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BSJ
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'Comet of the Century' Not Brightening as Expected new
      #5756118 - 03/25/13 12:41 PM

http://www.space.com/20367-comet-ison-brightness-predictions.html

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Tonk
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: BSJ]
      #5756420 - 03/25/13 03:26 PM

This has been discused on Yahoo's Comets-ML over the last couple of months. Yup possibly yet another comet that has unecessarily be over projected on its light curve far far too early Its also appearing to be typical behaviour for many first time Oort Clound visitors

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LivingNDixie
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Reged: 04/23/03

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Re: 'Comet of the Century' Not Brightening as Expected new [Re: Tonk]
      #5756452 - 03/25/13 03:37 PM

Comet McNaught was the comet of the century. Those darn Aussies got to see it well.

Maybe we will have better luck in the 22nd century....


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Rich (RLTYS)Moderator
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: BSJ]
      #5756540 - 03/25/13 04:37 PM Attachment (49 downloads)

To All

Imaged C/2012 S1 Ison with the Slooh T2hm scope on 3/24/13. I noticed that Ison doesn’t seem as bright as in my previous images and seems to have lost its tail or just not as obvious. I have read reports that Comet Ison is not brightening as much as it should be with the comet still between 15th and 16th magnitude. My image suggests that this is true. But if you look closely at the image the brighter pseudo nucleus appears not to be quite centered with the fainter outer coma emitting toward the northeast. Will Comet Ison be the spectacular comet everyone wants?

Rich (RLTYS)


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skyquest25
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Reged: 08/22/12

Loc: United States
Re: 'Comet of the Century' Not Brightening as Expected new [Re: Rich (RLTYS)]
      #5756597 - 03/25/13 04:56 PM

As unpredictable as comets are, I'm going to be positive and hope for a bright one

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blb
Post Laureate


Reged: 11/25/05

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Re: 'Comet of the Century' Not Brightening as Expected new [Re: skyquest25]
      #5756766 - 03/25/13 06:30 PM

Quote:

As unpredictable as comets are, I'm going to be positive and hope for a bright one...




and not be surprised if it isn't.


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Phillip Creed
Idiot Seeking Village
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: blb]
      #5760733 - 03/27/13 04:25 PM

Comet Light Curves 101:

The equation used to calculate a comet's brightness based on its position is:

m1 = M + 5*log (d) + 2.5*n*log (r)

where:

m1 = total integrated magnitude
M = magnitude when the comet is 1 A.U. from both sun and earth
d = distance from earth, AU
r = distance from sun, AU.

While the mathematics might justify a dazzling apparition for Comet ISON, the problem is it's solely because the comet comes within 0.0125 A.U. of the sun (making the 2.5*n*log (r) term very negative). Comets brighten by a factor of 2^n as their heliocentric distance is cut in half, but we don't know what the brightening factor "n" is. For a new comet, n is often assumed to be 4, but it's just a guess.

Right now, the comet is 15th magnitude and is 4.32 A.U. out from the sun and 4.17 A.U. from earth. If you assume a default of n = 4, you get:

m1 = 5.5 + 5 log d + 10*log (r).

Set r = 0.0125 AU at perihelion (d ~ 1.00 and this term effectively zeroes out), and you get:

m1 = 5.5 + 10*log (0.0125), or m1 = -13.5.

BUT...

if n = 3 (very possible; Comet PanSTARRS more or less followed this behavior), then the light curve that best fits its performance right now is:

m1 = 7 + 5*log(d) + 7.5*log (r).

At perihelion, then,

m1 = 7 + (0) + 7.5*log (0.0125), or -7.3.

Just a change in n = 4 to n = 3 would reduce the comet's peak brilliance by 6 magnitudes! The best show will be about a week or two other side of perihelion, when the comet will be much, much dimmer.

Conversely, set n = 5 or more, and it'll get scary bright.

Clear Skies,
Phil


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MessiToM
scholastic sledgehammer
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Reged: 12/21/09

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Re: 'Comet of the Century' Not Brightening as Expected new [Re: Phillip Creed]
      #5760796 - 03/27/13 04:55 PM

Come on you Debby downers, lol be optomistic. I need this comet to put on a show. lol

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Tommy5
Carpal Tunnel


Reged: 03/28/04

Loc: Chicagoland
Re: 'Comet of the Century' Not Brightening as Expected [Re: MessiToM]
      #5767196 - 03/30/13 05:19 PM

Comet Kuhuetek anyone?

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orion61

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Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: 'Comet of the Century' Not Brightening as Expected new [Re: Tommy5]
      #5802161 - 04/16/13 09:11 AM

Hale Bopp is my favoritet so far, that Blue and Gold tail was spectacular!
Lets hope for the best, BUT, I gotta feeling......


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nytecam
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: Rich (RLTYS)]
      #5807292 - 04/18/13 06:06 PM Attachment (28 downloads)

Quote:

To All - Imaged C/2012 S1 Ison with the Slooh T2hm scope on 3/24/13. I noticed that Ison doesn’t seem as bright as in my previous images and seems to have lost its tail or just not as obvious. I have read reports that Comet Ison is not brightening as much as it should be with the comet still between 15th and 16th magnitude. My image suggests that this is true. But if you look closely at the image the brighter pseudo nucleus appears not to be quite centered with the fainter outer coma emitting toward the northeast. Will Comet Ison be the spectacular comet everyone wants? Rich (RLTYS)


Here's a quicky shot from tonight Apr 18 of Comet ISON ~m16.5 with hint of tail to east [left] immediately above a bright 1st quarter moon - better stacked shot tomorrow

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nytecam
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: nytecam]
      #5808843 - 04/19/13 02:38 PM Attachment (30 downloads)

Here's a deeper pic from last night - the comet seems to have faded since my April 1st shot but still hints of a tail

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Tonk
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Reged: 08/19/04

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Re: 'Comet of the Century' Not Brightening as Expected new [Re: nytecam]
      #5808934 - 04/19/13 03:25 PM

Quote:

Will Comet Ison be the spectacular comet everyone wants?




Will you still be holding your breath .... ?


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BrooksObs
professor emeritus


Reged: 12/08/12

Re: 'Comet of the Century' Not Brightening as Expected new [Re: Tonk]
      #5809152 - 04/19/13 05:41 PM

I'm afraid that Comet ISON is falling further and further behind its early brightness predictions with each passing week. In fact, images obtained over the past three months mostly fail to indicate any brightening trend at all.

The comet is currently inside the orbit of Jupiter. I would note that at this same distance Comet Hale-Bopp was already visible in ordinary binoculars! While I wouldn't totally write off this object just yet, I'm increasingly having a bad feeling about its future potential.

BrooksObs

Edited by BrooksObs (04/19/13 09:06 PM)


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buddyjesus
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: BrooksObs]
      #5809800 - 04/19/13 11:12 PM

this comet does have one thing going for it and that is the Earth will be close to the comet on the way in and out of the inner solar system. I am trying to be optimistic...

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Rich (RLTYS)Moderator
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: BrooksObs]
      #5810089 - 04/20/13 06:06 AM

Quote:

I'm afraid that Comet ISON is falling further and further behind its early brightness predictions with each passing week. In fact, images obtained over the past three months mostly fail to indicate any brightening trend at all.

The comet is currently inside the orbit of Jupiter. I would note that at this same distance Comet Hale-Bopp was already visible in ordinary binoculars! While I wouldn't totally write off this object just yet, I'm increasingly having a bad feeling about its future potential.

BrooksObs




I agree, Ison does not appear to be brightening.

Rich (RLTYS)


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brianb11213
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: Rich (RLTYS)]
      #5810092 - 04/20/13 06:13 AM

Quote:

Ison does not appear to be brightening.



Exactly as "expected" by those of us who have seen lots of "fizzles" ...


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rmollise
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Re: 'Comet of the Century' Not Brightening as Expected new [Re: MessiToM]
      #5810885 - 04/20/13 01:18 PM

Quote:

Come on you Debby downers, lol be optomistic. I need this comet to put on a show. lol




That's just what I said in 1973!

Edited by RLTYS (04/21/13 07:20 AM)


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krp
Vendor. DarkSiteFinder.com


Reged: 11/10/10

Loc: Central Illinois
Re: 'Comet of the Century' Not Brightening as Expected new [Re: rmollise]
      #5811540 - 04/20/13 06:53 PM

I just hope this comet is brighter than Panstarrs. I was just watching this video about a potential meteor shower caused by Ison in January: http://www.youtube.com/watch?v=_eSYxvUWwVk
But, even if that happens, the meteor shower will be invisible.


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stevecoe
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Reged: 04/24/04

Loc: Arizona, USA
Re: 'Comet of the Century' Not Brightening as Expected new [Re: krp]
      #5811588 - 04/20/13 07:18 PM

And just how does one know about an invisible meteor shower?

Isn't that like military intelligence or Senate ethics committee?

Weird, man, weird;
Steve Coe


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