AFOV vs Aperture Poll

Hello, David,
I agree with what you say here. Many report that galaxies show more structure or detail at high powers.
Certain galaxy groupings are intrinsically interesting to me because they are groupings. The "trio in Leo" (M65,
66, and 3628), and Stephan's Quintet, come to mind. The trio is bright. I've only seen the Quintet once or twice and
I remember it as quite faint.
A galaxy like NGC 1275, which is such a strong radio source, interests me intrinsically because of that fact. I
tend to like galaxies to have something special about them if I am going to take the trouble to track them down.
I've never seen the Perseus Galaxy Cluster but would love to see it someday. To me it is intrinsically
interesting because it is a huge cluster of galaxies, at the mind-boggling distance of 300 million light years.
I agree also that for most faint galaxies, a wide apparent field of view is not essential.
Clear skies,
Bill Meyers

David Knisely wrote:

Hi there Bill. You posted:

And which is exactly how much fainter galaxies show up in very large telescopes. You have put your finger on a
much broader issue: "detect" is the right word, and the question in my mind is, why "detect" a long series of
objects with averted vision, unless a particular object is intrinsically interesting( (for example, the
Sagittarius dwarf, or a quasar) beyond the many many many similar objects in its class? Is it the thrill of
the hunt that drives people through the Herschel II list?

It can be, but there are many objects on these lists which do show detail at
higher power, so they do not necessarily require a wide-field eyepice to view
(although again, it can be helpful to use one). Some of the finer galaxy
groupings and the larger clusters are almost invisible at lower powers, but
can be quite interesting at high magnifications. I recall viewing the Perseus
galaxy cluster in a 20 inch at about 181x, and the galaxies outnumbered the
stars in the field! Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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(Tony Flanders) wrote in message m...

* An 8-inch scope with a full set of 80-degree-AFOV EPs.
* A 10-inch scope with a full set of 50-degree-AFOV EPs.

I find 80 dFOV EPs basically manditory at the lowest end
of the magnification range. The field is darker than a
55mm Plossl or a 68 dFOV Pan. At the other end FOV is not
that important, because if you need more, you can drop down
in magnification. So, with this caveat:

The 10-inch scope wins as long as the 50 dFOV EP set goes
down to 55mm Plossls.

(Tony Flanders) wrote in message m...

* An 8-inch scope with a full set of 80-degree-AFOV EPs.
* A 10-inch scope with a full set of 50-degree-AFOV EPs.

I find 80 dFOV EPs basically manditory at the lowest end
of the magnification range. The field is darker than a
55mm Plossl or a 68 dFOV Pan. At the other end FOV is not
that important, because if you need more, you can drop down
in magnification. So, with this caveat:

The 10-inch scope wins as long as the 50 dFOV EP set goes
down to 55mm Plossls.

I'll
take the aperture any day of the week and twice on Sunday. I remember when
my kellner with a 40 degree field was a big step up. I can live with 50
degree fields and deeper limiting magnitude.

I agree. I think it's an easy choice, 10 inches aperture and 50 degree AFOV
eyepieces (assuming good quality ones, such as TV plossls or Celestron Ultimas
or the like at the very least). Now if it were a choice between a 10 inch with
Ramsden or Huygens eyepieces, and an 8 inch with good quality 80 degree (or
even 50 degree) eyepieces, then I'd probably choose the 8 inch. 80 degrees is
great, but 50 degrees isn't bad, either.

I'll
take the aperture any day of the week and twice on Sunday. I remember when
my kellner with a 40 degree field was a big step up. I can live with 50
degree fields and deeper limiting magnitude.

I agree. I think it's an easy choice, 10 inches aperture and 50 degree AFOV
eyepieces (assuming good quality ones, such as TV plossls or Celestron Ultimas
or the like at the very least). Now if it were a choice between a 10 inch with
Ramsden or Huygens eyepieces, and an 8 inch with good quality 80 degree (or
even 50 degree) eyepieces, then I'd probably choose the 8 inch. 80 degrees is
great, but 50 degrees isn't bad, either.

On 12/30/03 11:56 +0900, Bill Meyers wrote:

Hello, Trane,

Hi, Bill.

Sorry to hear your skies are so light polluted. If you can get to a
dark sky, M5 and a number of the other bright Messier globulars can be
quite beautiful in a 4 inch at low power. I would say the same for M27,
which lies is a gorgeous Milky Way field.

Oh, I'm not complaining, really. In a cup-half-full sense, I
think that getting used to the current view of things can only
set me up to be truly blown away when I finally get an
opportunity to view under dark skies with large aperture. In the
meantime, I'll just continue enjoying what I can see. I enjoy
that very much.

Anyway, carry on with the poll comments. I don't have anything
intelligent to add there -- all I've ever used are
narrow(ish)-FOV EPs.

trane
--
//------------------------------------------------------------
// Trane Francks Tokyo, Japan
// Practice random kindness and senseless acts of beauty.

On 12/30/03 11:56 +0900, Bill Meyers wrote:

Hello, Trane,

Hi, Bill.

Sorry to hear your skies are so light polluted. If you can get to a
dark sky, M5 and a number of the other bright Messier globulars can be
quite beautiful in a 4 inch at low power. I would say the same for M27,
which lies is a gorgeous Milky Way field.

Oh, I'm not complaining, really. In a cup-half-full sense, I
think that getting used to the current view of things can only
set me up to be truly blown away when I finally get an
opportunity to view under dark skies with large aperture. In the
meantime, I'll just continue enjoying what I can see. I enjoy
that very much.

Anyway, carry on with the poll comments. I don't have anything
intelligent to add there -- all I've ever used are
narrow(ish)-FOV EPs.

trane
--
//------------------------------------------------------------
// Trane Francks Tokyo, Japan
// Practice random kindness and senseless acts of beauty.

c (Bill Ferris) wrote in message ...

Comparing the views in 10x50 binoculars used under pristine (22.0 MPSA) skies
against those in a 12-inch aperture under heavily light-polluted (18.0 MPSA)
skies, the binoculars are going to have a distinct advantage on nebulous
objects and objects large enough to require a wide field, low power view.

Yes without quibble or qualification w.r.t. large objects. As for nebulous
objects, the binoculars have an advantage *if* the objects are bright enough
to see at all *and* they are large enough to show significant structure at
10X. Frankly, that ends up being a pretty short list.

The
telescope's advantage would be limited to small, high surface brightness
objects.

Yes, in a sense. But remember that almost every galaxy has at its center
a small, high-surface brightness core. That is why a 12-inch scope under
18.0 MPSA skies can see *far* more galaxies than 10x50 binoculars under
22.0 MPSA skies. May not be much of a view, but detectable nonetheless.

Also, stars are by far the most numerous objects in the sky, and they are
*all* small and high in surface brightness! That includes some tens of
thousands of double stars that are unresolvable at 10X. And it includes
star clusters even when the cluster as a whole has low surface brightness.

Let's begin with the Messier catalog. Among the 110 objects are nine diffuse
nebulae and open clusters associated with nebulae: M1, M8, M16, M17, M20, M24,
M42, M43 and M78. All will appear larger and more contrasty in the 10x50
binoculars under true dark skies than in a 12-inch aperture under heavy light
pollution.

Sorry, I do not agree. I have in fact attempted all of the Messier objects
in 10x50 binoculars under pretty dark skies and in my 7-inch scope under
heavy light pollution, and my experience is at odds with your statement.
Granted, my fairly-dark site is probably closer to 21.0 MSPA than 22.0,
but I have also attempted most of the truly problematic Messier objects
with 10x50 binocular under pristine skies in California and Arizona.
And my own urban skies are probably closer to 17.0 MSPA than 18.0,
although I can't tell for sure until I have calibrated my readings.

M1 isn't much in either case, but I would have to give the nod to the
7-inch scope under bright skies; at least it shows a little structure,
and one quadrant is clearly darker than the rest. In 10x50 binoculars,
it is simply too small (and faint) to make much out.

M8 and M17 you could argue either way. On the whole, I would again
give the nod to the 7-inch scope; these both have very high surface
brightness as nebulae go, and both respond well to nebula filters.
On the other hand, they are also large enough to show good structure
even at a measly 10X.

M16 is simply different in the two cases. The scope shows the star
cluster better, and the binoculars show the nebulosity better.

M20 is definitely better in binoculars; the nebulosity is simply too
faint to see decently at my level of light pollution and at my
latitude. But I bet that in a southern-hemisphere city, the scope
would still win.

M24 is a clear win for the binoculars, due to its size.

I prefer the view of M42, M43 and M78 in the scope, and with M42, I
prefer it by a mile. No, ten miles. The scope under bright skies
doesn't show the subtle outlying nebulosity, but it does an infinitely
better job on the bright area around the Trapezium. This area alone
shows more detail in a decent scope from the city than the entire
nebula does in 10x50 binoculars under ideal circumstances.

All of this is in a 7-inch scope, mind you. A 12-inch would show
far more impressive views.

M31, M33 and M101 all would clearly be superior in the binoculars.

Agreed. And the Magellanic Clouds, and of course the Milky Way.
Maybe M81 and maybe NGC 253. And NGC 6822 if you can see it.
And that's the end of the list. All other galaxies are either
no worse in the scope or better.

And the low surface brightness Seyfert galaxy, M74, which would be
visible in the binoculars, may not be visible in the 12-inch.

Are you sure M74 is a Seyfert galaxy? Aren't you thinking of M77?
Seyfert galaxies have bright cores that stand up particularly well to
light pollution. As for M74, this is one of the few Messier objects
that still eludes me in 10x50 binoculars, even under pristine skies.
I have recorded one "maybe" sighting and a bunch of definite negatives.
In my 7-inch from the city, however, it is surprisingly easy -- nowhere
near as hard as M98, for instance. M74 *does* have a core with fairly
high surface brightness, albeit less prominent than many spiral galaxy's
cores. I betcha that in my 12-inch, I wouldn't even need averted vision.

M7, M41, M44 and M45) are 54' or larger in diameter...
The sky brightness in the 12-inch at such a low magnification
would be overwhelming. You'll see more stars in these four in
the binoculars.

Hunh? Surely you can't be serious! Granted, these clusters are
esthetically superior in binoculars regardless of sky brightness.
But see more stars? All I can say is: try it. Your statement
has no basis in reality; the scope shows every star visible in
binoculars without even trying, and thousands more.

There's no question but that a good pair of 10x50s under
pristine skies will show far more objects than a 12-inch
imprisoned by heavy light pollution.

Well, I suppose that it all depends what you count as an "object".
Also, how heavy is heavy light pollution? If you are talking about
broad daylight, I will agree with you. That is why I chose full
Moon as a widely-available reference point; I find an otherwise
dark sky at full Moon roughly equal to a mediocre suburban sky.
And I will say again that by any *reasonable* definition of
"object", a 12-inch scope at full Moon will show *far* more deep-
sky objects than 10x50 binoculars under pristine skies. At a
crude guess, ten times as many.

- Tony Flanders

c (Bill Ferris) wrote in message ...

Comparing the views in 10x50 binoculars used under pristine (22.0 MPSA) skies
against those in a 12-inch aperture under heavily light-polluted (18.0 MPSA)
skies, the binoculars are going to have a distinct advantage on nebulous
objects and objects large enough to require a wide field, low power view.

Yes without quibble or qualification w.r.t. large objects. As for nebulous
objects, the binoculars have an advantage *if* the objects are bright enough
to see at all *and* they are large enough to show significant structure at
10X. Frankly, that ends up being a pretty short list.

The
telescope's advantage would be limited to small, high surface brightness
objects.

Yes, in a sense. But remember that almost every galaxy has at its center
a small, high-surface brightness core. That is why a 12-inch scope under
18.0 MPSA skies can see *far* more galaxies than 10x50 binoculars under
22.0 MPSA skies. May not be much of a view, but detectable nonetheless.

Also, stars are by far the most numerous objects in the sky, and they are
*all* small and high in surface brightness! That includes some tens of
thousands of double stars that are unresolvable at 10X. And it includes
star clusters even when the cluster as a whole has low surface brightness.

Let's begin with the Messier catalog. Among the 110 objects are nine diffuse
nebulae and open clusters associated with nebulae: M1, M8, M16, M17, M20, M24,
M42, M43 and M78. All will appear larger and more contrasty in the 10x50
binoculars under true dark skies than in a 12-inch aperture under heavy light
pollution.

Sorry, I do not agree. I have in fact attempted all of the Messier objects
in 10x50 binoculars under pretty dark skies and in my 7-inch scope under
heavy light pollution, and my experience is at odds with your statement.
Granted, my fairly-dark site is probably closer to 21.0 MSPA than 22.0,
but I have also attempted most of the truly problematic Messier objects
with 10x50 binocular under pristine skies in California and Arizona.
And my own urban skies are probably closer to 17.0 MSPA than 18.0,
although I can't tell for sure until I have calibrated my readings.

M1 isn't much in either case, but I would have to give the nod to the
7-inch scope under bright skies; at least it shows a little structure,
and one quadrant is clearly darker than the rest. In 10x50 binoculars,
it is simply too small (and faint) to make much out.

M8 and M17 you could argue either way. On the whole, I would again
give the nod to the 7-inch scope; these both have very high surface
brightness as nebulae go, and both respond well to nebula filters.
On the other hand, they are also large enough to show good structure
even at a measly 10X.

M16 is simply different in the two cases. The scope shows the star
cluster better, and the binoculars show the nebulosity better.

M20 is definitely better in binoculars; the nebulosity is simply too
faint to see decently at my level of light pollution and at my
latitude. But I bet that in a southern-hemisphere city, the scope
would still win.

M24 is a clear win for the binoculars, due to its size.

I prefer the view of M42, M43 and M78 in the scope, and with M42, I
prefer it by a mile. No, ten miles. The scope under bright skies
doesn't show the subtle outlying nebulosity, but it does an infinitely
better job on the bright area around the Trapezium. This area alone
shows more detail in a decent scope from the city than the entire
nebula does in 10x50 binoculars under ideal circumstances.

All of this is in a 7-inch scope, mind you. A 12-inch would show
far more impressive views.

M31, M33 and M101 all would clearly be superior in the binoculars.

Agreed. And the Magellanic Clouds, and of course the Milky Way.
Maybe M81 and maybe NGC 253. And NGC 6822 if you can see it.
And that's the end of the list. All other galaxies are either
no worse in the scope or better.

And the low surface brightness Seyfert galaxy, M74, which would be
visible in the binoculars, may not be visible in the 12-inch.

Are you sure M74 is a Seyfert galaxy? Aren't you thinking of M77?
Seyfert galaxies have bright cores that stand up particularly well to
light pollution. As for M74, this is one of the few Messier objects
that still eludes me in 10x50 binoculars, even under pristine skies.
I have recorded one "maybe" sighting and a bunch of definite negatives.
In my 7-inch from the city, however, it is surprisingly easy -- nowhere
near as hard as M98, for instance. M74 *does* have a core with fairly
high surface brightness, albeit less prominent than many spiral galaxy's
cores. I betcha that in my 12-inch, I wouldn't even need averted vision.

M7, M41, M44 and M45) are 54' or larger in diameter...
The sky brightness in the 12-inch at such a low magnification
would be overwhelming. You'll see more stars in these four in
the binoculars.

Hunh? Surely you can't be serious! Granted, these clusters are
esthetically superior in binoculars regardless of sky brightness.
But see more stars? All I can say is: try it. Your statement
has no basis in reality; the scope shows every star visible in
binoculars without even trying, and thousands more.

There's no question but that a good pair of 10x50s under
pristine skies will show far more objects than a 12-inch
imprisoned by heavy light pollution.

Well, I suppose that it all depends what you count as an "object".
Also, how heavy is heavy light pollution? If you are talking about
broad daylight, I will agree with you. That is why I chose full
Moon as a widely-available reference point; I find an otherwise
dark sky at full Moon roughly equal to a mediocre suburban sky.
And I will say again that by any *reasonable* definition of
"object", a 12-inch scope at full Moon will show *far* more deep-
sky objects than 10x50 binoculars under pristine skies. At a
crude guess, ten times as many.

- Tony Flanders

c (Bill Ferris) wrote in message ...

The summer and winter
Milky Way are filled with many [large nebulous or pseudo-nebulous objects
and stellar associations] --not all of which have been catalogued or been
given cute common names--but all of which will be much more
detailed and interesting in the binoculars.

Having been so negative about the rest of your post, I must say that here
I agree 100%. It is precisely those objects -- many better even to the
naked eye than in binoculars -- that make me prefer 10x50 binoculars under
a dark sky to a 12-inch scope under full Moon. Oh yes, and don't forget
dark nebulae.

- Tony Flanders