[AZ-Observing] Re: Glimpse of Lulin; comet orbit model ?; Saturn animation, etc.

  • From: Gene A Lucas <geneluca@xxxxxxxxxxxxx>
  • To: az-observing@xxxxxxxxxxxxx
  • Date: Mon, 09 Mar 2009 00:39:07 -0700

Hi Tom,

Regarding seeing the two tails on Comet Lulin, it occurs to me that this 
is a result of our perspective in regard to the plane of the orbit.

I have been looking for an old article I know I have buried someplace, 
that describes how to plot comet orbits on sheets of stiff paper, cut 
the pieces out, and assemble them to give a 3-D model of the orbit with 
respect to the Earth's orbit.  Basically consists of plotting the comet 
orbit (parabola or whatever) in its own plane... Possibly could do that 
with your favorite, Voyager software, make a printer file, and scale it 
to a nearly circular one for the Earth's orbit... ?  Just need to mark 
the points on the Earth's orbit diagram where the plane of the comet 
orbit intersects, to cut a slit to place the other sheet... with the 
proper inclination.

Of course, there are ways of plotting and visualizing the orbits on a 
computer screen, even being able to "rotate" and zoom the images, but I 
think nothing beats having the 3-D model right in your hands...

Maybe 3-D Stereolithography or Xero-printing (from the shops at 
Honeywell)?  haha

Here's a remark I didn't finish posting to A-observing, some short time 

I recall observing Comet IRAS-Araki-Alcock with my 8 inch Meade 2080 
with a SAC group out at Fessler's Ranch north of Phoenix...  Like 
Darrell mentioned, very rare to see anything with recognizable motion 
visually in the scope -- other than the occasional meteor or an airplane 

Nice animation of Saturn's rings you just posted ! I will be very 
interested in seeing this project progress, only wish I had gotten 
something similar started..
Keep posting that stuff!

Oh, BTW I have re-posted your neat image links to astro-imager friends 
John Sanford, Earl Wilson, and Ernie Williams in California, and Jim 
Vail in Maryland...
You probably know of John from the Orange County Astronomers, former 
photography instructor at Chapman College, formerly published the RTMC 
Proceedings and organized the OCA Astro-Imaging Seminars, now retired... 
John has been working hard on imaging Saturn and the comet under dark 
skies at his Starhome Observatory near Springerville, CA.
My WAA, SAS, RTMC and IOTA buddy Earl is still working at Owens Dry Lake 
(lives in Lone Pine, CA, about as dark as can be), Pres. of the China 
Lake Astronomy Club, but doesn't get a chance to do as much imaging as 
he'd like...
Ernie Williams you will recognize as the A/V Wizard in the Main Hall at 
RTMC - Camp Oakes... He lives and works in the central LA basin and also 
doesn't get to do very much imaging...
Jim Vail is our old SAC friend of years ago, nuclear engineer now 
working for the NRC in Washington, DC area. Lives in the Maryland 
suburbs NW near the Beltway (Gaithersburg area).  Has to go all the way 
to West Virginia for some dark skies....
All of these guys are at least semi-active in IOTA with analog astro 

Gene Lucas
Tom Polakis wrote:
> Darrell Spencer wrote:
>> minute past the background starfield.   I've never observed anything
>> natural outside our atmosphere with such drastic apparent motion.
> In 1983, I did almost zero observing thanks to college, but I did take a trip 
> out to the farm land to see Comet IRAS-Araki-Alcock at closest approach.  At 
> 5 million km, it was only one-tenth of the current distance to Comet Lulin.  
> If I remember correctly, it moved 45 degrees in a single night.  At 100x, it 
> was not difficult to see the comet move "in real time" against the star field.
> Regarding the orbital crossing event, I'd say that it has been occurring very 
> gradually over the past month, since the inclination of Comet Lulin's orbit 
> to the ecliptic is nearly nil.
> Tom  
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  • » [AZ-Observing] Re: Glimpse of Lulin; comet orbit model ?; Saturn animation, etc. - Gene A Lucas