Prime Focus

IN THIS ISSUE

TVS presents

(Editor's Note: This information is excerpted from the abstract of Gibor Basri and Christopher Johns-Krull's article named below.)

Dr. Basri's latest analysis of the spetra of T Tauri stars (TTSs) concentrated on variations in the optical continuum veiling and the strong emission lines. By examining the spectra of DF Tauri, he and his research team sought to study the notion of magnetospheric accretion in TTSs. The data found in observations only partially supported this hypothesis.

In the Astrophysical Journal article "The Spectral
Varibility of the T Tauri Star DF Tauri", Dr. Basri notes the difficulty of using a snapshot spectrum to attempt to characterize the star as a whole. Because DF Tau was the inspiration for the original suggestion of TTSs magnetospheric accretion, the team is working to interpret the variations and correlations.

Red shifted absorbtion components and blue shifted absorbtions in H alpha suggest that wind reaching the stellar surface is related to accretion.

Club News Notes

The following speakers have committed to TVS for upcoming programs: April 18 Gibor Basri
Tauri Stars (See
) May 16 Jeff Moore
Galileo June 20 Jack Sales
Light Pollution and Dark Skies

Yosemite Update

The Yosemite Fund continues to seek donations for repair work following the January disaster. Gifts of any amount are welcome. Call (415) 434-1782 for more information.

Mount Wilson Summer Program

Eligible students considering a career in science or science teaching are encouraged to apply. Staff members and students will live and work on Mount Wilson, home of the 100-inch Hooker Telescope and many other astronomical instruments.

Students are granted time on the Snow Horizontal Solar Telescope and its associated grating spectrograph. They will make daytime and nighttime observations using a 7-inch diffraction-limited refractor, observe using a 24-inch reflector with CCD system, and the 60-inch telescope.

Tuition, room and board, for the two-week program is $1,375. Students are responsible for transportation to Burbank, CA. For more information contact Professor Joseph L. Snider, CUREA Director: joseph.l.snider@oberlin.edu

RTMC set for May 23-2 6

SJAA/Bay Area Swap Meet and Auction

Swap meet sales run from 12 noon through 3:00 pm. The room will be reconfigured for the auction, which begins at 4:00 pm. It usually runs about two hours.

Sellers will pay a 10 percent commission to SJA A with a cap of $50 for any single item. Sellers set their own prices and terms for sale items. No admission fees or table charges apply to the swap meet.

Auction items must be registered during the swap meet, and the deadline is 3:45 pm. All participants are asked to donate $1 to obtain an auction number that permits both selling and buying. A 10 percent commission is applied to all successful sales. Payments for auction purchases are accepted only at the close of the auction. A single payment made to/by SJA A will cover net of purchases and sales. Credit cards are not accepted. Commissions are tax deductable, and donations are welcome.

Board
Alane Alchorn
Dennis Beckley
Rich Combs
Rich Green
Russ Kirk
Dave Rodrigues
Debbie Scherrer
Al Smith
Dave Sworin
Jim Zumstein

Tri-Valley Stargazers
P.O. Box 2467
Livermore, CA 94551

What's up in April

April

2	Wed	Comet Hale-Bopp (C/1995 O1) 2° north of Gamma Andromedae. Look in evening and morning skies.
3	Thu	Jupiter 4° south of Moon.
5	Sat	Mercury at greatest eastern elongation (19°). Best evening apparition of year for northern latitudes.
		Excellent weekend for observing: No Moon until dawn.
		Galileo third flyby of Ganymede (3,06 5 km).
6	Sun	Daylight Saving Time begins (2:00 AM PST becomes 3:00 AM PDT).
7	Mon	New Moon 4:02 AM PDT.
		Comet Hale-Bopp 1.3° from M34 (mag 5.2 open cluster).
8	Tue	Mercury 6° north of Moon.
		Indian (Saka) New Year 191 8.
10	Thu	Aldebaran occulted by Moon 9:47 to 10:44 PM
		Comet Hale-Bopp 2° south of Algol.
12	Sat	Astronomy Day.
13	Sun	Asteroid 7 Iris (mag 9.5) at opposition.
14	Mon	First Quarter Moon 10:00 AM
15	Tue	Income taxes due.
		Burmese New Year 1359 (9:4 0:48 PM).
18	Fri	Tri-Valley Stargazers meeting 7:30 PM Unitarian Universalist Church in Livermore, 1893 N. Vasco Road, Livermore. (3/4 mile north of I-580).
		Mars 4° north of Moon.
19	Sat	San Jose Astronomy Association Swap Meet and Auction, Houge Park, San Jose. Opens at 12 noon.
21	Mon	TVS Planning Meeting 7:00 PM Round Table Pizza, 1540 First St., Livermore (in Orchard Supply/Longs/Safeway shopping center).
22	Tue	First day of Passover (Pesach).
		Full Moon 1:33 PM
29	Tue	Last Quarter Moon 7:37 PM
30	Wed	Jupiter 4° south of Moon.

May

2	Fri	Callisto eclipsed by Jupiter's shadow 3:18 AM PDT.
3	Sat	Excellent weekend for observing: No Moon until after 4 AM
4	Sun	Eta-Aquarid meteor shower. Best before dawn.
		Saturn occulted by Moon 6:55 to 8:01 AM
5	Mon	Cinco de Mayo (Battle of Puebla).
		Ganymede occulted by Jupiter 3:05 AM
6	Tue	New Moon 1:46 PM
7	Wed	Galileo fourth flyby of Ganymede (1,5 84 km).
8	Thu	Aldebaran 0.6° south of Moon (occulted in Eastern U.S.).
		Io eclipsed by Jupiter's shadow 3:12 AM
9	Fri	Islamic New Year 1418.

Some Springtime Deep-Sky Objects

Comet Comments

Ephemerides

46P/Wirtanen

Date (00UT) R.A. (2000)	Dec	El	Sky	Mag
04-02	03h41.9m	+22° 16'	46°	E	10.5
04-07	04h04.5m	+24° 10'	47°	E	10.6
04-12	04h27.6m	+25° 50'	47°	E	10.8
04-17	04h51.1m	+27° 16'	48°	E	10.9
04-22	05h14.8m	+28° 25'	48°	E	11.1
04-27	05h38.6m	+29° 17'	49°	E	11.3
05-02	06h02.5m	+29° 54'	49°	E	11.5
05-07	06h25.7m	+30° 14'	49°	E	11.7

81P/Wild 2

Date (00UT) R.A. (2000)	Dec	El	Sky	Mag
04-02	08h15.6m	+21° 43'	109 °	E	10.1
04-07	08h23.9m	+21° 28'	106 °	E	10.1
04-12	08h33.0m	+21° 07'	103 °	E	10.2
04-17	08h42.8m	+20° 41'	101 °	E	10.2
04-22	08h53.3m	+20° 09'	98°	E	10.2
04-27	09h04.2m	+19° 32'	96°	E	10.3
05-02	09h15.7m	+18° 50'	94°	E	10.3
05-07	09h27.4m	+18° 02'	92°	E	10.4

Comet Hale-Bopp continues to put on a spectacular display. The inner coma shows fountains and hoods while both the gas and dust tails are prominent. By late March the comet is well-placed in the evening sky and no longer visible the morning sky. The evening viewing "season" for Comet Hale-Bopp began with the partial lunar eclipse on March 23 and continues through the first week of May. Most comet watchers will have their last view of the comet as it slips southward in the western evening sky in early May. Many astronomy clubs are taking the time to show the comet to the public. Astronomy Day (April 12) provides an opportunity to show the comet and the crescent moon in the west, and a bright planet Mars in the east.

A few more faint comets have been discovered recently. Comet C/1996 R3 was found on plates taken last autumn. It will remain faint. Comet C/1997 D1 (Mueller) was found by Jean Mueller as she worked on the Second Palomar Sky Survey. It will be closest to the sun late this year (at 2.24 AU) and may then be visible in amateurs' scopes. Finally, the Spacewatch program on Kitt Peak picked up an object first believed to be an asteroid but now showing a coma. Comet C/1997 BA6 (Spacewatch) is presently 8.8 AU from the sun and won't reach perihelion (3.45 AU) until Dec. 1999, nearly three years away. The coma is showing a slight amount of activity, and it is possible that the comet will be visible in amateur instruments deep in the Southern Hemisphere in 1999.

Orbital Elements

Object	Hale-Bopp	P/Wirtanen	P/Wild 2
Peri. Date:	1997 04 01.13453	1997 03 14.14299	1997 05 06.62789
Peri. Dist (AU):	0.9141030 AU	1.0637469 AU	1.5826156 AU
Arg/Peri (2000):	130.59083 deg.	356.34322 deg.	041.77000 deg.
Asc. Node (2000):	282.47069 deg.	082.20387 deg.	136.15458 deg.
Incl (2000):	089.42936 deg.	011.72255 deg.	003.24276 deg.
Eccen:	0.9950969	0.6567490	0.5402220
Orbital Period:	~4700 years	5.46 years	6.39 years
Ref:	MPC 28052	MPC 27080	MPC 28272
Epoch:	1997 03 13	1997 03 13	1997 04 22
Absol. Mag "n":	-1.5/4.0	9.0/6.0	7.0/6.0

A Wasted Trip to The Dark Site?

Morning twilight comes upon us quickly, even more so it seems when you are doing astrophotography. I've been up to The Dark Site three times in eight days, once mid-week, to photograph Comet Hale-Bopp. In particular, I've been after a wide-field photo of the comet while it is in the vicinity of the North American Nebula (NGC7000 ). I felt that the combination of the comets, yellow dust tail and blue ion tail with the red emission of NGC7000 would make for a nice photo.

From casual discussions with club members, it seems most fail to make the pilgrimage to The Dark Site because "it's a long drive up that twisting and bumpy road." Factoring in the time it takes me to pack all of my gear and to assemble all of the necessary provisions for a cold night, it takes me about three hours to make the trip from Dublin. Thus, driving up during mid-week is challenging, particularly since the workday looms with the coming dawn.

While the drive up to The Dark Site is a bit long, it should be appreciated as part of the whole experience. Like other hobbyists, we have chosen an endeavor that enables us to put the tensions of everyday life behind us for a few hours. As we explore the night sky, we are continually challenged, as we wrestle with trying to understand our place in the universe. More palpably, on the ride up to The Dark Site, one can see first hand the interactions of the local ecosystem. The variety of life one experiences is wonderful. Most apparent are the grazing cows, that give you dumb looks as you drive by, and the horses.

Between dusk and dawn it is not uncommon to see deer and red-tail fox skittering across the road, climbing cliffs that you would swear would be inaccessible. Squirrels and chipmunks flash past in the blink of an eye, while racoons and skunks waddle by lasily. The magpies (?) are very bold as they peck away in the middle of the road, only flying off at the last instant. In time, one gains an appreciation for the life-cycle of various creatures. For example, tarantulas amble across the warm asphalt during their autumn mating season. Mice are perhaps the most industri ous creatures. During winter, they have been known to make their home within the tube of the club telescope. They set-up shop just adjacent to the mirror, keeping warm as it radiaties away the days ' warmth. On ocassion, they have made their nests

from strips of finely torn toilet paper that they have pilfered from the site facili ties. Among all this, one must not forget to take in the beautiful scenery.

With nature unfolding all around me, my goal, as I mentioned previously, was to photograph Hale-Bopp and NGC7000, a photograph requiring a 50mm lens. Hale-Bopp rises tail-first over the NE horizon, with the nucleus finally coming into sight at about 4am, thus giving the appearance that it is zooming away from Cygnus. The dust tail was most readily visible, but with averted vision the ion tail could be traced nearly 15 degrees, making its way almost to the summer Milky Way. During this first trip I managed about a half dozen photos with my zoom lens. Not knowing the ideal exposure time, I took pictures of various duration. Then twilight came upon me before I had time to switch to the 50mm lens.

My mid-week jaunt was a spur-of-the-moment trip, as the cloud cover did not clear until after 5pm. I devoted this session to capturing the wide-field shot I'd become obsessed with obtaining. Unfortunately, I was unable to obtain the film I wanted, so again the exposures were somewhat experimental. Based on previous experience with similar film I guess-timated the exposure duration, appropriately so I thought. Unfortunately, the red response of the film was weak, and in the final result the North American Nebula was somewhat understated.

My last opportunity to capture this favorable conjunction was the morning of 15 March. After I set up earlier in the evening, the clouds slowly obscurred Orion, Gemini, Leo, and finally Mars. When I awoke at 3am, the sky was in slightly better shape, with a clear region near the zenith. This didn't last long though, as waves of clouds took up residence.

As I sat looking east, hoping for the sky to clear, I was suddenly stunned by a tremendously bright flash from the north. As I insti nctively turned in this dir ection, the hills lit up like daylight, and shadows were cast everywhere like fleeting ghosts. As I continued to swing around, the intensity of the light varied widely, and the shadows danced about as the light from the incinerating meteor bounced among the various cloud decks. Finally, looking south, I locked on to the streaking meteor as it disti ntegrated into 2 or 3 pieces in a final flash of white/pink light. I had seen my first bollide! I never did get the photo I wanted, but I'm now convinced, more than ever, that there is no such thing as a wasted trip to The Dark Site.

Observatory director's report

The drive system for the 17.5 inch telescope is broken. It looks like we lost a couple of teeth on an internal gear in the 1/2 RPM timing motor which drives the scope. It runs for about 19 seconds then slips for a second, then repeats. If any member has a 0.5 RPM 115 Volt 60Hz CCW Synchron, Hurst, or similar timing motor they would like to donate, we would be happy to accept it. I have several similar motors myself, but 0.6 RPM is the closest I have. And 1 RPM is the closest I have seen so far for a new motor in a catalog. My current plan is to change the gearing of the telescope to use a 1 RPM motor. I have a 1 RPM motor but I don't have the right gears in my junk box, so I am looking around.

A second problem has surfaced with the telescope. Two of the connectors which secure the diagonal mirror spider vanes to the side of the tube have failed, apparently from too much pressure. Three of the spider vanes are still connected. The diagonal mirror now changes in position as the telescope points to different parts of the sky, messing up the collimation of the telescope. The diagonal also vibrates much more with only three spider vanes supporting it. I hope to have this fixed by the time this newletter is out. See the web pages for the latest status.

Since the new pier extension was added, the polar allignment of the telescope probably requires adjustment too, but the other problems above have prevented testing this so far.

Adding the pier extension (12") and sliding the telescope tube down in its cradle (6" ) allowed the removal of about 35 pounds of counterweights. The tube covers now fit better without the counterweights so the problems with mice getting into the telescope and building nests behind the primary mirr or should be over. The telescope can now be pointed lower in the sky without being blocked by the observatory walls. The telescope can now be pointed all the way down to the horizon in the south with only partial obstruction by the observatory wall. The telescope eyepiece now sits six inches higher off the observatory floor. My plan is to build a six inch tall raised floor around the telescope to return the ergonomics to the previous configuration.

Once again, we have had a problem when members of the general public were invited to visit the observatory (by well meaning members) but were not escorted. People just "showing up" at the Mines Road gate are a serious anoyance to the ranch personel. They do not have (and should not have) the combination to the first gate or a key to the second gate. They do not know where they should go, or that they are expected to pay $3. They do not know the rules about raising dust, etc. They will likely set the dogs barking, and people will be awakened if it is late. They will surely attract the attention of the people at the ranch who will have to spend time dealing with the situation. If this happens often enough, we may lose our access to this wonderful observing location.

If there are club members there observing that night, and they are willing (or feel obligated) to host the visitors, it is unlikely that the visitors will want to stay very long. So some member must interupt an observing session to drive down to the road, open and close the gates and drive back up. This responsibility will probably fall on the person who has the most convieniently parked car, regardless of the seriousness of his or her observing. The member must the n repark the car in the dark, inconviencing everyone up there.

So the bottom line is that it is very inconvienient for everyone involved.

Fremont Peak requests "before" photos

Ranger Rick Morales at Fremont Peak is requesting that members of the astronomy community share with him any recent photos (prints, slides, or CCD images) taken at Fremont Peak. Specifically, he needs views from the area around the 30-inch telescope: the southern horizon, looking almost due south toward the Soledad Prison, before the new facility came on line (around April 1996).

Rick's supervis or wants to talk with prison officials - on a State Department of Parks to State Department of Corrections basis - about the effect of their light pollution on astronomy at the Peak. She thinks that "before" photos will be persuasive in this effort.

What would be best is a wide angle shot (a 28mm to 50mm lens, or so) with a two to five minute exposure showing the relative lack of skyglow in that region before the new prison was built. Of course, she will use whatever we can provide, if the preferred photos are not available.

Surely, someone has taken a piggyback photo of the lower Scorpio region that would cover the old prison area. If we can get a good "before" shot, we will then duplicate the exposure time and other settings to create an equivalent "after" photo. Rick's supervisor will then use these to demonstrate to the prison officials the effect that their lights have had on the night sky from the Peak.

Please send your photos directly to:
Rick Morales
Fremont Peak Observatory Association P.O.
Box 787
San Juan Bautista CA 95045

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