Vol. 29 No. 3 December 1999 http://physics.weber.edu/oas/oas.html

THE DECEMBER MEETING

The regular monthly meeting of the Ogden Astronomical Society will convene at 7:30 p.m. in the Ott Planetarium on the Weber State University campus this Thursday December 9, 1999. The Prez. has arranged another interesting High-Tech. Program for members.

We will explore the latest and most popular astronomy related internet web sites. OAS members are invited to arrange time to use the planetarium's computer to bring up and demonstrate their favorite site. You must first contact the Prez, Ron, at nitesite@lgcy.com or call 544-9458 to arrange time to demonstrate a site at this meeting.

THE PRESIDENT'S PARSEC

Greetings Earthlings,

Well it's the end of another millennium and we all know what that means. Everybody gets all retrospective about events and people that preceded. So, not to be out done, I'll offer up some of my own flashbacks from my brief but stellar career as an amateur astronomer.

I will begin with some personal milestones:

1) Sept. 1995: I Cashed in 2 1/2 paint buckets full of change to buy a new 16-inch Meade from a guy in Salt Lake who found out it would not fit in his car. ( off topic side note: a one gallon paint can will hold $395.00 in change ).

2) Oct. 1995: I took the new scope to my first star party at a jr. high school in Ogden. At last, I'm one of the guys. Although some still had reservations after a night of hearing me say " Hey kid, I got this bright thingie in the eyepiece. Wanna look"?

3) August 1996: First light with my first home made scope at Monte Cristo. Talk about apprehensive. "Oh no" I moaned as I focused the first object into view, " Vega has lines all across it". Jim Seargeant gently guides my limp body from the scope and peers into the eyepiece. " No, that's Jupiter in the field of view "he says assuredly," and it is a perfect image ". It was my most rewarding moment since completing potty training.

4) May 1996: My first trip to RTMC in Big Bear California was overwhelming. There were telescopes and eyepieces everywhere you looked. " Is this heaven ?" I asked some guy named Kinsella. He said he wasn't sure. I found out later that it snowed that weekend. Then, one evening, I encountered a vendor demonstrating his optics. From a special box, he removed a 2-inch, 32 mm, 88 degree field-of-view eyepiece that he was selling for $1100.00. He put the eyepiece into the focuser of a 6-inch rich field APO triplet refractor and in German invites me to take a look. The view was so huge so sharp and so real that I actually felt weightless the entire time I was looking.

5) September 1998, Cathedral Gorge Nevada: We wait until 4:00 a.m. to see the mother of all nebulas, M 42, in "Meter Mikes" 40 inch light bucket. I have described this event before, how you look "into" instead of "at" M 42 with a scope that size. I looked at it for several minutes before I realized that the reason it looked so different was all the color I could see. Seeing pink, green, and blue filaments is really impressive.

6) Elizabeth Ridge 1996: Deloy Pierce comes bustling through the bushes to the open trailer door where my wife and I are getting coffeed up and preparing for the night of viewing ahead. "You need to come see Jupiter" he announces breathlessly. By the tone of his voice I know something peculiar is happening but I play it cool. "I've seen Jupiter before" I reply calmly. "Not like this you haven't " he says. The cryptic gravity with which he utters the last statement energizes the moment. In an instant we are both waiting at Steve Dodds 20 inch Dob. It's barely twilight and the sky is a deep blue as we restlessly wait our turn at the eyepiece. As others step away from the eyepiece tears stream down their faces, their mouths are moving but their brain is incapable of supplying the correct and necessary verbiage to describe the apparition. (Sorry folks, I just got my literary license last week and I am still a little reckless).

Finally it is my turn. I look....there it is. Jupiter unveiled. Solid and unwavering. Distinct orange and brown bands transverse the disk and distinct white opals punctuate the many swirls. The view is too staggering. It must be a trick I thought. Turning abruptly I jump from the ladder and run the short distance to my telescope. Jerking open the lid of my eyepiece case I grab the 9mm Nagler and throw it into the focuser, all in one seemingly fluid motion. I point the instrument at the luminary above and look. Jupiter is framed in the field of view with all the glory it had in the 20 inch before. I step back and look at the side of my scope. I fully expected to see "Hubble" written on the side, but it still read "Meade". Moments later the tunnel through the atmosphere closed. It was a truly epic moment.

I was going to cover the best meetings and the best star parties that OAS has had since I have been there but I think I have pushed the tolerance barrier again so I will do those in the next newsletter, (if I'm up to it ). Hope you can all sleep until then.

the Prez

DETECTION OF A SATELLITE ORBITING THE NUCLEUS OF COMET HALE-BOPP

Z. Sekanina: Detection of a satellite orbiting the nucleus of comet Hale-Bopp (C/1995 O1). EARTH MOON AND PLANETS, 1999, Vol.77, No.3, pp.155-163

CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA,91125

This paper reports on the detection of a satellite around the principal nucleus of comet Hale-Bopp. As shown elsewhere, a successful morphological model for the comet's dust coma necessitates the postulation of overlapping jet activity from a comet pair. The satellite has been detected digitally on images taken with the Hubble Space Telescope's Wide Field Planetary Camera 2 in the planetary mode on five days in May-October 1996. An average satellite-to-primary signal ratio is 0.21 +/- 0.03, which implies that the satellite is similar to 30 km in diameter, assuming the main nucleus is similar to 70 km across. To avoid collision, the separation distance must exceed 50-60 km at all times. The satellite's projected distances on the images vary from 160 to 210 km, or 0.06 to 0.10 arcsec. The satellite was not detected in October 1995, presumably because of its subpixel separation from the primary. The radius of the gravitational sphere of action of the principal nucleus 70 km in diameter is 370-540 km at perihelion, increasing linearly with the Sun's distance: the satellite appears to be in a fairly stable orbit. Its orbital period at similar to 180 km is expected to be similar to 2-3 days, much shorter than the intervals between the HST observations. If the main nucleus should be no more than 42 km across, Weaver et al.'s upper limit, the satellite's orbit could become unstable, with the object drifting away from the main nucleus after perihelion. Potentially relevant ground-based detection's of close companions are reported. Efforts to determine the satellite's orbit and the total mass of the system will get under way in the near future. Copyright 1999, Institute for Scientific Information Inc.

On the internet at HTTP://www.sfsm.org

MINUTES

OGDEN ASTRONOMICAL SOCIETY

November 11, 1999

The regular meeting of the Ogden Astronomical Society was called to order by club president Ron Vanderhule at 7:35 p.m. Bob Tillotson informed members who ordered Kalmbach Publishing wall calendars for year 2000 that the order is in and he can distribute the calendars after the meeting. Also, Bob has free samples of The Sky Planner.

Mr. Steve Vought will speak tomorrow evening, Nov. 12, here at the Lind Lecture Hall at WSU. John Sohl updated the members on the progress of the WSU Observatory; the concrete pads are being poured, doors on the building are being hung, the electrical power is being installed. John and Sheri distributed the mini LED lights to members who had ordered them.

Mr. Art Easonberg from the Hansen Planetarium was introduced. He is now administering the Project Astro Utah program. A call for more astronomers was made.

The evening's program was introduced. Three popular software programs were demonstrated; Red Shift, The Sky and Starry Night.

The meeting adjourned at 9:45 p.m.

Bob Tillotson, Secretary

NOTICE: OAS members who ordered Desk Calendars from Alan Jensen will be able to pick them up at the December 9 meeting. They Have Arrived...

Jim Seargeant's - Images

(Click on the image to get the original larger version.)

Uranus and Moons

This is a composite of three CCD images of Uranus and it's brightest moons taken on 13, 14, and 15, November 1999. The last image was taken with the help of two of Adam Johnstons students, Jami and Pam. The three images were registered and combined into one so that the two bright stars in the right were exactly overlapped, showing the motion of the planet and it's moons over those three days. The difference in apparent size of Uranus is caused by differences in the seeing conditions on each of the nights. The seeing was at it's best on 14 Nov and allowed the sharpest image.

This picture is shown in negative form - black stars on a white sky - in and attempt to make some of the small, dim moons visible. The deep black of the stars, white of the sky, and rough edges on the stars are the result of extreme processing measures, also done in an attempt to produce a easily printable picture.

The motion of some of Uranus' brightest moons are apparent here. Like those of Jupiter and Saturn, the moons of Uranus do a frantic dance in the giant planet's powerful gravity well and it's hard to keep track of shech is which. The labels above are a best guess. None of my software shows the moons of Uranus, but I found a NASA web site that provided a Uranus moon tracker at the following URL:

http://ringside.arc.nasa.gov/www/tools/tracker2_ura.html

However, the site's tracker, which showed distances from Uranus' center to each moon over a period of time, and the viewer, which showed a graphic of the Uranus's moons and rings at a specific time, did not agree. The positions of the moons shown by the viewer did not agree at all with what are shown in the pictures, so I went with the information the tracker provided. Still, there is ambiguity as to which moon is which. The middle picture shows four moons. The others may have shown more that are lost in the glare of the planet.

These shots were taken with my 12" Meade operating at f/10. I took some care with collimation and focus, which are vital in getting sharp planetary images. Focus, for instance, changes as the Meade's aluminum tube cools with the night, so I checked focus just before each image sequence. Each day's picture was the result of combining several short, .11 sec. exposures. The short exposures were necessary to freeze atmospheric turbulence that is death for high resolution imaging. I would have liked to use my adaptive optics unit to combat turbulence, but no guide stars were in the necessary position. For each final image, five to ten short exposures were taken, the worst of each series discarded, bias was subtracted, and each series was median combined to form one image. With the short exposures, there is really not much signal to work with; next time I will take many more in each series so that some of the images can be added together instead of averaged. Many of the techniques I (attempt to) use in this sort of imaging are from Thierry Legault, author of an article on high resolution imaging in the Jan. 2K Sky & Tel.

To give an idea of the scale of this image and the amount of motion from day to day, the two bright stars in the right of the frame are, according to TheSky, 2' 52" apart. The magnitude of the star on the upper right is 13.08. Uranus' magnitude is listed at 5.82.

Jim Seargeant