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C/2007 N3 (Lulin)

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#1 Rev_Aaron

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Posted 28 December 2008 - 08:04 AM

From my log, 12-28-08, using 8" dob:

Observation from Kirby Storter Roadside Park in Big Cypress National Preserve, Florida. 1025 UTC - C/2007 N3 (Lulin). Wow! Very bright. Very easy at 90x in the XT8. Nicely formed coma like an unresolved globular, centrally concentrated with an even linear dropoff in brightness from center to halo. About 3' across. No tail seen. Using the defocused-star method, I estimate magnitude at around 8. About 5 degrees above horizon. Considering this is well within the Miami light cone and at a very low elevation, this should be at least a suburban object with any kind of scope. Also observed at 120x and 170x. Visible with effort and averted vision in the 10x50 Resolux's. This soon switched to direct vision as the comet rose away from the Miami light cone (1050 UTC).



#2 Special Ed

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Posted 28 December 2008 - 08:13 AM

Nice catch and very good report! :waytogo:

#3 Rev_Aaron

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Posted 29 December 2008 - 10:09 PM

I have created a list of links for those wanting more information about this comet:

Caffeinated Astronomy Comet Lulin Links

#4 Special Ed

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Posted 30 December 2008 - 09:31 AM

Rev_Aaron,

Thanks for the links. If you don't mind, I'll post my observation here--maybe we can make this the Comet Lulin thread for the next few months. :)

I observed C/2007 (Lulin) this morning for the first time. Conditions were cold (30° F/ -1° C) and very windy. It was hard to get the stars on the horizon into focus. I started out about 5:15 AM local time (1015 UT) by walking out into the pasture where I could get an unobstructed view to the ESE with the 12x36 image stabilized binoculars. The comet was about 5° above the horizon but I spent 15 minutes looking and could not spot it. The zodiacal light was fairly bright.

By this time, Scorpius and Libra had risen enough that I could use the telescope set up back at the house. Using the Astroscan at 29x, I found Comet Lulin almost immediately. I pumped up the mag to 37x but with the turbulent atmosphere and low altitude of the comet, the view was not pleasing so I went back to 29x for the sketch (also I could include Beta Sco in the wider fov).

Using the Sidgwick method, I estimated M1= 8.3. The degree of condensation = 2 and the diameter appeared to be ~10'.

Even though the skyglow from the Sun began to intrude by 1130 UT, the comet was at a higher altitude by then and held its own against the brightening sky for a while.

While the comet is still low in the early morning hours, I would recommend any observer having a good chart to find it. Let's hope Comet Lulin fulfills its promise and gives us a great show in the coming months. :cool:

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#5 Rev_Aaron

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Posted 30 December 2008 - 12:43 PM

Excellent! I love the sketch, and your observation has been added to the link page.

#6 Special Ed

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Posted 31 December 2008 - 11:48 AM

Thanks, Aaron. :)

#7 Rev_Aaron

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Posted 31 December 2008 - 09:32 PM

Addendum: I have now seen this comet from the city of Fort Myers (under a street light, no less!) making this an official urban comet :) My observation this morning, also with the 8", has strengthened my hopes that this will be a very satisfying comet.

#8 Special Ed

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Posted 01 January 2009 - 10:50 AM

Well, I'm glad you got to see it again but I feel this would be a hard object to spot right now in LP skies unless one knew exactly where to look. Like most dim objects, once it has been spotted, it's easier to find the next time.
BTW, Carlos Hernandez provided some links on this thread in the Sketching forum that you might want to include on your webpage. :)

I observed Comet Lulin again this morning (New Year's Day 1030-1130 UT) under very cold and clear conditions. I tried for it once again with the 12x36 IS binoculars under very dark skies (NELM 6+ in the vicinity of the comet) and thought I could just barely detect it at the threshold of vision.

Switching over to the 108mm reflector, it was still close to its position on 30 Dec.--not much apparent motion yet. Conditions were very cold (7° F/-14° C) but thankfully calm. Even still, the focuser on the Astroscan (always a weak point) froze up and I had to work to free it.

The seeing and transparency were better than my last observation and Lulin's altitude was a little higher, so I was able to refine my previous estimates. I now put the diameter a little smaller, ~8 arcminutes, and the DC= 3. The magnitude appears about the same at 8.3.

I've updated the sketch with the comet's latest position:

Attached Files



#9 Rev_Aaron

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Posted 01 January 2009 - 01:37 PM

Great sketch! Thanks for the link.

#10 Special Ed

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Posted 01 January 2009 - 04:07 PM

Thanks, RevAaron--looking forward to your next observation report. I hope others get a chance to start chasing this comet. I'm fortunate right now because I'm on Christmas break, but I only have a few more days...

#11 NotThePainter

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Posted 02 January 2009 - 07:31 AM

Using Canon 15x50IS binoculars.

See http://notthepainter...c2007-n3-lulin/ for a viewing report.

#12 Rev_Aaron

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Posted 02 January 2009 - 11:49 AM

Nice! I really like your blog, too. Your writing style reminds me of mine. I'm going to add your observation to mu Lulin page.

#13 Special Ed

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Posted 02 January 2009 - 02:17 PM

Paul,

I enjoyed reading your report and I'm glad you hung in there until you found the comet. It would be fairly inconspicuous, even when using a fine instrument like the Canon 15x50 IS binoculars.

I think RevAaron and others have compared Lulin's appearance to an unresolved glob--M80 is close to the same angular size and magnitude and is in the neighborhood. It would be relatively easy to mistake one for the other right now. :)

#14 Rev_Aaron

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Posted 03 January 2009 - 07:55 AM

UPDATE:

I finally had time for another proper observing session this morning. From Fort Myers, FL, NELM was 4.5. Lulin was about 10 deg above the horizon when I first caught it with the 8" dob at 60x. Appearance unchanged from my previous sessions, I still think the best comparison is an unresolved globular. Having found the exact location, I decided to see what it looked like through some smaller instruments. My f/5 80mm achro showed it, but only because I knew exactly where to look. No luck with the 10x50's, but just as the eastern sky started to brighten, I was able to pluck Lulin out of the skyglow with my 15x70 Oberwerks. :) A nice session.

#15 Special Ed

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Posted 03 January 2009 - 09:42 AM

RevAaron,

Nice report--thanks for the update. :) I was out again this AM too (between 1030 and 1130 UT) looking at the comet and made a new sketch. I included Lulin's position from my Jan. 1st observation to stay oriented.

The wind was calm, NELM in the vicinity of the comet was 6.0+, but the transparency was only average. Like RevAaron, I felt the comet's appearance was essentially unchanged.
m1= 8.3 DC= 3 Diameter= ~8'

I took the opportunity to look at Lulin at 37x and 42x. The coma appeared a little irregular at those higher magnifications. I also tried with the 12x36's but only suspected the comet.

The temperature was 27° F (-3° C) but after my last observation with temps at 7°, 27° felt positively balmy! :grin:

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#16 markseibold

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Posted 03 January 2009 - 03:18 PM

Rev Aaron and Special Ed

Thanks for posting the heads up on Comet Lulin.
Very nice sketch Ed!

As I am always curious to know right away, where is it? I go to many sites and I see no reference to the date or RA, DEC or mention of constellations. Or I bring up outdated website info that is still without a date from years ago.

Here is one site I thought was nice for a rough and fine sky chart...
http://www.heavens-a...ed&alt=0&tz=CET

But again, is it just me? I see no mention of a date on the charts. I would think if any profession in the world, that astronomy would be the first to always indicate dates in documentation as timing is so critical with change in the sky.

Mark

#17 Rev_Aaron

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Posted 03 January 2009 - 03:30 PM

I have never been happy with the comet finder charts I could find online, so I started making my own with Cartes du Ciel. It's the only way to make sure you have a chart that is up to date and meets your own needs. That being said, there are a few sites that offer decent finder charts. I have tried to compile a few useful links related to comet Lulin on this site:

Caffeinated Astronomy Comet Lulin Links

Maybe you can find something useful there :D

#18 djeber2

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Posted 03 January 2009 - 04:43 PM

Hey Rev, I tried that Lulin link, but it is a link to a BBC entertainment webpage.

#19 djeber2

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Posted 03 January 2009 - 04:47 PM

Rev, I did get there thru the other link in your signature line. Thanks for the info!!

#20 Rev_Aaron

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Posted 03 January 2009 - 05:06 PM

Aw! Apologies. I was seeing who the new Doctor Who was :o Here's the link:

http://site.caffeina....com/lulin.html

#21 Special Ed

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Posted 03 January 2009 - 11:35 PM

Thanks, Mark. RevAaron has some good skychart links on his webpage. Here is another courtesy of comet guru Tony Cook:
Tonk's comet charts link :)

#22 Rev_Aaron

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Posted 06 January 2009 - 01:52 PM

Thought everyone would like to know that Lulin now officially has three tails! Check out this link to an image from the Lulin observatory:

http://yeiht.y234.cn/wordpress/?p=1239

#23 Tonk

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Posted 06 January 2009 - 02:45 PM

Its arguable that there are actually only two tails. One being the broad and fan like dust tail that is spreading out behind the comet from our view point on both sides of the comet. It should lie in the plane of the comets orbit. This anti-tail effect is often seen when a comet is crossing the plane of the Earth's orbit. This effect is often transient as the plane crossing for most comets is short lived. This idea is supported in that a pair of these tails (in the image) are colinear and on either side of the comet.

However Lulin is unsual in that its orbit inclination is 179 degrees and the comet is thus spending a long time crossing Earths orbit. So the double tail view point should persist for a long time.

The 3rd tail is most likely the ion tail and should lie on the line extended from the sun to the comet.

So my prediction is a pair of tails will remain colinear on each side of the comet because they are in fact the same dust tail. The angle of the ion tail to these colinear tails will vary to some amount as the sun/comet/earth angle changes with time. Howver geometry wise as viewed from Earth the ion tail will always lie at a small angle to the dust tail

Only time will tell if I'm right :)

#24 Jeremy Perez

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Posted 06 January 2009 - 03:04 PM

Aaron, thanks for posting that link, and Tonk, thanks for the analysis. That sounds like a good forecast. I think I'm motivated enough by that to get up early in the next day or two to try and put my eye on it.

#25 deSitter

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Posted 06 January 2009 - 03:39 PM

This is a very odd comet - it's moving almost exactly in the ecliptic plane but counterclockwise around the sun, that is, its inclination to the ecliptic is almost 180. Starry Night shows this comet making a close approach to Saturn on the night of Feb 23, passing within 2 degrees around 9 PM EST while nearly directly on the ecliptic. It should be a naked eye object in dark skies, right at mag 6, but of course it could still brighten considerably. It will only be about 1/2 an AU distant - about the distance to Venus - and moving VERY fast through the sky, so fast that it will speedily track out of the field of view of a driven scope.

In other circumstances this would have been a very dangerous comet, since it moves in the same plane as Earth.

More interesting stuff - it passes close to Regulus - less than 1/2 degree - width of the Moon! - on the 27th at about 7:30 PM EST, It appears that for observers in far northern Europe and Asia, the comet comes near to being occulted by the Moon, near the Beehive!

Another odd fact - because we see it edge on, the tail will change directions as we pass through the plane of its dust fan near its opposition on the 26th.

Thank God we are modern, else one could only imagine what disasters astrologers would foretell, with a comet conjunct Saturn in Virgo opposite the Sun..

-drl






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