The regular meeting of the Ogden Astronomical Society will be held this Thursday February 12, 1998 at 7:30 p.m. in the Ott Planetarium on the Weber State University campus.

The main topic for this month's meeting will focus on the recently launched Lunar Prospector probe. Todd Pottorff, an OAS member since 1992 and an engineer for Thiokol, will discuss Thiokol's part in the launch vehicle. He plans to also show a video on the Prospector mission.

Membership cards, recently printed, will be available for members to pick up at the February meeting.

Folks who didn't get the opportunity, or did not take the opportunity, to purchase club shirts and caps last month will be able to do so in February. See Doug.

Several OAS members have begun their rolls in the project ASTRO-Utah. Those members will share their experiences, to date, with this new program.

Winter viewing doesn't have to be an endurance test or teeth chattering experience. Here are a few things that I use to help make for a more enjoyable night.

Dress in layers, long johns, then a flannel shirt, heavy pants, coat, moon boots or heavy shoes. Those snow mobile suits are useful too. A ski mask is good. Cover your head. You lose about ten percent of your body heat through your head. Make sure to cover your ears. Fingerless gloves let you Handle eyepieces without taking the gloves off. I like those little hand warmers you can get in sporting good stores to keep your fingers warm. I try to use a piece of carpet to stand on. This helps keep my feet warmer than standing on bare cement (not bare footed). A thermos of HOT what-ever you like. Don't breath on the eyepiece (DUH!) I have a hard time cleaning them off after that.

Give the telescope plenty of time to cool down if its been in the house. Keep it covered also so frost won't form on it later as it cools down. This might take hours when the temperature is very low.

A little planing ahead came make winter star watching enjoyable, (well, not miserable). Some of the best sights are in the winter skies so be sure to give them a chance.
 

Steve

What does one do with their telescope once you get past the "sight-seeing" phase? Contribute to astronomical research by observing variable stars. The tools are a notebook and a clock.

Through the generosity of long time variable star observer Ron Ham, the University of Denver has hundreds of charts and will provide interested observers along with complete instructions.

To give it a try, e-mail to: rstencel@du.edu with your name, mailing address and the constellation of your choice. You can also mail for information by writing to:

This effort is sponsored in part by the MARS region of the Astronomical League and the AAVSO.
 

President Steve Peterson opened the meeting at 7:30 p.m. Steve announced that club shirts and caps were available. A few minutes was allowed for members to be the first to but articles. Bob Tillotson and Doug Say oversaw.

The meeting was an Open House display of OAS member's projects. Scale models, mirrors and telescopes created by members were displayed.

Following the meeting, members expressed interest in holding such show and tell programs several times a year.

Meeting adjourned at 9:35 p.m.

The club has received registration information for the annual Oregon Star Party. Fliers will be available at the February 12 meeting. For quick access, their web address is:

Information for the Riverside Telescope Makers Conference (RTMC) can be found at:

The access fee to Antelope Island State Park has been raised to $7.00 per car.

[1964: U.S. military navigation satellite carrying two pounds of plutonium plunges to Earth. The radioisotope thermoelectric generator, or RTG, burns up in atmosphere as designed, releasing radioactive material. RTG is redesigned....1968: The NIMBUS-B U.S. weather satellite carrying six pounds of plutonium crashes into the Pacific Ocean off California coast shortly after liftoff. Both RTG's are retrieved intact, reinforced and re-flown....1970: Apollo 13 lunar lander carrying eight pounds of plutonium is discarded prior to crew's return from aborted moon mission. RTG sinks in the South Pacific near Fiji. Still there and believed intact....1978: Soviet spy satellite launched four months earlier with nuclear reactor containing 100 pounds of uranium plunges through atmosphere over Canada's Northwest Territories. Most burns up, but some survives. Cleanup lasts weeks....1996: Russian Mars probe plunges through atmosphere soon after launch. Its half pound of plutonium supposedly lands in Pacific Ocean, Chile or Bolivia. Plutonium unit not yet found.]

Cassini uses three RTG's, each containing about 24 pounds of plutonium. These are not small nuclear power plants. The heat generated from radioactive decay is changed into electricity by solid-state thermoelectric converters to provide the necessary power for the onboard computers and equipment. This is not the same reaction that occurs in nuclear fission power plants.

We've been using RTG's for about thirty years. Within this time period, three out of the 26 U.S. space missions using RTG's have failed. The failures have not been with the RTG's themselves, but have occurred due to problems with the launch vehicles. Even today the launch vehicles we use are dependable, but not totally flawless.

The plutonium contained within each RTG is in the form of the heat-resistant, ceramic form of plutonium dioxide. The argument here is that because the fuel is in ceramic form, this will prevent the plutonium from becoming vaporized dust. If the plutonium does in fact become vaporized dust, it can then be inhaled exposing the victim to large doses of cancer causing radiation. The claim is that the ceramic pieces will not be vaporized due to a launch vehicle explosion. They will instead break into chunks which can then be retrieved.

Under most situations this claim is true. But isn't there a situation under which the ceramic fuel could be vaporized? As a matter of fact, there is. NASA admits that fuel vaporization could occur if the space probe in question were to burn up in the atmosphere. This could occur if the launch vehicle falls back to Earth from high up in the atmosphere, or if it exploded high up in the atmosphere, or by the probe making an accidental re-entry during a near-Earth flyby.

However, Cassini is already on its way to Saturn, via Venus and a near-Earth flyby in 1999. So far, everything has gone well, and there is only a very small chance that it could burn up in the atmosphere due to an error during its near-Earth flyby in 1999.

But my concern is not just with the Cassini mission, but mostly with future missions in which RTG's are to be used. Space exploration is important, and for so many reasons. But, we need a dependable power source to supply the equipment we use to gather the data we want to collect. So far RTG's have been our only source for deep space exploration. Even if solar technology is improved drastically, there will still be a need for an alternate power source where solar technology simply cannot be used.

The question still lingers. Aside from the obvious scientific advantages, are RTG's really safe? Are we not asking the public to put itself at risk in the name of space exploration? If this were a spy satellite and not a probe designed to do scientific research, would we be so willing to take the risk?
 
 

The first Image of M42 above is a 600 second (10 min.) Exposure taken to bring out the very faint part of the Nebulae. The second is at 1200 second (20min.) exposure also of M42. I did these to see how well my telescope would track on long exposer. Both images where taken on the January 27, 1998 at 20:58:50 and 21:32:41 MST respectively. Both were f/6.3. I was using my ST-4 to guide. Both images are as they where taken in their raw state, that is they have not been processed. In the second image you can see how the nebulae is over exposed but still brings out a lot of detail in the faint part of the nebulae toward the right side. The field of view is 22.38 by 29.52 arc. minutes for both images. The ST-6 temperature was set at -40 Celsius.
 

"Exactly how do stars form from gas clouds"?

We see gas clouds in many different stages of size, temperature and density, but it seems that stars form when portions of these clouds become unstable to gravitational collapse. The details are very complex and there are many different physical 'triggers' that can cause parts of clouds to begin to collapse. The cloud, globule, or core, is often only a fraction of a light year across at the start, with a density of only a few thousand atoms Per cubic centimeter. After a million years of less, the density of the center of the cloud has increased many million-fold and the collapsing material forms a central 'proto-star' mass usually surrounded by a rotating disk of residual matter supported in the proto-stars equatorial plane by the centrifugal force of rotation. The proto-stellar core continues collapsing until it becomes opaque to its own radiation ( mostly infrared) and then slows down collapsing a bit...but by this time so much mass has assembled that the core temperature is over 1 million degrees and thermonuclear fusion begins to take place. The young star then rearranges itself internally with large convective regions near the surface to transport the

heat out to the surface. The whole process takes a few million years from start to finish!
 

"How are logarithms used to measure the brightness of a star"?

The Greek 'astronomer' Hypparchos cataloged the 1000 brightest stars into roughly 5 ranks or magnitudes. The brightest dozen or so were the stars of the First Magnitude, the next brightest were the stars of the Second Magnitude...and the faintest ones were of the Fifth Magnitude. Today, we still use this system which we call the visual magnitude system. As it turns out, these magnitude groupings correspond to changes in brightness of a factor of the fifth root of 100 or (100)^.2 . This is a logarithmic scale in powers of ten such that:

-.4(magnitude) Brightness = 10

which means that if you have two stars that differ by 5 magnitudes in apparent brightness, this corresponds to a factor of 100 in actual brightness difference. A 10-magnitude difference is a factor of 10,000 in brightness. The difference between the brightness of the sun ( magnitude -26) and the faintest stars that the Hubble Space Telescope can regularly study ( magnitude + 24) is a difference in magnitude of 50, so that the actual brightness range is a factor of 10^(0.2*50) or 10 billion.

(All answers are provided by Dr. Sten Odenwald (Hughes STX) for the NASA IMAGE/POETRY project.)