Vol. 28 No. 9 June 1999 http://physics.weber.edu/oas/oas.html


THE JUNE MEETING

The June meeting of the Ogden Astronomical Society will be held at 7:30 p.m. this Thursday June 10, 1999 in the Ott Planetarium on the Weber State University Campus.

From the Prez:

I am pleased to announce that the June 10 meeting will feature Professor Bradley Carroll of the Weber State University Physics Department. Professor Carroll has many years of experience in the exotic aspects of astrophysics and will share some of his insights with us. The professor is an engaging speaker and uses an intriguing but laid-back approach in his method of teaching. I would like to encourage all members make a special effort to attend this event as a token of our appreciation for his effort and the possibility of insuring another visit sometime in the future.

Professor Carroll's topic is "The Mysterious Magnetars". Magnetars are neutron stars with ENORMOUS magnetic fields that can tell astronomers a lot about what neutron stars are like. Great stuff.

THE PRESIDENTS PARSEC

Greetings Earthlings;

Well, I get back from RTMC and find our Secretary/Editor (B. Tillotson) pushing the deadline for my contribution to the newsletter. With such short notice I just hope it meets the lofty standards already established.

First, a few notes on RTMC. It was a good crowd for a full moon weekend. About 1100 was the attendance I heard with OAS and SLAS contributing about a dozen to the throng. The weather was nice, dry and sunny, with the wind getting quite frisky on Friday and Saturday nights.

Most of the vendors were there, with Celestron and Orion being two of the major no-shows. I engaged in a lot of buying, selling and trading as I found much that interested me this year.

One of the events I found interesting was a discussion of a method for taking mirrors, ground and polished out to a sphere, and then forming a paraboloid with it by applying pressure to the back of the mirror, thereby bending it to the desired figure. Bill Kelly of SLAS pioneered this method a few years ago and the speaker gave him credit for it. Bill was there, contributing to the discussion. The various methods this guy experimented with produced mirrors 1/20th wave and better on 20 inch, f/4 mirrors. The results were so promising Sky and Telescope magazine will feature it in an up coming issue.

Some of the big names were at RTMC this year. I spent time with Al Naglar looking at a pine cone 100 yards away at 400x with one of his new 3mm Radians. You could see diffraction rings on the glistening sap on the pine cone. I waited in line with Richard Berry to look through a spectrohelioscope. Wayne Sumner and I spent some time with Peter Ceravolo discussing grinding compounds and methods of mirror testing. (Yes Jim, I did ask him about your HD and the slight grimace on his face indicated that it is still a work in progress. I told him you and I were anxious to look through it this summer and he said he would get to it).

Sunday night was the best night for observing. The temp was in the mid 40's clear and calm. I spent most of the time comparing images in my new binoviewer in the 10 inch Dob. with the images in Steve Dodds 10 inch reflecting binoculars.

The food at the cafeteria was bad and my dogs got really dirty but we really enjoyed RTMC .

the Prez


ANTELOPE ISLAND IN JUNE

This month's public star party at Antelope Island State Park is scheduled for Saturday June 19. Our guest speaker for the slide show will be Mr. Seth Jarvis from the Salt Lake City based Clark Foundation. Times are as before, dusk, but please try to be set up before that in order to minimize the maneuvering vehicles among the people. If you have questions, contact a member of your Executive Committee.


A SPECIAL STAR PARTY IN JUNE

The club has been asked to set up telescopes and describe the wonders of the sky to visitors at East Canyon State Park in Morgan County on Saturday June 26, 1999. The club is collecting a fee for this event so as many members as possible are asked to attend and demonstrate their celestial skills. Maps and directions will be given at the June 10 meeting but briefly, the park is accessed by taking I-84 east to the Morgan Exit, #103. Go through Morgan and then Porterville, through the sparse houses and on a couple of more miles to the park entrance. We will probably set up on the grassy area near the Entrance Station or in the parking area just inside the gate. If you have questions contact Bob Tillotson at: bob@skyplanner.com or call 773-8106.


OAS POTENTIAL FOR  $$$$$

Attention members:

OAS member, Wayne Sumner, has received a very large amount of fine diamond grinding compound that was donated to our club by his employer. The feed back we got at RTMC about this stuff is that it is useful for metal working applications on bearings and metal molds, lapidaries for polishing sapphires, and polishing gun parts. Someone said it is also used to polish dental work. This material comes in bottles mixed as a slurry and in syringes mixed as a paste. These are all unopened. There are 800 containers of this material so even at $5.00 a pop the club stands to gain substantially.

If anyone has information about a potential buyer or if you wish to have input about this, please contact me, the Prez, via e-mail, at nitesite@lgcy.com or Wayne Sumner at sumner@iomega.com .

Ron


MINUTES

OGDEN ASTRONOMICAL SOCIETY

May 13, 1999

The regular meeting of the Ogden Astronomical Society was called to order by club president Ron Vanderhule at 7:35 p.m. Ron displayed and described a Ronchi tester he devised for testing the mirrors he and the Grinding Group are producing. The mirror grinding group is moving ahead with their projects. Dave Dunn exhibited a black glass mirror blank he is working on.

Bob Tillotson described the mail the club has received in the past month and left it available to members to peruse.

There are three star party events upcoming. Antelope Island will be on May 22nd and the OAS may be asked to set up telescopes for Antelope Island's annual Moonlight Bike Ride on the 26th. Also, the ranger at East Canyon State Park is anxious for a star party by the lake sometime in June.

The issue of a fee for the OAS when asked to do a star party was discussed. The members expressed their thoughts that the club should not sell themselves short considering the effort and equipment being offered. A $100.00 fee for public star parties was settled upon.

John Sohl gave an update on the WSU Observatory project. The original site has been re-selected and the concrete structure is being ordered.

The subject of OAS membership cards was raised; "where are they"? Bob T. said he would see what could be done.

The meeting then shifted to the topic of the evening. The recent occultation of Aldebaran was observed and recorded by several members. First, a video made by Dave Miller and Bob Tillotson was run. Then Jim Seargeant's video made from a point just north of Dave and Bob's location was run. Finally a video made by Patrick Wiggins at the same location as Jim was shown. Jim and Patrick's videos showed the on and off effect as the star grazed the moon's limb.

Jim and Dave then discribed the systems they used to record the occultation.

Dave Butler discussed tours of Mona Kea observatory in Hawaii.

Jim Seargeant exhibited some of his CCD images he had taken over the past months.

The meeting adjourned to informal discussions at 9:20 p.m.

Bob Tillotson, Secretary


The following article was forwarded to The Star Diagonal by OAS member Mike Reinsch:

Universe Size Not So Clear?

Recent Measure May Not Be Accurate

By Paul Recer

The Associated Press

C H I C A G O, June 1 -- A new method of measuring distances to far galaxies casts doubt about the proclamation last week by NASA astronomers that they had determined the age and expansion rate of the universe.

A technique using a radio-telescope is a "golden ruler" for measuring cosmic distances and calls into question the conclusions announced by astronomers using the Hubble Space Telescope who were supported by the National Aeronautics and Space Administration, a researcher said Tuesday.

"Ours is a direct measurement, using geometry, and is independent of all other methods of determining cosmic distances," said Jim Herrnstein of the National Radio Astronomy Observatory. "It is the most precise distance ever measured to a remote galaxy."

Herrnstein presented his findings today at the national meeting of the American Astronomical Society.

Fairly Large Margin of Error

He said the new technique shows a 15 to 20 percent margin of error in the results announced last week by a NASA team led by Wendy Freedman of the Carnegie Institute of Washington. The NASA team using the space telescope said last week that it had successfully achieved the goal of  measuring within an uncertainty of only 10 percent the speed at which the universe is expanding, a value called the Hubble constant.

Based on its study, the team concluded that the universe is 12 to 13 billion years old and is expanding at an accelerating rate of 70 kilometers per second for every 3.3 million light years in distance from the Earth. Herrnstein said this calculation is off by 15 to 20 percent. He based his conclusion on the difference in calculated distance to a specific galaxy using his technique compared with the calculation method used by the NASA group.

Measuring Via 'Standard Candles'

Freedman and her group of 27 astronomers funded by NASA spent eight years measuring the distance to stars that pulsate in brightness at a known rate. Such stars, called Cepheids, are considered "standard candles" whose varying luminosity gives a gauge for their distance. But Herrnstein said the technique using Cepheids is far less accurate than his new method that directly measures the motion of gas around a galaxy. Herrnstein used a galaxy called NGC 4258 to establish what he called a "golden ruler" for measuring cosmic distances. NGC 4258 is surrounded by a rotating cloud of gas. Within this gas cloud is water vapor, which tends to amplify radio signals. This creates radio "hot spots" called masers.

Triangulating Via Masers

The orbital speed of masers between NGC 4258 and Earth was measured in 1994, and again every few months over the following three years. By determining the speed at which the masers were moving, the astronomers created a triangle with the first maser position at one angle, the latest position at a second angle, and the galaxy center at the third angle. Measuring the angles gives the distance.

"We can use plain old trigonometry to calculate the distance," said Lincoln Greenhill, a member of the Herrnstein team. "It is very simple and direct," said Herrnstein. "Most of us know enough math from high school to do the calculation." The distance to NGC 4258 was calculated at 23.5 million light years, with an accuracy to within 4 percent. This distance has been calculated using the Cepheid star technique at 27 to 29 million light years.

Are Assumed Values Worse?

Herrnstein said that the distance measure using Cepheid stars is based on a series of assumed values, such as the distance to the Large Magellanic Cloud, a galaxy neighbor to the Milky Way. These assumed values, said Herrnstein, have a greater margin of error than does the direct measuring technique he is using.

Freedman, who attended a news conference at which Herrnstein announced his results, said the new study provided "wonderful data," but she would like other measurements to be taken to confirm its accuracy. Also, she said the assumed values used in the Cepheid star technique have been verified by a number of researchers and she was "confident" of the results.

Freedman admitted, however, that uncertainties in her team's results still needed to be checked out.

Herrnstein conducted his study using the Very Long Baseline Array, which is a series of radio-telescope antennae that are scattered across the United States, from the Virgin Islands to Hawaii. The antennae operate as a single unit and are able to measure natural radio signals to an accuracy 500 times greater than the Hubble can measure visible light.

See SEARCHABCNEWS.com for more...

 


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