Prime Focus

The newsletter of the Tri-Valley Stargazers September 1997.
Translated (roughly) from postscript into HTML for your browsing and downloading pleasure.

Under construction
Current renovations to the Sky Shack Observatory have uncovered... Just kidding. Actually this is a shot of The Caracol, believed to be an ancient observatory. It is located at Chichen Itza, a central Yucatan Mayan site. (Clive Ruggles photo, Leicester University, 1986)


September general meeting
Club news notes
Star parties
What's Up in September
Comet Comments
Membership application

TVS presents

What: Constellations and Cultures
When: September 19, 1997
Who: Alane Alchorn
Where: Unitarian Universalist Church in Livermore, 1893 N. Vasco Rd.

The modern plagues of light pollution and persistent industrial haze did not bedevil ancient astronomers. For them, the stars were eternal, predictable, and very visible. Familiar constellations, graced with compelling names we no longer recognize, wheeled seasonally in an orderly procession. Night after night. Year after year. Lifetime after lifetime.

Club member Alane Alchorn will discuss the ways in which constellations and asterisms have been recognized in different cultures.

Club News Notes

Public thanks to anonymous donor

A very generous member, who wishes to remain anonymous, has given the club a brand new copy of the Millennium Star Atlas . This extraordinary gift will be available on monthly loan through the library. As with our valuable telescopes, a $50 deposit will be required. The deposit check will be returned uncashed when the Atlas is returned. The entire club thanks this member for his or her wonderful gift.

ATM workshop to resume

by Rich Combs After much soul searching (a minute or two), I've decided it's time for another telescope making workshop. Tentative plans are to have an orientation meeting in mid-September, then I'll order the glass, and we will start grinding in late September or early October.

The goal will be for everyone to have a finished telescope by Christmas. We will meet twice a week on Monday and Wednesday evenings, with a few Saturday sessions to build the mounts. The object of the workshop is a complete working telescope of better-than-average quality. We will grind, polish and figure the mirrors, most likely 6" f/8 parabolas, and build Dobsoninan mounts for the Newtonian reflector optical assemblies. For each scope, the focuser, secondary mirror, eyepieces, and finders will be bought commercially.

The mirrors will be aluminized by a professional coater. Total cost will be around $300-350. If you are on a tight budget some corners can be cut. There is no registration fee for the class. We'll be meeting in Sunol from about 7-9 PM.

You're following in the footsteps of about 40 previous workshop graduates, and will benefit from what we have learned over the last five years.

The only prerequisite is perseverance. You will succeed, but it will take a commitment on your part. Successful mirrors have been made by 12 year olds, students, liquor store owners; why, I even had an astrophysicist make a successful telescope! If they can do it, so can you.

If you are interested, please e-mail me back, and I will send more details as they are available. Looking forward to hearing from you. My e-mail address is: My telephone number at home is: (510) 846-1906.

Observatory update
Sky Shack director Chuck Grant will be assembling a long-term plan for uses of the observatory. He is leading a committee of Dave Sworin, Chuck Vaughn, and himself that will be collecting input from all interested club members.

If you have opinions about the Dark Sky Site, its potential for new and expanded uses, or concerns about the club scope, contact Chuck via e-mail. Alternatively, you may address a letter to him and send it to: Tri-Valley Stargazers, Attention: Chuck Grant, P.O. Box 2467, Livermore, CA 94551.

A volunteer is also sought to revitalize the club's binocular telescope project. At present, the scope is sitting disassembled. Previous experience with binocular assemblies is not required. Contact Chuck Grant if you would like to help with this project.


Five new members joined our ranks last month. Please welcome Victor Sickinger, a student member, and Christopher Bailey, Weston Clark, and David and Alice Hollingsworth.

Treasurer's report
Checking account: $6,177.54
Money market: $1,215.59
CD: $3,167.22

President Dave Anderson (510) 661-4249
Secretary Bill Burnap (510 ) 449-4552
Vice President Chuck Grant (510) 449-1500
Treasurer Gene Nassar (510) 462-7843
Observatory Director Chuck Grant (510) 449-1500
Librarian Chris Cody (707) 747-6550
Eyes on the Skies BBS Mike Rushford http://www.hooked. net/~tvs/eyes/
Web Site
Editor Alane Alchorn (510) 455-9464 (510) 455-9466 fax
Meeting Location Unitarian Universalist Church in Livermore 1893 N. Vasco Rd. 3/4 mile north of I-580
Membership: 191

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

Star Parties

Star parties

September 6 Sycamore Grove Park Livermore 8:00 PM

September 20 Sky Shack Observatory and Dark Site Final open house for 1997. Meet at Mines and Tesla Roads at 6:00 PM

For information on these or any other star parties refer to the club website.

---- With the school year back in session, we expect to receive requests from teaches for star parties. Rich Green, school star party chair, has created an e-mail list of members to be notified with upcoming dates. If you wish to be added to his list, call him at (510) 449-2190 for his e-mail address.

Space permitting, school star party information will also be printed here each month.

What's Up in September

by Dave Anderson

September 1997
1 Mon Labor Day.
New Moon 4:52 PM PDT.
Partial solar eclipse in Australia.
Io transits Jupiter 12:43 to 3:01 AM; shadow transits 1:17 to 3:35 AM
Europa occulted by Jupiter 9:19 PM, reappears from eclipse 1:25 AM
Io occulted 9:57 PM, reappears from eclipse 12:49 AM
2 Tue Moon at farthest apogee of year (40 6,479 km).
Io transits Jupiter until 9:28 PM; shadow transits until 10:04 PM
3 Wed Europa's shadow transits Jupiter until 8:01 PM
Ganymede reappears from eclipse 9:15 PM
4 Thu Asteroid 1 Ceres (mag 7.7) at opposition.
Callisto's shadow transits Jupiter until 11:01 PM
5 Fri Venus 3° south of Moon and 1.9° north of Spica.
6 Sat Star party at Sycamore Grove Park (Livermore Park District) 8:00 PM (Wetmore Rd. entrance near Holmes St.).
Mars 5° south of Moon.
7 Sun Delta Cephei at maximum 10:19 PM Variable rises to mag. 3.5 from 4.4 in about 1.5 days. (Period is 5.366 341 days). Compare Zeta Cephei (mag. 3.35) and Epsilon Cephei (mag. 4.2).
8 Mon Ganymede's shadow eclipses Europa (partial; 99% light drop) 3:56 to 4:12 AM
Europa occulted by Jupiter 11:38 PM
Io occulted 11:43 PM to 2:44 AM
9 Tue First Quarter Moon 6:31 PM
Io transits Jupiter 8:56 to 11:14 PM; shadow transits 9:42 PM to 12:00 AM
10 Wed Europa transits Jupiter until 9:05 PM; shadow transits 7:45 to 10:36 PM
Io reappears from eclipse 9:13 PM
Ganymede reappears 1:16 AM
11 Thu Coptic New Year (171 5 in Egypt, 1991 in Ethiopia).
12 Fri Mars Global Surveyor inserted into orbit around Mars.
Callisto occulted by Jupiter 8:38 PM to 1:25 AM
13 Sat Jupiter 4° south of Moon.
16 Tue Full Moon ("Harvest Moon") 11:50 AM
Total lunar eclipse visible from Eastern Hemisphere.
Also second closest perigee of year (356,966 km). Expect high tides.
Mercury at greatest western elongation (18 °). Best morning apparition of year for northern latitudes.
Io occulted by Jupiter 1:29 AM
Europa occulted 1:59 AM
Io transits Jupiter 10:43 PM to 1:01 AM; shadow transits 11:37 PM to 1:55 AM
17 Wed Galileo flyby of Callisto (524 km).
Io occulted by Jupiter 7:56 PM, reappears from eclipse 11:08 PM
Europa transits 8:34 to 11:24 PM; shadow transits 10:21 PM to 1:11 AM
Ganymede occulted 9:57 PM to 1:35 AM, eclipsed 1 :38 AM
18 Thu Saturn 0.8° south of Moon (occulted in Los Angeles).
Space Shuttle Atlantis (STS-86) launch scheduled. (Mir docking mission.)
19 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).
20 Sat Open House at The Dark Site. Meet at the corner of Mines and Tesla Roads, Livermore, at 6:00 PM
21 Sun Aldebaran 0.3° south of Moon (occulted in Asia).
Mars Global Surveyor begins aerobraking.
22 Mon TVS Planning Meeting 7:00 PM Round Table Pizza, 1540 First St., Livermore (in Orchard Supply/Longs/Safeway shopping center).
Autumnal Equinox 4:56 PM
23 Tue Last Quarter Moon 6:35 AM
Delta Cephei at maximum 12:42 AM
24 Wed Io transits Jupiter 12:32 AM; shadow transits 1:33 AM
Io occulted by Jupiter 9:44 PM, reappears from eclipse 1:03 AM
Europa transits 10:55 PM to 1:45 AM; shadow transits 12:56 AM
Ganymede occulted 1:30 AM
25 Thu Io transits Jupiter 6:59 to 9:17 PM; shadow transits 8:02 to 10:19 PM
26 Fri Io reappears from eclipse 7:31 PM
Europa reappears from eclipse 10:38 PM
27 Sat Excellent weekend for observing: No Moon until 3:22 AM
Chi Cygni at maximum brightness (about 5.2, up from about 12 over an irregular period of about 407 days).
Asteroid 8 Flora (mag 8.1) at opposition.
28 Sun Ganymede's shadow transits Jupiter 7:48 to 11:26 PM
29 Mon Callisto eclipsed by Jupiter 10:29 PM

October 1997
1 Wed New Moon 9:51 AM PDT.
Io occulted by Jupiter 11:33 PM
Europa transits 1:19 AM
2 Thu Rosh Ha-Shanah (Jewish New Year 5758, at sunset 6:43 PM).

Some Early-Fall Deep-Sky Objects

M57 The Ring Nebula, a famous planetary nebula in Lyra.
M27 The Dumbbell Nebula, a superb planetary in Vulpecula!
NGC6960/92/95 The Veil Nebula in Cygnus. A large supernova remnant. (Try an OIII filter).
NGC7000 The North America Nebula near Deneb. Fine in binoculars under dark skies.
M15 Rich, compact globular cluster in Pegasus.
NGC7009 The Saturn Nebula, a bright planetary nebula in Aquarius.
NGC7293 The Helix Nebula, a large planetary nebula, also in Aquarius.
NGC7331 A large, bright spiral galaxy in Pegasus. Stephan's Quintet is nearby.
NGC7789 Very rich but faint open cluster in Cassiopeia.
M31, M32, M110 The Andromeda Galaxy (and companions)! Marvelous with any instrument, even unaided eye.
NGC7662 Blue Snowball planetary nebula in Andromeda, a bright annulus.

Comet Comments

By Don Machholtz


C/1995 O1 (Hale-Bopp)
Date (00 UT) R.A. (2000) Dec El Sky Mag
09-09 07h56.2m -28° 15' 58° M 5.6
09-14 07h59.5m -30° 19' 60° M 5.7
09-19 08h02.5m -32° 25' 63° M 5.8
09-24 08h05.1m -34° 31' 65° M 5.9
09-29 08h07.3m -36° 38' 68° M 6.0
10-04 08h08.9m -38° 46' 70° M 6.1

C/1997 N1 (Tabur)
Date (00 UT) R.A. (2000) Dec El Sky Mag
09-09 11h54.8m +32° 11' 29° E 9.5
09-14 12h26.3m +34° 47' 34° E 10.0
09-19 12h58.8m +36° 43' 39° E 10.5
09-24 13h31.6m +38° 00' 43° E 11.0
09-29 14h04.0m +38° 41' 47° E 11.4
10-04 14h35.5m +38° 52' 51° E 11.8

C/1997 O1 (Tilbrook)
Date (00 UT) R.A. (2000) Dec El Sky Mag
09-09 13h33.8m +04° 05' 36° E 11.9
09-14 13h39.7m +05° 16' 33° E 12.1
09-19 13h45.6m +06° 22' 30° E 12.2
09-24 13h51.4m +07° 24' 28° E 12.4
09-29 13h57.1m +08° 24' 26° E 12.6
10-04 14h02.8m +09° 23' 25° E 12.7

Another new comet has been discovered by a Southern Hemisphere observer. Mean while, Comet Hale-Bopp rolls into the morning southern sky for many North American observers. Comet Tabur (C/1 997 N1), which is behind the sun and will soon appear in our evening sky, has shown some diffuseness lately. This indicates that it may be fading out- only time will tell. Finally, three more comets have been found by the solar-orbiting SOHO satellite, bringing its total to twenty. None of these comets have been seen from the earth and most of them belong to the Kreutz Sungrazing Group.

Justin Tilbrook of Clare, South Australia used an 8-inch reflector to discover a new comet on July 22. It was in the evening sky, just north of the constellation Corvus, and magnitude ten. Comet Tilbrook (1997 O1) is presently receding from both the earth and the sun, and therefore growing dimmer.

Comet Hale-Bopp, as seen from the earth, is pulling away from the sun and moving south. This provides a limited opportunity for Northern Hemisphere observers to get their last look at the comet. From 25 Degrees North Latitude the comet will be seen best in mid-October when it will be 20 degrees above the southern horizon at morning twilight. This is why this is possible. In early September Comet Hale-Bopp is low in the southeast at astronomical twilight. With each passing morning it is higher in the sky at astronomical twilight; this is because it rises earlier each day while the sun rises later, giving the comet additional time to climb. After mid-October this daily gain begins to be offset by the comet's continued southern motion, and by the end of the year it will no longer be visible. A final encore presentation of the comet for those at 25 Degrees North Latitude occurs in early 1998 when the comet winds northward again, peeking over the southern horizon at evening twilight.

Observers further north will not be quite as lucky. At 40 Degrees North Latitude Comet Hale-Bopp will be best seen between mid-September and mid-October, when it will be rising above your ESE horizon at morning astronomical twilight. It will not get more than five degrees high in dark sky on any of these mornings. If you live between any of these aforementioned latitudes, you can probably figure out your own comet watching situation. In any event you'll need a low southeastern horizon, clear air and probably a medium-sized telescope to view the comet, which is about 300 million miles away.

Orbital Elements
Object: Hale-Bopp Tabur Tilbrook
Peri. Date: 1997 04 01.13800 1997 08 15.4779 1997 07 13.2599
Peri. Dist (AU): 0.9141405 AU 0.395469 AU 1.373622 AU
Arg/Peri (2000): 130.58915 deg. 344.2126 deg. 336.0222 deg.
Asc. Node (2000): 282.47069 deg. 147.6169 deg 231.1502 deg.
Incl (2000): 089.42943 deg. 085.9685 deg 115.8011 deg.
Eccen: 0.995 1172 1.0 1.0
Orbital Period: ~2500 years Long Period? Long Period?
Ref: MPC 295 68 MPC 302 44 IAU Cir. 670 7+
Epoch: 1997 06 01 1997 08 15 1997 07 13
Absol. Mag/"n": -1.0/4.0 10.0/ 4.0 8.0/4.0

Tri-Valley Stargazers Membership/Renewal Application
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