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 back... 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 video... Cheers, Gene Lucas (17250) 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 -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.