all vary quite
substantially. Nonetheless, you will occasionally hear people talk about
"a magnitude 5.7 location," or something similar. That means that the
dimmest star visible by that observer at that location is magnitude 5.7.
Under those conditions, one might be able to see about 2,000 stars at any
time of darkness.

A telescope will increase the magnitude limit--the dimmest star one can
see. The larger the telescope, the dimmer a star that one can see. A
typical formula for the increase is

M - m = 5 (log A - log a)

where

M = limiting magnitude through the telescope
m = limiting magnitude with the unaided eye

A = aperture of the telescope
a = aperture of the eye (that is, the size of your pupil)

However, as with many such formulae, it simplifies many aspects of using
telescopes to observe. I wouldn't omit an observing target just because
the formula says it's too dim, nor would I necessarily expect to see it
just because the formula says it's bright enough. In particular, nebulae
and galaxies--extended objects like those--won't be nearly as easy to see
as a star of the same magnitude, because the light of a nebula or galaxy
is spread out and therefore harder to see.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Passero wrote:
Perhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about it.
With cartes du ciel i can see what stars and planets there are and when and
when i look at the information of the stars i get the magnitude. I know that
it has something to do with the strength of the light. My question is: witch
value do i need to see a star? I'd love to know it because otherwise i don't
know if the star if visible for the eye or not.

The magnitude of a star is indeed an expression of its brightness. The
magnitude system is "backwards": brighter stars have lower magnitudes.
Thus, for example, the brightest star in the night sky, Sirius, has
magnitude about -1.4, whereas the dimmest star typically visible from a
dark sky site (by the unaided eye) is generally about magnitude 6 or so.
This limit isn't exact because eyes, sites, and conditions all vary quite
substantially. Nonetheless, you will occasionally hear people talk about
"a magnitude 5.7 location," or something similar. That means that the
dimmest star visible by that observer at that location is magnitude 5.7.
Under those conditions, one might be able to see about 2,000 stars at any
time of darkness.

A telescope will increase the magnitude limit--the dimmest star one can
see. The larger the telescope, the dimmer a star that one can see. A
typical formula for the increase is

M - m = 5 (log A - log a)

where

M = limiting magnitude through the telescope
m = limiting magnitude with the unaided eye

A = aperture of the telescope
a = aperture of the eye (that is, the size of your pupil)

However, as with many such formulae, it simplifies many aspects of using
telescopes to observe. I wouldn't omit an observing target just because
the formula says it's too dim, nor would I necessarily expect to see it
just because the formula says it's bright enough. In particular, nebulae
and galaxies--extended objects like those--won't be nearly as easy to see
as a star of the same magnitude, because the light of a nebula or galaxy
is spread out and therefore harder to see.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

It depends on how dark your skies are. Negative magnitudes are brighter than
zero magnitude which is brighter than positive magnitudes. Each magnitude is
about 2.5 times brighter than the previous.

How faint can you see? Take the chart and discover the magnitude of the
faintest stars you can see. That tells you the limiting magnitude for that
site. Away from the city it can be 6th magnitude or even fainter if you have
really dark skies. In the city it may be 5th, 4th or even 3rd magnitude is
the faintest you can see.

Clear Skies!

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
************************************************** **********


"Passero" wrote in message
...
Përhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about
it.
With cartes du ciel i can see what stars and planets there are and when
and
when i look at the information of the stars i get the magnitude. I know
that
it has something to do with the strength of the light. My question is:
witch
value do i need to see a star? I'd love to know it because otherwise i
don't
know if the star if visible for the eye or not.

It depends on how dark your skies are. Negative magnitudes are brighter than
zero magnitude which is brighter than positive magnitudes. Each magnitude is
about 2.5 times brighter than the previous.

How faint can you see? Take the chart and discover the magnitude of the
faintest stars you can see. That tells you the limiting magnitude for that
site. Away from the city it can be 6th magnitude or even fainter if you have
really dark skies. In the city it may be 5th, 4th or even 3rd magnitude is
the faintest you can see.

Clear Skies!

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
************************************************** **********


"Passero" wrote in message
...
Përhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about
it.
With cartes du ciel i can see what stars and planets there are and when
and
when i look at the information of the stars i get the magnitude. I know
that
it has something to do with the strength of the light. My question is:
witch
value do i need to see a star? I'd love to know it because otherwise i
don't
know if the star if visible for the eye or not.

It depends on how dark your skies are. Negative magnitudes are brighter than
zero magnitude which is brighter than positive magnitudes. Each magnitude is
about 2.5 times brighter than the previous.

How faint can you see? Take the chart and discover the magnitude of the
faintest stars you can see. That tells you the limiting magnitude for that
site. Away from the city it can be 6th magnitude or even fainter if you have
really dark skies. In the city it may be 5th, 4th or even 3rd magnitude is
the faintest you can see.

Clear Skies!

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
************************************************** **********


"Passero" wrote in message
...
Përhaps a stupid question for some people but i don't know a lot about
astronomy but i'm interessted in it so i would like to learn more about
it.
With cartes du ciel i can see what stars and planets there are and when
and
when i look at the information of the stars i get the magnitude. I know
that
it has something to do with the strength of the light. My question is:
witch
value do i need to see a star? I'd love to know it because otherwise i
don't
know if the star if visible for the eye or not.