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Comet C/2007 N3 (Lulin)

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Author Topic: Comet C/2007 N3 (Lulin)  (Read 15912 times)
martinastro
Martin Mc Kenna
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« Reply #270 on: March 04, 2009, 07:32:14 pm »

Hi Tyler, you are spot on about the arc min - 1/60th of a degree.

Lulin last night really was the shadow of its former self. I could see it with the naked eye before and after moonset but it was not jumping out of the sky at all. With any strong LP it would have been invisible. In the binos it looked much smaller, but still fairly large, however with the naked eye using averted vision it seemed much larger which is something which can't be seen in a scope. Good old 'aperture effect' again. It was almost in the same bino field as M44.

Glad you seen it Tyler. By the way, nice job starting the new comet observing section on your site. I was delighted to see your passion for comets shining through the text. By the sound of things you are really getting into comets in a big way...there is no better phenomena in my opinion  Smiley. Maybe we will all get to see a great comet in the near future...fingers crossed. Who knows what will appear before the Summer - I'm ever the optimist.
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« Reply #271 on: March 04, 2009, 08:08:33 pm »

The weather is teasing me today  Undecided
After a cloudy morning\afternoon, it quickly cleared at ~17 hours. The sky became great and the sunset was beautiful (I will post some images later). But soonly, as it got dark at 18h. Sc/Ac clouds started to move quickly from S, so the sky became completely cloudy (with some gaps). I tried to observe lunar occultation at 19:15, have seen the star (HIP24252) in 5 minutes before an occultation, but then the thicker cloud arrived and I lost the star from view.
Also tried to find the comet with binoculars through gaps, once I have found delta Cancri, but 6-7m stars near the comet weren't visible (through the edge of upcoming cloud). Now it is getting worse. All my hopes are for the next night...

I'm not sure how you guys measure with arc minutes and such, but on the 24th the comet filled the whole FOV in my eyepiece which is 1 degree I think, but tonight was barely detectable with 1/3 the size of my previous observation.
Let me tell how I measure the comet diameter in minutes.
  One way is to precisely know a FOV of each of yours eyepieces (see below). Next move the comet to the edge of the FOV and estimate its size or just mentally divide FOV into 1/2, 1/3, 1/4, 1/10 etc and compare to the comet.
  Another way is more precise. Find two closest stars to the comet, imagine the comet between them (or maybe it is already there) and again, estimate the comet's size regarding to the distance between the stars (1/2, 1/3,...). It is even better to repeat the estimate with another pair of close stars, if possible. Next, measure the distance between stars in software and convert your "1/2" into arcminutes. I prefer to use this method, it usually gives me enough good quality (+/- 1'), if only the comet is steadily visible.


A bit offtopic: how to define precisely the FOV of an eyepiece?

If somebody knows a formula, please post it, it will be much useful

Defining it in experimental way is not such precise but easier in some cases. Tonight I observed the Moon (dia. 32.8') at 56x, and the FOV was ca. 3% bigger than the Moon diameter. So, it is 34' (+/- 1').
I used the same method to define binocular's FOV, it was less precise, of course.

« Last Edit: March 04, 2009, 08:20:10 pm by Roman White » Report Spam   Logged

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« Reply #272 on: March 04, 2009, 10:28:33 pm »

Wow sounds like you had an epic sky last night Martin  Smiley
M44 was just in my FOV (8 degrees) with the binos, but I guess I observed it after you did. I had to use adverted vision to spot it in the binos and scope too. I would have to say the naked eye limiting mag here is not quite to 4  Undecided I couldnt see any stars in cancer. I hope this changes this summer, or fall, as I might be moving to a darker location  Smiley (I can only hope at this point)

Thanks Martin, for some reason after getting my website going I just wanted to document every observation I make, whether it be meteorological, astronomical or photographical  Grin  It gives me something to do on cloudy nights.

Roman, here is a good link I found (and my FOV is actually 1.25 degrees on my 25mm piece and .54 degrees on my 9mm piece- that I never use lol)

http://www.csgnetwork.com/telefov.html
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« Reply #273 on: March 05, 2009, 12:13:29 am »

Quote
A bit offtopic: how to define precisely the FOV of an eyepiece?

If somebody knows a formula, please post it, it will be much useful
Time how long it takes delta Orionis (the top star in the belt) to drift across the whole field through the centre with the drive not running. The eyepiece actual field of view is 1 minute of orc for every 4 seconds. (Delta Orionis is very very close to the celestial equator, so the correction term for declination can be ignored)
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« Reply #274 on: March 05, 2009, 09:15:03 pm »

The Moon is a nuisance, but it's not a showstopper - here's Lulin and M44....

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« Reply #275 on: March 05, 2009, 09:26:22 pm »

Well done, Paul!  Smiley
Nice to see the comet in the close proximity to M44. Today I was printing a sky chart of the same area... actually I planned to observe it at Poltava gravimetric observatory (where I was going today). We had here nice clear sky between 13-17 hours, but then thick As clouds covered the whole sky... So we were only sitting inside a room and looking through a window on the cloudy sky...
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martinastro
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« Reply #276 on: March 05, 2009, 10:56:14 pm »

Paul, that's a beauty!, well done on catching it at such a photogenic place!

Observed Lulin through the scope tonight below M44 and despite moonlight and patchy cirrus cloud it looked great. There's a bright field star within the coma and I could trace the anti-tail for 1.5 degrees!. This comet is still putting on a show  Smiley
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« Reply #277 on: March 05, 2009, 11:10:49 pm »

Well, I'm just in from the cold again

Comet Lulin is still putting on a very good show tonight (March 5th) as it passes very close to the starcluster Messier 44, the 'Beehive' cluster. I observed this comet and cluster together with my 9x60mm binoculars at 7.30pm, and the comet is still visible with the help of averted vision. I noticed that it certainly is not as bright as it was only a few short nights ago, and is now receeding from Earth quite fast. I estimate it's magnitude at 5.5, and you can see from the photo that the tail has shortened a little, although the strong moonlight does not help.

I could not see it naked eye, though I would say that it would have been visible if the moon had not been so close. Still, a lovely sight to see, as this does not come around very often.

Details: Canon 40D, 135mm 'L' lens at f4, 12x30seconds stacked exposures at ISO 800.

www.flickr.com/photos/79652716@N00/3331994124/sizes/o/

Keith..
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« Reply #278 on: March 06, 2009, 12:15:51 am »

Wonderfully atmospheric image Keith.  Really first class stuff!!
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Regards and Clear Skies,

Dave.
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J41 - Raheny Observatory.
http://www.webtreatz.com
Equipment List here
martinastro
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« Reply #279 on: March 06, 2009, 04:10:14 pm »

Beautiful image keith, great colour and anti-tail  Smiley, which by the way looks very long even the Moonlight!

I moved your post over here to the official Lulin thread to keep track of things.
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« Reply #280 on: March 07, 2009, 09:34:48 am »

I have sent two reports to ICQ, this was the first time I'm sending it there. And I thought they didn't include my reports, but today I looked here and have seen my report too:  Smiley
Quote
COMET C/2007 N3 (Lulin)
     Total-magnitude and coma-diameter estimates (visual unless otherwise noted):
2009
Mar.  3.14, 5.3, 25' (J. J. Gonzalez, Leon, Spain, naked eye);
(...)
Feb. 24.17, 5.3, 20' (A. Amorim, Florianopolis, Brazil, 10x50 binoculars; clouds);
     24.12, 5.0, 25' (M. Goiato, Aracatuba, Brazil, 7x50 binoculars; clouds);
     23.90, 4.8, 30' (J. J. Gonzalez, Asturias, Spain, naked eye);
     23.12, 5.0, 25' (M. Goiato, Aracatuba, Brazil, 7x50 binoculars; clouds);
     23.07, 4.8, -- (T. Scarmato, Calabria, Italy, naked eye);
(...)
Feb.18.02, 5.7, 12' (V. Gonano, Udine, Italy, 10x50 binoculars; light pollution);
     18.02, 5.8, 11' (F. Zucconi, Lodi, Italy, 10x70 binoculars);
    17.98, 6.0, & 12' (R. Kostenko, Poltava, Ukraine, 7.6-cm reflector);
     17.82, 5.8, 14' (M. Reszelski, Szamotuly, Poland, 20x60 binoculars);
     17.66, 5.5, 23' (K. Yoshimoto, Yamaguchi, Japan, 7x35 binoculars);
(...)
They didn't include my Feb.23.90 report because J.J.Gonzalez observed directly at the same time. OK, I'll forgive it. Wink

P.S. The weather is still bad here, only one or two clear nights are possible on next week...
« Last Edit: March 07, 2009, 09:41:06 am by Roman White » Report Spam   Logged

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« Reply #281 on: March 07, 2009, 01:47:48 pm »

Good job Roman. Great to see comet observations being put to good use!  Smiley
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« Reply #282 on: March 08, 2009, 09:29:19 pm »

Well thursday night was probably that last I will see of the Comet, I believe it will dim to where it won't be visible before the moon begins to rise AFTER dark. But I did get one image of it and M44, nothing spectacular by any means, because I couldn't get the tracker set up before the fog rolled in (to see more fog, check out the link below)

http://tonightssky.org/account030509.html



Well hey, we made it to 20 pages! bring on the next big thing!
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« Reply #283 on: March 14, 2009, 05:56:53 pm »

I observed the comet on Mar.11 evening, between 21:25-22:35 (GMT+2).
Comet was in 4oS of kappa Geminorum.
Observing conditions: 0*C, clear sky, NELM ~4.2. The full Moon (low in E) was a great nuissance.

- in 22x32 binoculars: not visible

- in 76/700mm reflector: at magnification 35x, at the first glimpse I didn't see it. But 20-30 minutes after, as my eye got dark adapted (I was hiding from the Moon inside a shelter) I could barely see the comet with direct vision and a bit better but still faint with averted vision. It wasn't enough good visible to make precise estimates. ML=10.7m. Diffuse coma, with slight brigtening towards center.

C/2007N3 (Lulin):
2009 Mar.11.85 UT: m1=6.8:, dia.=&7', DC=2?, no tails, 7.6cm reflector (35x)
[altitude 52*; strong moonlight interference]
(estimates are unsure)

------------ --------- --------- ----
*ICQ format*
   2007N3  2009 03 11.85  S  6.8:TK  7.6L 9  35 & 7    2            ICQ
------------ --------- --------- ----
« Last Edit: March 15, 2009, 02:45:29 pm by Roman White » Report Spam   Logged

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« Reply #284 on: March 15, 2009, 09:20:14 pm »

Sketch


(my comet observations page updated)
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