[Chaos-l] Nice Animated GIF Of Comet Lulin

Wed Feb 25 21:37:41 EST 2009

I think those streaks that kept appearing were satellites rather than meteors.  I did "mispeak" about the stars "slewing" past, though.  Let me clarify my hypothesis...

Meteors probably would have been to brief to appear at in the time-lapse movie and even if they did show up, they would have passed through the field way too fast to be appear like for so long in that movie.  Each image of the "movie" showed a steak about an "inch" long in the frame.  Orbiting satellites would also have moved too quickly to appear as short streaks in each exposure.  If they were geosynchronous satellites, the apparent motion (which showed up a the short streak in each image) would be due not to the relative motion of the satellites, but to the slewing of the telescope to counter the rotation of the Earth (and make the stars appear stationary).  It seems to me that the telescope slewing speed would be the only motion slow enough to keep those lights in the frame for so long (since even a split second in that film would have to represent a minute or more in real time).  Furthermore, the position of the meteor at that time had to be near the ecliptic (since it was near Saturn) which is where you would expect to see geosynchronous satellites.

I had some similar pair of apparitions appear in some webcam images I made a few years back, and this was the explanation given to me by someone on a listserve.   I was hoping they were invading alien ships, but I must admit that the satellite explanation seems more likely.  The guy even looked up some satellites and told me which ones they probably were.  Now that might be interesting to figure out--which satellites they could have been if that's indeed what they were....

Chris Breivogel
CHAOS member wanna-be

-----Original Message-----
From: chaos-l-bounces at rtpnet.org on behalf of Terry Crook
Sent: Wed 2/25/2009 8:17 PM
To: robertnielsen at nc.rr.com; chaos-l at rtpnet.org
Subject: Re: [Chaos-l] Nice Animated GIF Of Comet Lulin

I now know what the 'fuzzy' is!
 From the Sky & Telescope site, 
http://www.skyandtelescope.com/observing/objects/comets/35992534.html:

There's lots more photos & text, including much 
on anti tails & the comet's peculiar motion/orientation.

On 2/24, 8:42, I wrote:
Yes, I'm familiar with the ion tail vs the more visible dust tail.
However, this fuzzy area is preceding the comet 
coma, not trailing away (from the Sun) as is normal.
Possibly some gas eruptions from the head of the 
coma, illuminated and/or excited by solar radiation?
It seems in synch with the comet's motion, at 
least for now/during this photo series.

Someone tho't the streaks were earth satellites 
but I'd bet on meteor trails. The former would 
leave a longer trail than the meteors, it seems 
to me. Surely we may be able to identify the 
meteor shower?  His reference to camera slew is 
weird, as none of the star trails have moved 
during the ~2-minute duration/exposure.

There was one isolated bright spot very briefly, 
just ahead & above of the comet; possibly electronic noise?

OTOH, I can't make out NGC 4073 but then you know 
much better than I what to look for & have better eyesight!

  At 04:24 PM 2/24/2009, you wrote:
>Terry,
>
>An explanation of why we see two tails (one a 
>dust tail and one an ion tail) is visually given 
>at: http://www.sidleach.com/comet_c2007_n3_lulin_antitail.htm.
>
>I'm not entirely sure ... but looking at the 
>rough general area of the sky where Comet Lulin 
>was last Saturday, and matching up some of the 
>stars, I would say the bright star is beta 
>Virginis, or Zavijava.  And I think the faint 
>galaxy above the comet when it starts is NGC 
>4073 ... although there are a lot of galaxies in that area.
>
>Robert
>
>Terry Crook wrote:
>>Remarkable pix, thanks! I would have gone out 
>>to look for it locally (with binocs) but have 
>>been fighting a nasty sinus infection lately!
>>Two questions (for anyone):
>>         What is the star in the upper right center?
>>         If the Sun is to the right (w/ tail 
>> extending behind comet), what is the variable cloud ahead at about 1'oclock?
>>
>>At 12:02 PM 2/24/2009, Robert Nielsen wrote:
>>>Everyone,
>>>
>>>This has been making the rounds on some 
>>>astronomy forums: http://www.ccdargo.com/lulin.gif
>>>
>>>It's a really nice animated GIF of Comet 
>>>Lulin, taken last Saturday night where 61 
>>>images cover about 2 hours of the comet's movement against the star background.
>>>
>>>Credit: Tom Carrico
>>>
>>>Robert
>>>
>>>_______________________________________________
>>>Chaos-l mailing list
>>>Chaos-l at rtpnet.org
>>>http://rtpnet.org/mailman/listinfo/chaos-l
>>
>>Taurus Terry in Chapel Hill
>>35ï¿½ 55' 47"N, 79ï¿½ 01' 00"W

Taurus Terry in Chapel Hill
35ï¿½ 55' 47"N, 79ï¿½ 01' 00"W  

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