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• The light curve of C/2006 P1 (McNaught) is certainly intriguing. I can t envision it maintaining such a high n value. That being said, and I know this is a
Message 1 of 12 , Nov 1, 2006
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The light curve of C/2006 P1 (McNaught) is certainly intriguing. I
can't envision it maintaining such a high "n" value. That being said,
and I know this is a hypothetical question, but...

...if a comet is within 15, 10, or 5 degrees of the sun, respectively,
how bright would it have to be in order to be visible to the naked
eye, assuming decent sky transparency?

Clear Skies,
Phil
• ... Based on own my extensive experimentation, made during the early 1980 s, I can offer the following formula that generally predicts the daytime visibility
Message 1 of 12 , Nov 1, 2006
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--- In comets-ml@yahoogroups.com, "Phil" <pcreed4863@...> wrote:
>
> The light curve of C/2006 P1 (McNaught) is certainly intriguing. I
> can't envision it maintaining such a high "n" value. That being said,
> and I know this is a hypothetical question, but...
>
> ...if a comet is within 15, 10, or 5 degrees of the sun, respectively,
> how bright would it have to be in order to be visible to the naked
> eye, assuming decent sky transparency?
>

Based on own my extensive experimentation, made during the early
1980's, I can offer the following formula that generally predicts the
daytime visibility limits for Sungrazing comets using binoculars or a
small telescope. My orginal paper, addressing this subject in detail,
appeared in the ICQ many years ago. I don't off hand have the reference.

The formula below is accurate for an instrument of 8cm aperture using
20x, working with the Sun's disk obscured, and in very clear skies. The
formula is only meant to be valid within 20 degrees of the Sun. The
term "m" is the lower magnitude limit, while "E" is the object's solar
elongation in degrees.

m = -2.5 + 2 log E

Although it is difficult to say with any accuracy, I would anticipate
that nakedeye visibility would probably require the object to be
several magnitudes brighter than for an instrument of 8cm aperture.

I would also have to add that there is zero chance of C/2006P1 becoming
a nakedeye, daylight object.

JBortle
• Consider Venus, mag -4.3. Can you see Venus with the naked eye at 5 deg elongation? Certainly not while the Sun is up! 10deg? - yes, with Sun below horizon....
Message 1 of 12 , Nov 1, 2006
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Consider Venus, mag -4.3. Can you see Venus with the naked eye at 5 deg
elongation? Certainly not while the Sun is up! 10deg? - yes, with Sun below
horizon....

The other factor is how the light from the comet is distributed. Venus is (to
the naked eye) a point source. Spread the light over an area equivalent to the
size of the moon, and the surface brightness is _much_ less.

Dave Herald
Canberra, Australia

----- Original Message -----
From: "Phil" <pcreed4863@...>
To: <comets-ml@yahoogroups.com>
Sent: Thursday, November 02, 2006 1:43 AM
Subject: [comets-ml] Sungrazing comet visibility

The light curve of C/2006 P1 (McNaught) is certainly intriguing. I
can't envision it maintaining such a high "n" value. That being said,
and I know this is a hypothetical question, but...

...if a comet is within 15, 10, or 5 degrees of the sun, respectively,
how bright would it have to be in order to be visible to the naked
eye, assuming decent sky transparency?

Clear Skies,
Phil

Comet Observations List: http://groups.yahoo.com/group/CometObs/
Comet Images List: http://groups.yahoo.com/group/Comet-Images/

NOTICE: Material quoted or re-posted from the Comets Mailing List should be
indicated by:

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• ... With all respect John, Maybe not zero but less than 5% :). I always use David Levy s sequence that comets are like cats :) unpredict. I do not observe
Message 1 of 12 , Nov 1, 2006
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>I would also have to add that there is zero chance of C/2006P1 becoming
>a nakedeye, daylight object.

With all respect John,

Maybe not zero but less than 5% :). I always use David Levy's sequence
that comets are like cats :) unpredict.

I do not observe famous comet West but I readed some time ago Gary Kronk's
note that forecasts put comet at 5 mag. On other hand comet Kohoutek was put
at -8 or even -10 and what happend almost every from this list know.
That's what the comets are famous for me. You really never know....

Best regards,
Maciej
• ... deg ... Sun below ... Venus is (to ... equivalent to the ... An interesting point, also I think touched upon in my article, was how much more 18th and 19th
Message 1 of 12 , Nov 1, 2006
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--- In comets-ml@yahoogroups.com, "Dave Herald" <drherald@...> wrote:
>
> Consider Venus, mag -4.3. Can you see Venus with the naked eye at 5
deg
> elongation? Certainly not while the Sun is up! 10deg? - yes, with
Sun below
> horizon....
>
> The other factor is how the light from the comet is distributed.
Venus is (to
> the naked eye) a point source. Spread the light over an area
equivalent to the
> size of the moon, and the surface brightness is _much_ less.
>
> Dave Herald
> Canberra, Australia
>

An interesting point, also I think touched upon in my article, was
how much more 18th and 19th century astronomers could "see" when it
came to difficult objects, compared to what amateur's today accept
as "visible". It's indeed rather shocking.

As I recall, the great 19th Harvard astronomer G.P.Bond, states in
one of his books that the planet Venus is always visible to the
unaided eye in daylight at Cambridge (MA) providing its elongation
from the Sun is greater than 5 degrees. Near superior conjunction,
its magnitude would only be around -3.5 . Astonishing to most today,
perhaps, but true providing the sky is very clear. In fact, with
binoculars and using suitable cautions, Venus can be followed to
within just a dozen arc minutes of the solar limb!

In addition, the apparent telescopic size of the typical sungrazer's
visible head (as reported for say Ikeya-Seki and 1882II) shrinks to
about 0.2' around the time of perihelion passage. Thus, it looks
about the same size Venus does at superior conjunction. Needless to
say, the brightness of a sungrazer's head is extremely concentrated
near T, not at all spread out. Further, in the case of Comet West,
its head was also less than 1' in diameter when I saw it during the
daytime.

JBortle
• ... You are comparing apples and oranges. An observation like Bond s is an example of an extreme case: it s the answer to the question, can Venus be seen in
Message 1 of 12 , Nov 1, 2006
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cnj999 wrote:
> As I recall, the great 19th Harvard astronomer G.P.Bond, states in
> one of his books that the planet Venus is always visible to the
> unaided eye in daylight at Cambridge (MA) providing its elongation
> from the Sun is greater than 5 degrees. Near superior conjunction,
> its magnitude would only be around -3.5 . Astonishing to most today,
> perhaps, but true providing the sky is very clear. In fact, with
> binoculars and using suitable cautions, Venus can be followed to
> within just a dozen arc minutes of the solar limb!

You are comparing apples and oranges. An observation like Bond's is an
example of an extreme case: it's the answer to the question, "can Venus
be seen in daylight under the best possible conditions?"

On the other hand, you are comparing this extreme to "populist"
astronomy, which asks the very different question, "can a typical
backyard amateur expect to see Venus in daylight under typical conditions?"

I really don't see the point in comparing the two at all. And I know of
some amateurs here out west that regularly make the same sort of extreme
observations. Comparing to them would be something less curmudgeonly...

I for one am less shocked by Bond's assertion than by the
meaninglessness of such a poor comparison. ;-)

Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html
• ... in ... elongation ... conjunction, ... today, ... is an ... Venus ... conditions? ... know of ... extreme ... curmudgeonly... ... Extreme? By no means.
Message 1 of 12 , Nov 1, 2006
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--- In comets-ml@yahoogroups.com, Greg Crinklaw <crinklaw@...> wrote:
>
> cnj999 wrote:
> > As I recall, the great 19th Harvard astronomer G.P.Bond, states
in
> > one of his books that the planet Venus is always visible to the
> > unaided eye in daylight at Cambridge (MA) providing its
elongation
> > from the Sun is greater than 5 degrees. Near superior
conjunction,
> > its magnitude would only be around -3.5 . Astonishing to most
today,
> > perhaps, but true providing the sky is very clear. In fact, with
> > binoculars and using suitable cautions, Venus can be followed to
> > within just a dozen arc minutes of the solar limb!
>
> You are comparing apples and oranges. An observation like Bond's
is an
> example of an extreme case: it's the answer to the question, "can
Venus
> be seen in daylight under the best possible conditions?"
>
> On the other hand, you are comparing this extreme to "populist"
> astronomy, which asks the very different question, "can a typical
> backyard amateur expect to see Venus in daylight under typical
conditions?"
>
> I really don't see the point in comparing the two at all. And I
know of
> some amateurs here out west that regularly make the same sort of
extreme
> observations. Comparing to them would be something less
curmudgeonly...
>
> I for one am less shocked by Bond's assertion than by the
> meaninglessness of such a poor comparison. ;-)
>

Extreme? By no means. Bond's comment is typical of hundreds of such
entries to be found. If you look through the literature you will find
that so-called extreme observations were utterly commonplace during
the 19th and made by observers of every kind. However, once
photography took astronomy by storm, the techniques and effort
neccessary to conduct such observations. They became considered
extreme observation in the 20th century only out of ignorance and the
myth that such thing couldn't be done. The appearance of Comet Ikeya-
Seki in 1965 changed that and for a time resulted in a rebirth of
near-Sun observation, particularly with regard to comets.
Unfortunately, for most observers today, this sort of observation has
once again become a lost art.

The observation of objects in very close proximity to the solar disk
can be accomplished by any average observer if they only bother to
learn how to safely go about it. I used to demonstrate how easy it
was in conjunction with my comet lectures years ago. Following the
presentation, to their astronishment, I would have audience members,
weather permitting, safely go outside and be able to picking out
Venus at very smaller elongations. Although few observers seem able
to do it currently, it really is only a matter of having the
observing knowledge, nothing exceptional is involved...even you might
be able to learn to do it! ;)

JBortle
• ... I m sorry: you didn t understand what I said. But I m not going to argue about it. -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New
Message 1 of 12 , Nov 1, 2006
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cnj999 wrote:
> Extreme? By no means.

I'm sorry: you didn't understand what I said. But I'm not going to

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html
• John, I am not that familiar with the specific observations of astronomers in prior centuries, but I may have a theory... ...that it WAS indeed much clearer.
Message 1 of 12 , Nov 1, 2006
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John,

I am not that familiar with the specific observations of astronomers
in prior centuries, but I may have a theory...

...that it WAS indeed much clearer.

Pollution is a significant visual impediment. Until I did a project
for my local astronomy club, I didn't realize exactly how MUCH.

In the Eastern U.S., summertime visibility typically runs 25-30 miles.
This doesn't sound too bad until you realize that under natural
conditions, the visibility SHOULD be 90 miles. The latter figure is
comparable to typical visibility in the Desert Southwest!

Most of the visibility impairment in the Eastern U.S. is attributable
to sulfur dioxide emissions from older coal-fired power plants. (By
2010, SO2 concentrations in the Eastern U.S. should start to fall
sharply with the implementation of the Clean Air Interstate Rule)
Sulfate particles in humid environments grow to sizes that are
INSIDIOUSLY effective at scattering light, thus those hot, humid,
"air-that-you-can-wear" days are the haziest. A warm, humid
environment DOES NOT mean it should naturally be hazy. Otherwise,
Hawaii would have chronically-low visibility. For more on visibility
in the Eastern U.S., the VIEWS website is the best one I could find:

http://vista.cira.colostate.edu/views/

The sections on "spatial patterns" and "composition" for the Eastern
U.S. are most revealing. Let's just say the combined with the
cloudiness, light pollution, and haze, we Ohio stargazers aren't
exactly God's chosen people when it comes to our hobby.

More on pollution's effect on visibility can be found here:

http://www.epa.gov/oar/visibility/what.html

tangential to the subject at-hand, but the point is, the 18th and
early-19th centuries had a mere fraction of the pollution sources that
we have today. Based on what I researched for my astronomy club's
presentation, my assertion would be that the sky on a humid, 90-degree
day in an Eastern U.S. location in the early 1800s would look by
today's standards as if a master-blaster cold front had just come through.

Clear Skies to all,
Phillip J. Creed

--- In comets-ml@yahoogroups.com, "cnj999" <jbortle@...> wrote:
>
> An interesting point, also I think touched upon in my article, was
> how much more 18th and 19th century astronomers could "see" when it
> came to difficult objects, compared to what amateur's today accept
> as "visible". It's indeed rather shocking.
>
> As I recall, the great 19th Harvard astronomer G.P.Bond, states in
> one of his books that the planet Venus is always visible to the
> unaided eye in daylight at Cambridge (MA) providing its elongation
> from the Sun is greater than 5 degrees. Near superior conjunction,
> its magnitude would only be around -3.5 . Astonishing to most today,
> perhaps, but true providing the sky is very clear. In fact, with
> binoculars and using suitable cautions, Venus can be followed to
> within just a dozen arc minutes of the solar limb!
>
> JBortle
>
• There was a recent discovery channel show which said sunlight to the ground has gone down 25% since the 1920 s all over the earth due to pollution. So it would
Message 1 of 12 , Nov 1, 2006
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There was a recent discovery channel show which said sunlight to the
ground has gone down 25% since the 1920's all over the earth due to
pollution.
So it would have decreased the view up by the same amount.

On Wed, 1 Nov 2006 2:26 pm, Phil wrote:
> John,
>
> I am not that familiar with the specific observations of astronomers
> in prior centuries, but I may have a theory...
>
> ...that it WAS indeed much clearer.
>
> Pollution is a significant visual impediment. Until I did a project
> for my local astronomy club, I didn't realize exactly how MUCH.
>
> In the Eastern U.S., summertime visibility typically runs 25-30 miles.
> This doesn't sound too bad until you realize that under natural
> conditions, the visibility SHOULD be 90 miles. The latter figure is
> comparable to typical visibility in the Desert Southwest!
>
> Most of the visibility impairment in the Eastern U.S. is attributable
> to sulfur dioxide emissions from older coal-fired power plants. (By
> 2010, SO2 concentrations in the Eastern U.S. should start to fall
> sharply with the implementation of the Clean Air Interstate Rule)
> Sulfate particles in humid environments grow to sizes that are
> INSIDIOUSLY effective at scattering light, thus those hot, humid,
> "air-that-you-can-wear" days are the haziest. A warm, humid
> environment DOES NOT mean it should naturally be hazy. Otherwise,
> Hawaii would have chronically-low visibility. For more on visibility
> in the Eastern U.S., the VIEWS website is the best one I could find:
>
> http://vista.cira.colostate.edu/views/
>
> The sections on "spatial patterns" and "composition" for the Eastern
> U.S. are most revealing. Let's just say the combined with the
> cloudiness, light pollution, and haze, we Ohio stargazers aren't
> exactly God's chosen people when it comes to our hobby.
>
> More on pollution's effect on visibility can be found here:
>
> http://www.epa.gov/oar/visibility/what.html
>
> tangential to the subject at-hand, but the point is, the 18th and
> early-19th centuries had a mere fraction of the pollution sources that
> we have today. Based on what I researched for my astronomy club's
> presentation, my assertion would be that the sky on a humid, 90-degree
> day in an Eastern U.S. location in the early 1800s would look by
> today's standards as if a master-blaster cold front had just come
> through.
>
> Clear Skies to all,
> Phillip J. Creed
>
> --- In comets-ml@yahoogroups.com, "cnj999" <jbortle@...> wrote:
>>
>> An interesting point, also I think touched upon in my article, was
>> how much more 18th and 19th century astronomers could "see" when it
>> came to difficult objects, compared to what amateur's today accept
>> as "visible". It's indeed rather shocking.
>>
>> As I recall, the great 19th Harvard astronomer G.P.Bond, states in
>> one of his books that the planet Venus is always visible to the
>> unaided eye in daylight at Cambridge (MA) providing its elongation
>> from the Sun is greater than 5 degrees. Near superior conjunction,
>> its magnitude would only be around -3.5 . Astonishing to most today,
>> perhaps, but true providing the sky is very clear. In fact, with
>> binoculars and using suitable cautions, Venus can be followed to
>> within just a dozen arc minutes of the solar limb!
>>
>> JBortle
>>
>
>
>
>
>
> Comet Observations List: http://groups.yahoo.com/group/CometObs/
> Comet Images List: http://groups.yahoo.com/group/Comet-Images/
>
> NOTICE: Material quoted or re-posted from the Comets Mailing List
> should be indicated by:
>
> Comets Mailing List [date]
> http://www.yahoogroups.com/group/comets-ml
>
>
>
>
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• ... And that s exactly why I like to observe Comets. My friends in the astronomy clubs I ve belonged to go out and look at the same Messier objects and NGC s,
Message 1 of 12 , Nov 2, 2006
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>From: "Maciej Reszelski" <macres@...>
>To: <comets-ml@yahoogroups.com>
>Subject: Re: [comets-ml] Re: Sungrazing comet visibility
>Date: Wed, 1 Nov 2006 18:00:55 +0100
>
>I always use David Levy's sequence
>that comets are like cats :) unpredict.
>
>That's what the comets are famous for me. You really never know....
>
>
>Best regards,
>Maciej
>

And that's exactly why I like to observe Comets.
My friends in the astronomy clubs I've belonged to go out and look at the
same Messier objects and NGC's, over and over again. I like to kid them
that it looks the same as the last time.
Some of the more serious observers like tracking down 17th magnitude Arp
objects, and only point thier big Dob's to a comet after I bring it to thier
attention.

I like looking at comets because they can look different from night to
night, and if they happen to pass near to a deep sky object, then Bonus!

I say, let the Comets take you on a tour of sky.

Carey

_________________________________________________________________
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• ... That the transparency of an 18th or 19th century sky was rather better than today s is undoubtely true. However, I think that in many instances the
Message 1 of 12 , Nov 2, 2006
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--- In comets-ml@yahoogroups.com, "Phil" <pcreed4863@...> wrote:
>
> John,
>
> I am not that familiar with the specific observations of astronomers
> in prior centuries, but I may have a theory...
>
> ...that it WAS indeed much clearer.
>

That the transparency of an 18th or 19th century sky was rather better
than today's is undoubtely true. However, I think that in many
instances the relative deterioration is highly exaggerated. I've seen
and read a number of presentation and papers regarding how serious the
atmospheric pollution has become. But, at the same time, the very fact
that I can today match the best observers of 19th century when it comes
to detecting objects in extreme proximity to the solar disk, makes it
clear that the obscuration can not be dramatically different. Likewise,
while I supposedly reside in an area considered to suffer from very
large amounts of airborne particulates (New York State), on any
reasonably clear day my ground visibility is 50 miles or better.
Viewing an object at significant elevation above the horizon should
encounter much less interference. Further, at such times any strong
solar areole often does not exceed 1-degree in extent. These factors
being so, conditions can't really be all that bad.

I honestly do believe that the lack of such extreme reported
observations in recent decades is simply the result of observers
considing them to be totally impossible out of hand and therefore
making not attempts whatever to determine what their respective limits
actually are.

JBortle
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