#181  
Old 23-12-2011, 12:06 PM
Ian Cooper
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The Grest Cometr debate Starts!

Fringe_dweller has put the cat in amongst the pigeons, so to speak. This debate has occurred almost everytime in recent memory that there have been contenders for the title.

In the past I have delivered talks on this subject and it is my contention that there are two elements that go either separately, or together, to make up a "Great Comet." They are, in no particular order, 'brightness,' and 'size.'

A sky object/phenomemenon, daytime or night, that has great angular size will always impress most people by that dimension alone. Something small, but very bright (the Full Moon e.g.) will do likewise. Combine the two and there are no arguments (Comet McNaught in Jan 2007).

In 1996 and 1997 we had two very contrasting 'Great Comets.' The unexpected Hyakutake in 1996 put on a display for those who saw it that will not be forgotten. In a rural location like mine the tail was a classic search-light beam like something from a medieval wood-cut drawing, and stretched out to around 70 degrees long from the Northern Hemisphere. Some say that Hyakutake went to 90 degrees, but I can find no photgraphic eveidence to back this up. The coma was a massive 2 degrees across, like a swollen, diffuse full moon. Yet from most cities the tail only stretched out to about 10 degrees at best.

The highly anticipated Hale-Bopp a year later never grew to much more than 25 degrees long at best, but once again a huge coma, slightly brighter than Hyakutake's, followed by a highly reflective dust pume that was easily seen from the greatest cities of the northen hemisphere, meant that H-B was a stand out in the memory of anyone who bothered to glance up at it. Being the longest visible-to-the-naked-eye comet also helped cement H-B as a great comet.

When I started to compare the current size of Lovejoy to the remarkably similar Ikeya-Seki of 1965, the numbers are very much alike. Obviously Lovejoy 2011 W3 doesn't possess a bright coma/nucleus like I-S, but the brilliance, and growing length of the tail certainly makes up for that.

Considering the comments below by Terry himself regarding the comet's perigee date, I would expect the tail to increase significantly, as did LINEAR T7 back in May 2004, as the comet makes its closest approach to earth. If that occurs then we should see the length numbers about the same as those for the great comets of 1880 & 1887.

When we add all of these factors up, as well as the reported magnitude near perihelion passage of -2.9. I will not be surprised if the title of, "Great Comet," is bestowed upon our magnificent celestial Christmas present!

Cheers

Coops
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  #182  
Old 23-12-2011, 12:25 PM
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kinetic (Steve)
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Quote:
Originally Posted by fringe_dweller View Post
what exactly is the criteria for a 'Great' comet? if what we observed this morning isnt a Great comet, i'm not sure what is!? Comet Lovejoy's tail was as bright as the southern milky way, actually much brighter as it rose, so what that puts it in the 3.5 mag surface brightness range, min, especially the brighter section of tail! i was comparing it to pointers and other bright stars, very comparible! we could easy see 25d naked eye tail by full visiblity .. in bright twilight, not much else left visible at comets altitude hmmm
Good points Kearn and Ian (above)
Hopefully everyone who captured great data doesn't just pic the best
frame from hundreds and post. There is a lot in even crappy data.
Have a look , for example, how bright the very last part of the
two tails are, compared to the Milky Way in this stack of my frames
that are before astronomical twilight starts.
Remember, that is the faintest part of a tail, normally.
This is a great comet. best views are yet to come, I believe.

Steve
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  #183  
Old 23-12-2011, 12:42 PM
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Visionoz (Bill)
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Originally Posted by jiahao1986 View Post
Hi,

This is Jack from Singapore. Really can't resist and just purchased a ticket to Perth for tomorrow.

Anybody in Perth heading to dark sties for a fulll-nighter on Saturday? I would desperately love to join since I've never been there thus not familiar with the place at all. Don't mind sharing petrol cost or even mileage. Simply can't miss a great comet like this after the miserable experiences with comet McNaught.

Appreciate it folks.

Best regards,
Jack
Jack

PM me when you are in Perth - perhaps you can join some of us who might be heading to our ASWA's dark site @ Tammin (about 2 hours drive from Perth) for a 2-niter from Monday next week

HTH
Cheers
Bill
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  #184  
Old 23-12-2011, 12:55 PM
Ian Cooper
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Some further good points there Steve regarding the fainter end of the tail. I have always considered the portion of Milkyway in Ara/Norma as being bright. At this time of year it can be a 'phantom auroral ray,' for those of us sucked in by it.

On two successive mornings now I have seen the view shown in your picture. It is often hard to compare one diffuse object with another because of the varying angular sizes and the unequal light distribution. Clearly though the end of the tail is far brighter than the nearby Milkyway in Ara.

On March 25th 1996 I photographed the tail of Hyakutake extending up above the horizon for nearly 40 degrees, whilst the head remained 16 degrees below my horizon at best. The light of the majority of the Hyakutake tail visible to me on that night was still not as bright as the section of Milkyway that spurs off from Aquila west of Scutum.

Overall we may say that the coma is very faint, but even the end of the tail is possibly brighter than the LMC. The first ten degrees of tail though are very bright and visible from urban locations.

This is a great story unfolding and we are in the box seats for sure (once again, everything is as it should be).

Cheers

Coops
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  #185  
Old 23-12-2011, 01:56 PM
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Thanks Coops for all that info, great reading.

Quote:
Originally Posted by CometGuy View Post
Hi Liz,

The comet is still moving towards earth, and is closest at 0.5 AU in early January when the comet's coma will pass near the south celestial pole (nice!). I imagine the tail would have become quite weak by then and may be difficult to see.

This comet is very similiar to the Sungrazing Comets of 1880 and 1887, which remained visible only 3 weeks past perihelion. So if history is anything to go by then we don't have too much time to get the best views, maybe until the end of the year.

Terry
Thank you Terry, wonderful news!!

Quote:
Originally Posted by jiahao1986 View Post
Hi,

This is Jack from Singapore. Really can't resist and just purchased a ticket to Perth for tomorrow.

Anybody in Perth heading to dark sties for a fulll-nighter on Saturday? I would desperately love to join since I've never been there thus not familiar with the place at all. Don't mind sharing petrol cost or even mileage. Simply can't miss a great comet like this after the miserable experiences with comet McNaught.

Appreciate it folks.

Best regards,
Jack
Good on you Jack, wishing you clear skies, and hope Bill and friends look after you.
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  #186  
Old 23-12-2011, 02:07 PM
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Hi Folks got my first look at comet lovejoy this morning and wow what a stunner , as soon as we were out of the car there she was beaming up into the sky .Dragged a work mate along who had never seen a comet before and she was blown away,lucky to see that as your first comet.Got lucky with the clouds and managed a few shots.
cheers
Baz
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  #187  
Old 23-12-2011, 02:12 PM
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Great images Baz, what a great experience!!

Have seen this wonderful comet, but not in its full glory, maybe tomorrow.
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  #188  
Old 23-12-2011, 02:20 PM
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A couple of images for you Terry. One through my 80mm scope at around 450mm focal length and a wideangle using a Canon 17-40mm f4 lens. Both images using a Canon 400D.
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  #189  
Old 23-12-2011, 02:24 PM
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Brilliant, Andrew!
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  #190  
Old 23-12-2011, 02:29 PM
callingrohit (Vivek)
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As more and more fantastic and amzing pictures keep flowing into this thread, more and more desperate I'm getting to see it and then try my luck with photographying it.

Damn daylight, lets keep rolling the 2 hours +/- the dawn.

It's an awesome gift for all astronomers this christmas - Thank you Mr Lovejoy, may you find about 100 more of such comets.

Now, any pointers or best place to see it from near Brisbane ?

Thanks
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  #191  
Old 23-12-2011, 02:46 PM
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I hope your enjoying my Xmas present, btw I am just charging $2 per look. Please do a bank transfer to....

Sorry poor attempt at humour! Anyway many thanks to all the people who have been posting images. Look how much more intense the tail is compared to the milky way

Andrew, I'd like to get that image of the coma to measure the comets position if thats OK? I'll PM you shortly.

Terry
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  #192  
Old 23-12-2011, 03:22 PM
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The Great Cosmic Beam

Wow, fantastic images everyone. Just keeps getting better. Had some clouds last night - showed up at 2.30 - but decided to hang around and try some longer exposures. Took this one just before start of astro twilight at 105 mm (+ zoomed a little more in post).

Terry, can I propose a new name for your comet. The Great Cosmic Beam! And yeah, you should be charging per view/image. Or at least demand a front row seat on the next ISS flight?!
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  #193  
Old 23-12-2011, 07:14 PM
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G'day All ,
Can anyone let me know what time tomorrow morning i should be looking for Comet Lovejoy & how far above the horizon to look .
As i live in suburban Adelaide will i need to find somewhere with altitude or just somewhere like an oval/park .
MTIA
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  #194  
Old 23-12-2011, 07:17 PM
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G'day All ,
Can anyone let me know what time tomorrow morning i should be looking for Comet Lovejoy & how far above the horizon to look .
As i live in suburban Adelaide will i need to find somewhere with altitude or just somewhere like an oval/park .
MTIA
Hi Ronnie

I'd start from 3am, towards the East. The tail extends up into Scorpius.

From 3am, you'll see the tail rising higher until it's lost in the twilight from around 4:30am.
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  #195  
Old 23-12-2011, 07:24 PM
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Hi Ronnie

I'd start from 3am, towards the East. The tail extends up into Scorpius.

From 3am, you'll see the tail rising higher until it's lost in the twilight from around 4:30am.
Thank$ Iceman
Do i need to be outside suburbs with lot's of houses or will a park/oval do to view & how high above horizon ?

Ronnie
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  #196  
Old 23-12-2011, 07:28 PM
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The less light pollution the better, and it will be low on the horizon so a good view to the East is essential.
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  #197  
Old 23-12-2011, 07:38 PM
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Yes thinking of going out again in the morning, might have to head east this time to get away from the light pollution. I usually go out near Mt Pleasant for a view.
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  #198  
Old 23-12-2011, 07:43 PM
swannies1983 (Dan)
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I will venture to the same spot I went to this morning (near McLaren Vale). Surprised how dark it was there, and only 20mins from my house.
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  #199  
Old 23-12-2011, 07:49 PM
Ronnie (Ronnie)
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The less light pollution the better, and it will be low on the horizon so a good view to the East is essential.
Thank$ i will check for cloud sounds like i need to go to Mt Lofty ranges as if i get out of the burbs East that where i will end
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  #200  
Old 23-12-2011, 07:58 PM
swannies1983 (Dan)
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Hoping for clear skies Ronnie. There might be some cloud around in the morning so perhaps go east of the ranges if you can.
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