Stockton Astronomical Society
Valley Skies - April 2004 Issue
For many years, the Stockton Astronomical Society has done nothing special for Astronomy Day, the day designated annually by the Astronomical League and the Astronomical Association of Northern California for public outreach. This year will be different.
Two years ago, Becky and Gary Greider arranged a Lodi Star Party, sponsored by the Lodi News-Sentinel. SAS volunteers were there, at Hutchins Street Square, with ten telescopes. Hundreds of Lodi residents enjoyed the stars that night. Many expressed the hope that we'd do it again.
Becky and Gary have been working to get another Lodi Star Party set up, this time in a darker location - Micke Grove Park. - on Saturday, April 24. That is the day designated by the AL and the AANC as Astronomy Day. And since we have been bumped from the Shima 2 parking lot for Sky Tours on Friday 23rd (by shuttle buses for the Asparagus Festival), we decided to broaden the scope of the Saturday night star party in Micke Grove.
So this will be our Astronomy Day Star Party for residents of Lodi and Stockton. We will publicize the event throughout the area...and hope for a dark, clear sky. We'll start in twilight at 8:00 p.m. and go till at least 10:00 p.m.- later if the crowd lingers.
We'll have an area near the Historical Museum, with room for plenty of telescopes. We'll have an area set aside for star talks, using a green laser to point out constellations. Park staff will have refreshments available and the SAS will have an information table for anyone interested in membership. There will be no admission charge to the park that evening.
Our primary need, obviously, is volunteers with telescopes. Bernie Knoll will bring his 18" Dobsonian from Coulterville to be part of this evening under the stars.
For most of you, this is much closer to home. Can we count on you too? Please call or e-mail to let us know:
Becky Greider: 333-1515; Jerry Hyatt: 474-0159; Trevor: 478-4380
by SAS member Glen Youman
In the February 2004 issue, Glen discussed telescope mounts, and stressed the need for a solid foundation for a telescope used for astrophotography. In the March issue he discussed the intricacies of Guiding and a primer on film for astrophotography. In this final segment, Glen answers a number of Frequently Asked Questions to help you get started on the right foot.
Part III - "The above is all well and good but how do I utilize my existing equipment for imaging?"
Frequently Asked Questions -
Q1: I have a fork-mounted SCT, what do I need to do to take film based astrophotos?
A: Tune the mount. This involves replacing any bushed bearings with ball/roller bearings. Adjust the worm drive to eliminate as much backlash as possible, adjust the Dec/Alt. drive to eliminate as much backlash as possible. Balance the scope so that there is a slight unbalance (a dichotomy) in both the RA/AZ and DEC/ALT direction. You want the drive to lift the scope in the direction of travel to lessen the effects of gear backlash.
Consider locking the mirror in place and adding an OEM focuser to the back of the SCT. This eliminates mirror shift but also limits the use of the scope to imaging unless you have sufficient back focus to allow both imaging and visual use.
Purchase an off-axis guide device and an adjustable guide eyepiece with illuminated cross hairs (be aware of the amount of back focus you have available).
If using the scope in the ALT/AZ mode purchase a field de-rotator (do you have enough back focus?).
If tripod mounted, consider a well-built solid leg wooden tripod; you will experience less tripod-induced vibration than with an aluminum tube adjustable tripod.
[Disclaimer - The last time I used a fork mounted SCT for imaging was in 1979 so I may have missed some important points in the above answer.]
Q2: Same question as Q1 but I want to do CCD imaging.
A: Same answer except eliminate the off-axis guide if your CCD camera is equipped with a separated guide chip. Use an electronically controlled OEM focuser.
Consider the use of the adaptive optics add-on if using an SBIG CCD camera. SBIG's AO-7 unit will eliminate many of the problems with mirror-shift and gear backlash and will make a fork-mounted unit equal to a high-end mount. In addition, use of the AO-7 will result in reduced star bloat resulting in tighter (smaller) star images.
Q3: I wish to use my Dobsonian for imaging, what do I need to do?
A: Replace the friction bearings with roller bearings and install a drive system for both axes. Install a field de-rotator. (Andy Saulietis is the person to contact for this type of modifications).
See Mel Bartel's website for information on computer control of a DOB.
Fabricate and install an adjustable balance system. (See also the answers to Q1 and Q2 above.)
Q4: I have an equatorial mounted scope, what do I need to do in order to image?
A: If the OTA is an SCT, the answers to Q1 and Q2 apply with the exception of the field de-rotator.
If using a refractor, consider the use of a separate guide scope. The answers to Q1 and Q2 also apply with the exception of a mirror lock down and the de-rotator.
Q5: Do I need goto capability to do imaging?
A: No. However, if doing CCD imaging (small field of view), you will find that a good planetarium program (Skymap Pro, Starry Sky, etc.) will be very useful in centering the object on the chip.
Goto capability, once mastered, is very useful in locating objects for imaging and would probably save valuable imaging time. I estimate I save at least an hour in a 5-6 hour imaging session by utilizing goto capability.
Q6: What is your imaging set-up?
A: A 128 mm F8 APO on a pier-mounted NJP-160 German equatorial mount equipped with semi-goto FS-2 drive system. I have a reducer that gets my scope to F6 for wider field images and a tele-extender that gives me f12 to f24 capability.
I have Robo-Focus installed on my focuser for computer control of the focus process. I have an SBIG dual-chip ST-10XME CCD camera with a five-position filter wheel (typically with Clear, Red, Green, Blue and H-alpha filters installed).
I have a separate 80 mm f9 achromatic guide scope equipped with an SBIG ST-4 auto-guider. The guide scope is mounted in adjustable scope rings in line with the main scope.
Software Bisque's CCDSoft V5 is used for camera control and image acquisition.
I use AIP4WIN (Berry and Burnell - Wilmann Bell) for image processing and assembly with final image adjustment using Photoshop.
Other sources of information:
Books are written about almost every aspect of astro-imaging. This article touches on only the basics.
The most valuable source that would aid you in making decisions about imaging needs and methods is probably the Internet. Locate astro-imagers on the net and look at their methods, equipment and results and, if necessary, contact them for additional information. I know that there are imagers who have experienced the full range of problems and have solved those problems. They will probably be happy to help you solve yours.
Don't be afraid to ask questions.
Please feel free to contact me for additional information (firstname.lastname@example.org, www.astrophotos.net).
The Science Directorate at NASA's Marshall Space Flight Center sponsors the Science@NASA web sites. The mission of Science@NASA is to help the public understand how exciting NASA research is and to help NASA scientists fulfill their outreach responsibilities.
Astronomers have discovered a mysterious planet-like body in the distant reaches of the solar system.
March 15, 2004: NASA-funded researchers have discovered the most distant object orbiting the sun. Its a mysterious planet-like body three times farther from Earth than Pluto. "The sun appears so small from that distance that you could completely block it out with the head of a pin," said Dr. Mike Brown, California Institute of Technology (Caltech), Pasadena, Calif., associate professor of planetary astronomy and leader of the research team. The object, called Sedna for the Inuit goddess of the ocean, is 13 billion kilometers (8 billion miles) away, in the farthest reaches of the solar system.
An artist's rendition shows the newly discovered planet-like object, dubbed "Sedna", in relation to other bodies in the Solar System, including Earth and its Moon, Pluto, and Quaoar.
This is likely the first detection of the long-hypothesized "Oort cloud," a faraway repository of small icy bodies that supplies the comets that streak by Earth. Other notable features of Sedna include its size and reddish color. After Mars, it is the second reddest object in the solar system. It is estimated Sedna is approximately three-fourths the size of Pluto. Sedna is likely the largest object found in the solar system since Pluto was discovered in 1930. Brown, along with Drs. Chad Trujillo of the Gemini Observatory, Hawaii, and David Rabinowitz of Yale University, New Haven, Conn., found the planet-like object, or planetoid, on Nov. 14, 2003. The researchers used the 48-inch Samuel Oschin Telescope at Caltech's Palomar Observatory near San Diego. Within days, telescopes in Chile, Spain, Arizona and Hawaii observed the object. NASA's new Spitzer Space Telescope also looked for it. Sedna is extremely far from the sun, in the coldest known region of our solar system, where temperatures never rise above minus 240 degrees Celsius (minus 400 degrees Fahrenheit). The planetoid is usually even colder, because it approaches the sun only briefly during its 10,500- year solar orbit. At its most distant, Sedna is 130 billion kilometers (84 billion miles) from the sun, which is 900 times Earth's solar distance. Scientists used the fact that even the Spitzer telescope was unable to detect the heat of the extremely distant, cold object to determine it must be less than 1,700 kilometers (about 1,000 miles) in diameter, which is smaller than Pluto. By combining available data, Brown estimated Sedna's size at about halfway between Pluto and Quaoar, a smaller planetoid discovered by the same team in 2002.
Sedna lies farther from the sun than Pluto.
The elliptical orbit of Sedna is unlike anything previously seen by astronomers. It resembles the orbits of objects predicted to lie in the hypothetical Oort cloud--a distant reservoir of comets. But Sedna is 10 times closer than the predicted distance of the Oort cloud. Brown speculated that this "inner Oort cloud" might have been formed billions of years ago when a rogue star passed by the sun, nudging some of the comet-like bodies inward.
"The star would have been close enough to be brighter than the full moon, and it would have been visible in the daytime sky for 20,000 years," Brown explained. Worse, it would have dislodged comets farther out in the Oort cloud, leading to an intense comet shower that could have wiped out some or all forms of life that existed on Earth at the time.
This is what Sedna looks like through the Palomar Observatory's 48-inch telescope. The dim object caught the attention of astronomers because it was moving, slightly, across the starry field.
Rabinowitz said there is indirect evidence that Sedna may have a moon. The researchers hope to check this possibility with NASA's Hubble Space Telescope. Trujillo has begun to examine the object's surface with one of the world's largest optical/infrared telescopes, the 8-meter (26- foot) Frederick C. Gillett Gemini Telescope on Mauna Kea, Hawaii. "We still don't understand what is on the surface of this body. It is nothing like what we would have predicted or what we can explain," he said.
Sedna will come closer to Earth in the years ahead, but even at closest approach, about 72 years from now, Sedna is very far away-farther than Pluto. Then it will begin its 10,500-year trip back to the far reaches of the solar system. "The last time Sedna was this close to the sun, Earth was just coming out of the last ice age. The next time it comes back, the world might again be a completely different place," Brown said.
by Patrick L. Barry and Tony Phillips
Probes that can distinguish between "interesting" things and "boring" things are vital for deep space exploration, say JPL scientists.
Along with his colleagues in NASA's Space Technology 6 Project (ST6), JPL's Steven Chien is working to develop an artificial intelligence technology that does just that. They call it the Autonomous Sciencecraft Experiment, and it's one of many next-generation satellite technologies emerging from NASA's New Millennium Program.
The Autonomous Sciencecraft technology that will be tested as part of NASA's Space Technology 6 mission will use artificial intelligence to select and transmit only the scientifically significant images.
As humanity expands its exploration of the outer solar system-or even neighboring solar systems!-the probes we send suffer from two unavoidable handicaps. First, commands radioed by mission scientists on Earth take a long time to reach the probe: six hours for the planned New Horizons mission to Pluto, for example.
Second, the great distance also means that data beamed back by the probe trickles to Earth at a lower bandwidth-often much less than an old 28.8 kbps modem. Waiting for hundreds or thousands of multi-megabyte scientific images to download could take weeks. And often many of those images will be "boring", that is, they won't contain anything new or important for scientists to puzzle over. That's certainly not the most efficient way of using a multi-million dollar probe.
Even worse, what if one of those images showed something extremely "interesting"-a rare event like a volcanic eruption or an unexpected feature like glaciers of methane ice? By the time scientists see the images, hours or days would have passed, and it may be too late to tell the probe to take a closer look.
But how can a probe's computer brain possibly decide what's "interesting" to scientists and what's not?
"What you really want is a probe that can identify changes or unique features and focus on those things on its own, rather than just taking images indiscriminately," says Arthur Chmielewski, one of Chien's colleagues at JPL.
Indeed, that's what Chien's software does. It looks for things that change. A mission to Jupiter's icy moon Europa, for instance, might zero in on newly-formed cracks in the ice. Using artificial intelligence to set priorities, the probe could capture a complete movie of growing fractures rather than a single haphazard snapshot.
Until scientists can actually travel to deep space and explore distant worlds in person, they'll need spacecraft "out there" that can do some of the thinking for them. Sciencecraft is leading the way.
Learn more about Sciencecraft at nmp.nasa.gov/st6. Kids can make a "Star Finder" for this month and learn about another of the ST6 technologies at spaceplace.nasa.gov/st6starfinder/st6starfinder.htm.
This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Saturday, April 24 -- Astronomy Day Star Party
at the County Historical Museum in Micke Grove Park
Although Mercury will have left the evening sky, Venus and Mars (in Taurus), Saturn (in Gemini) and Jupiter (in Leo) will provide choice planetary viewing. With its rings still tilted at more than 25 from edge-on, and still high in the western sky around 9 pm, Saturn remains the showpiece of the evening. However, Jupiter and its moons will be high overhead, providing good viewing throughout the session.
8:00 to 10:00 pm in Micke Grove Park
Desert Sunset Star Party
May 13-16, 2004
The 2004 Desert Sunset Star Party will be held at the Caballo Loco Ranch, about 11.5 miles south of Three Points, AZ, on Rt. 286, and then east for 8 miles. This RV ranch is in a secluded area of Arizona with dark skies. The telescopes of Kitt Peak are in clear view to the west.
The DSSP begins on Thursday night May 13 and runs through Saturday night. We will have a speaker on both Friday and Saturday evenings along with door prize giveaways. Registration information will be posted on the DSSP website: chartmarker.tripod.com/sunset.htm
Pat and Arleen Heimann
Shingletown Star Party 2004
June 16 through June 20, 2004
(Star party closes June 21, 2004)
This is the SSP's third year. It offers some of California's darkest skies and convenient easy-highway access. The star party is held on the runway of a closed airport, so there's no dirt or tumbleweeds on the setup field.
This years SSP is adding a shower truck and ice truck to its list of amenities. Just a few miles away is the resort community of Shingletown which provides full services. Beautiful Mount Lassen National Volcanic Park is 17 miles up the mountain.
Registration Now Open -- (Registration this year is limited to 300 attendees)
Find SSP 2004 at www.shingletownstarparty.org
SJAA Auction XXIV
Sunday, April 4, 2004
Houge Park in San Jose
It's spring, and time for the annual migration of astronomical paraphernalia from one garage to another! The San Jose Astronomical Association's annual auction is a great opportunity for beginners to purchase their first telescope at a great price! More experienced observers often find equipment they need for their next observing project, from OIII filters to finders to star charts.
Kevin Medlock will be our auctioneer.
Doors open at to register material for the auction, and view the auction material. The auction will begin at 1 p.m. and will run as long as needed. A seller may specify a minimum bid which, if not met, will return the item back to the seller with no commission applied. After the auction, buyers and sellers settle up using one check to (or from) SJAA and claim their items. Seller pays 10% commission, with a cap of $50 for any one item. We do not handle charge cards. There is no fee for bidder cards.
After the auction, material for the swap meet will be allowed into the hall, about 3 p.m. Sellers are encouraged to bring items that would interest the astronomical audience such as astronomical, science, computer, or tech items. The SJAA reserves the right to turn away inappropriate items for the swap. Joe Sunseri of Earth and Sky Adventure Products will be there with many fine new and used items. At the swap, each buyer pays the seller. Sellers are to keep track of their sales, and pay a 10% commission, as for the auction.
There are no table fees. All commissions from the auction and the swap are tax-deductible, as SJAA is a 501(c)(3) educational organization.
Do you have a large item such as a telescope? Please email the auction team at email@example.com with a description of the scope and a picture if possible. We will add it to the auction website for some pre-auction publicity.
For more about SJAA, visit our web site at http://www.sjaa.net or email Jim Van Nuland at the above address. See you there!
From Hwy. 17, take the Camden Avenue exit. Go east 0.4 miles, and turn right at the light, onto Bascom Avenue. At the next light, turn left onto Woodard Road. At the first stop sign, turn right onto Twilight Drive. Go three blocks, cross Sunrise Drive, then turn left into the park.
From Hwy. 85, take the Bascom Avenue exit. Go north about 0.2 miles; turn right at the first traffic light, onto White Oaks Road. At the first stop sign (another 0.2), turn left onto Twilight Drive. You will now be passing the park. Turn right at the first driveway, into the parking lot.
Attend a Conjunction!
is coming to the San Francisco Bay Area
July 20-24, 2004
Here's a conjunction you can actually attend-not just observe: a truly once-in-a-lifetime conjunction of the Astronomical League, the American Association of Variable Star Observers, the Association of Lunar and Planetary Observers, and the Astronomical Society of the Pacific.
Visit the website for complete details,
including secure on-line registration and payment
Co-hosted by the Astronomical Association of Northern California,
the Eastbay Astronomical Society,
and the San Jose Astronomical Association
Don't miss the
Astronomy Day Star Party
Saturday, April 24, 2004
8:00 P.M. - 10:00 P.M.
Micke Grove Historical Museum
FREE EVENT! FREE PARKING!
The Lodi News
Sentinel's Learning Link Department (Newspapers-in-Education)
Stockton Astronomical Society
County Office of Education
Copyright © 2004 by Stockton Astronomical Society
Last Updated: 4/2/2004