OAS Executive Committee 

President- Dave Dunn Ph. (801) 544-7705

Vice Pres- Lee Priest Ph. (801) 479-5803

Secretary- Bob Tillotson Ph. (801) 773-8106

Treasurer- Doug Say (801) 731-7324

The April Meeting

The regular monthly meeting of the Ogden Astronomical Society will be held at 7:30 p.m. next Thursday April 12, 2001 in the Ott Planetarium on the Weber State University campus.

OAS president Dave Dunn has organized another in the series of "Show and Tell" meetings. Members are encouraged to bring the recent projects and accomplishments in astronomy.

Upcoming star parties will be discussed.

Minutes

Ogden Astronomical Society

March 8, 2001

The March 2001 meeting of the Ogden Astronomical Society was called to order in the Ott Planetarium at 7:30 p.m. by president David Dunn.

The Bates Elementary School star party is scheduled for Thursday March 22.

The Messier Marathon this month is set for the weekend of March 23 and 24 at the Golden Spike Nation Monument. Dave has details.

A Swap Meet is scheduled for Saturday April 14 at the Harmon's Center in Roy. Other astronomy clubs in the area will likely participate. Also at the Harmon's Center, a public star party is scheduled for April 27^th.

Another public star party at East Canyon State Park was discussed. June 30, 2001 is the most likely date.

CORRECTION: The date of the static firing of a Thiokol solid shuttle booster was mis-stated in last month's newsletter. The scheduled date is May 24, 2001. For additional details contact Steve Richer.

The evening's program was introduced; "Women Hold Up Half the Sky" is the current Ott Planetarium show.

Following the program, the meeting adjourned into discussion groups. Mark Durrwacher brought obsolete commercial grade computer hard drive disks to give away to the members.

Bob Tillotson, Secretary

Star Party in Ireland,

Anyone Interested?

The following message was sent to the OAS by David Bell, Secretary of the Shannonside Astronomy Club in Birr, Ireland:

Hi

My name is David Bell and I am the secretary of Shannonside Astronomy Club, Ireland. I apologize in advance for intruding on your time, but I just want to bring to your attention our annual Whirlpool Star Party, which is held every year in Birr, Co Offaly, Ireland. Birr, as you may know is the home of the Great Telescope built by the 3rd Earl of Rosse in 1846, and it has now been fully restored. The present Earl, the 7th, is our patron and he permits us the use of the castle demesne for our observation sessions.

The WSP is now the premier event of its kind in the UK and Ireland and is attracting people from all over the world. I am bringing it to your notice in case you might know of anyone who is planning a holiday in Ireland, and who might like to arrange it to coincide with the event, which will take place this year on the 14th, 15th and 16th of September.

The speakers arranged so far include the following Halton Arp, who, I am sure, needs no introduction. Jack Newton, astrophotographer. Professor Mike Edmunds from Wales who impersonates Sir Isaac Newton as an old man reminiscing about his life's work.

Dr Andy Newsam, an expert on robotic telescopy. Frank Prendergast, expert on Newgrange, the great Boyne Valley stone age tomb, (Frank has some original insights to Newgrange to his credit) and also the astronomical alignment of the standing stones of Ireland.

Florence and Kenneth Wood, authors of Homers Secret Iliad, a very persuasive argument that the Iliad is almost exclusively based on astronomy. The work is based on the work of Edna Leigh, from the US, who spent her life researching it. Florence is her daughter.

All in all, its a great weekend, although the Irish weather being what it is, we cannot guarantee that you will get any observing done. Because of this we must place the emphasis on having what we call in Ireland the 'craic' (That's 'a good time' to you). Thank you for your time, and if you think you know anyone who might be interested, you might pass this email on. Get in touch and I will be delighted to give you any further information I can.

Best regards

David Bell

By Jeremy Mathews

The cool spring nights of April present an inviting atmosphere to view many of the deep-sky objects in the regions of Hercules and Lyra. Start by looking for the northern hemisphere's King of globular clusters - M13. This large bright object is almost directly 1/3 of the way south on a line joining Eta and Zeta Herculis. For light-polluted skies, individual stars are most easily resolved halfway between the cluster's core and it's outermost edge. However, if extremely dark skies are

available, and an 8/10" scope, look just to the north of M13 to find the small, dim galaxy NGC 6207. Both M13 and NGC 6207 should be visible in the same field of view using medium magnification. M92 has an extremely dense central core even for a globular cluster. Although small, this cluster is very bright and makes a fine spectacle even in small instruments. It is much more difficult to find as there are no bright stars in the region. Located at 17h 17m R.A. and +43d 08m Dec, it is only slightly north to the midpoint of a line joining Tau and Upsilon Herculis. Further north at 16h 47m R.A. and +47d 32m Dec is NGC 6229. A 10" scope will show a small hazy glow which brightens somewhat in the center, however larger instruments are needed even to resolve individual stars at the cluster's edge. Moving east into Lyra is one of the most recognizable nebulae in the sky. The distinct doughnut shape of M57 can be seen even at very low powers. This nebulae is however, very small and may be mistaken for an out-of-focus star. It is very bright, and will stay sharp even if viewed at extremely high magnifications. It is best found by scanning the central portion of a line joining the Beta and Lambda stars in Lyra.

Two double stars worth looking at are Delta Herculis and 100 Herculis. Located at 17h 15m R.A. and +24d 50m Dec, Delta Herculis is the brightest star in Hercules' eastern leg. It is a fine double whose 3rd magnitude primary is a brilliant white and whose 8th magnitude secondary shows a bluish-purple hue. The separation angle of 8.9" makes it easy to identify as a close double. East of Delta Herculis and south-east of Xi Herculis lies 100 Herculis. This double makes a good object for binoculars as it's primary and secondary shine at roughly 6th magnitude each. These two bright white stars are found at18h 07m R.A. and +26d 06m Dec.

My Experiences Putting Together A Radio Telescope, Part 2

By Dale Hooper

In last month's article, I mentioned some basics about radio astronomy, how to turn a used C Band satellite dish into a radio telescope, and the front-end electrical components (the components at or near the dish antenna) required. Figure 1 is a picture of my dish along with the front-end electronics.

 

Figure 1 - 10 foot mesh dish, feed horn assembly, and Low Noise Amplifier (LNA) (Click for larger image.)

In this month's article we'll cover the back-end electrical components as well as computer configuration and software. As I mentioned in last month's article, the signal is received by the dish antenna, focused into a feed horn, amplified by a low noise amplifier (LNA) and then transmitted along very low-loss coaxial cable.

The signal is then passed to a receiver. The frequency range I am interested in is in the microwave range of the radio spectrum (L Band). Some amateur radio astronomers use a down converter to shift the microwaves into a different frequency range such as the Ham band at 144 MHz. But, I chose to instead use a microwave receiver. Assuming you already own a microcomputer, the receiver is the most expensive part of the radio telescope system.

Receivers that are useful for the type of radio astronomy I am doing need to at least cover the range between 1400 ­ 1700 MHz. This area is sometimes known as the "water hole" because it covers the emission wavelength of neutral hydrogen (1420 MHz) and the emission wavelength for the hydroxyl radical (1638 MHz). When hydrogen is combined with a hydroxyl radical a water molecule is formed. This area is important because there is a lot of hydrogen and OH in the galaxy. The receiver I chose is an Icom IC-R7000 which is the type shown in Figure 2. This is a very stable receiver and there is a lot of software that has been written to use it. I was able to purchase one second-hand for about $800. There are other receivers which could be used that range in price from around $500 to $2500.


Figure 2 - Icom IC-R7000, 25 MHz - 2 GHz Receiver (Click for larger image.)

In Figure 1 from last month's article, a control cable is connected to the serial port of the computer to control the scanning frequency and mode of the receiver. An audio cable is also used to send the signal from the receiver to the microphone input of the computer sound card.

I'm using free radio astronomy data acquisition software that is available on the Internet. The software is called SETIFox and it was developed to support amateur SETI work. However, it is also very useful for general amateur radio astronomy. SETIFox allows the sound card to be used as an analog to digital (A/D) converter for acquiring the signal into the computer. Figure 3 is a screen shot of some of the current work that I am doing.

When the radio telescope is completely assembled, there are two important things that are available for testing and trouble shooting the system. The first is a calibrated noise source. I purchased one from Radio Astronomy Supplies, but they are also available from Down East Microwave (as a kit or assembled). I added a 5 cm quarter wave antenna so that it would work in the frequency range I needed. I would be willing to loan my calibrated noise source to other club members. The second important test tool is the Sun. The Sun is a pretty good blackbody, which basically means it is a good emitter at practically every frequency. Drift scans of the Sun are very helpful for determining if things are working right and also for determining proper alignment of the dish and feed horn.

Figure 3 - Drift Scan Near the celestial equator: The "nearly" sinusoidal wave above (in the Intensity Chart) gives a clear indication of the peak of the neutral hydrogen line. The Waveform Graph shows an individual scan from 1420.0 MHz to 1421.0 MHz. The bright line around scan # 135 is "interference" from the Sun, which during this scan was around 22:30 RA . The diffuse peaks around scans 58-68, 116-124, and 174-178 coincide with the plane of the galaxy. (Click for larger image.)

Building the radio telescope and doing actual radio astronomy has been and continues to be a lot of fun and a good challenge. There are a lot of exciting projects that I have planned. In addition, I can do radio astronomy on the cloudiest of days. In fact, the only things that have shut me down so far are power outages, high wind, and major snowstorms.

I am currently performing scans of most of the sky (at four degree slice at a time). The neutral hydrogen emission happens at a very specific frequency of 1420.40575 MHz. As a result, it's really easy to get a Doppler shift measurement from the received data. So, I am creating scans of the sky and then going back to the same part of the sky six months later ­ in order to subtract the Doppler shift caused by the earth going around the Sun. This will allow me to produce a rough residual Doppler map of the sky (in neutral hydrogen). Also, with this same data, I'll be able to produce a rough map of the (neutral hydrogen) radio sky.

If there is enough interest, I'll write another article for the Star Diagonal after I get the data analyzed. I'd also be happy to assist anyone that might be interested in building a radio telescope of their own.

As I mentioned in last month's article, it is only recently that an amateur could put together a radio telescope like this without being well versed in electronics. This has the potential to open up radio astronomy to a much wider audience. There are two major "windows" into the electromagnetic spectrum that aren't blocked by our atmosphere: the visible range and radio frequencies. There are many exciting discoveries that await amateur radio astronomers as we learn to look through the second window.

Items Discussed this time, Sources of information and products, and Notes

1. http://www.bambi.net/sara.html: This is the website for the Society of Amateur Radio Astronomers. This is an excellent source of information and further contacts. They also produce a bi-monthly journal.

2. Bernard F. Burke and Francis Graham-Smith, 1997. An Introduction To Radio Astronomy. Cambridge University Press, Cambridge, UK. Covers the basics of radio telescopes and radio astronomy in a semi-technical format.

3. Microwave receivers, the Icom R7000, R7100 (both discontinued), and R8500 receivers, http://www.icomamerica.com, work really well. The AOR AR5000, http://www.aorusa.com, is another excellent choice and there are others.

4. Computers: The level of number crunching required probably means that a higher end Pentium II or Celeron is necessary. I use a 450 MHz Pentium III. However, since the sound card is being used as an A/D, it can't be used for anything else while data is being acquired, but its fun to listen to the "hiss" of neutral hydrogen.

5. http://php.ucs.indiana.edu/~foxd/home-seti.html: This is the home page for the SETIFox software written by Daniel Fox, KF9ET.

Jim Seargeant's - Images

Big Spot! (Click for larger image.)

Patrick Wiggins and others had been sending alerts of large sunspots visible on, so Saturday morning I set up my 8" with its solar filter and there they were! There were quite a few high clouds, but this was too good a chance to pass up. I unlimbered by LX200, put on the solar filter, started taking pictures, and this is the result.

The hardware used was a 12" LX200 operating at f/6.3, and the SBIG CFW8 color wheel and ST7 CCD camera. The solar filter is a piece of Baader material covering a 3 1/4 in mask. This gives ample illumination for the ST7; in fact without the color filters even the shortest exposure time possible, .11 sec, causes an overexposure. Twenty exposures each of red, green, and blue were taken. Because of the clouds drifting by, only about 10 shots out of each 20 were sharp enough to keep. Each image was calibrated using a dark frame and then each color set was registered and combined using Mira A/P. Each combined color image was enhanced with an unsharp mask, then all three were combined into a single color image using the AIP4WIN software. I'm still learing how to get the color balance right so this image is a bit too red, although that may be a normal result because of limb darkening toward the edge of the sun. The processing to get this result took about 6 hours.

The following article on this particular sunspot appeared on www.nasa.gov.

 - - - - - - - - -
Dolores Beasley

Headquarters, Washington,

DC March 30, 2001

(Phone: 202/358-1753)

Bill Steigerwald

Goddard Space Flight Center,

Greenbelt, MD (Phone: 301/286-5017)

RELEASE: 01-59

NOW PLAYING AT THE STAR NEAREST YOU: THE LARGEST SUNSPOT IN TEN YEARS BLAZES AWAY WITH ERUPTIONS

A huge sunspot, thirteen-times larger than the surface area of the Earth and growing, has now rotated with the Sun to face our planet. The sunspot, which is the largest of the current solar cycle, is also the largest to appear in a decade.

The area of the Sun, designated AR 9393, has been a prolific generator of stormy solar activity, hurling clouds of electrified gas towards Earth, producing four explosions, called flares, and spawning storms of high-speed particles in space.

The largest of the four flares occurred at 4:57 a.m. EST on Thursday, March 29, and was rated as an X-class flare, the most potent designation. The other three flares were rated M- class, second only to the X-class. An eruption near AR 9393 hurled a cloud of electrified, magnetic gas towards Earth on Wednesday. This eruption, called a Coronal Mass Ejection may cause auroral displays and magnetic storm activity when it impacts the Earth's magnetic field sometime Friday. Another Earthbound CME associated with the X-class flare was seen at 5:26 a.m. EST March 29 and is expected to arrive on Saturday.

"Sunspots with complex magnetic field structures like those in AR 9393 can generate big flares, and sure enough, we just had a powerful X-class flare from this area," said Dr. Joseph Gurman, at NASA's Goddard Space Flight Center, Greenbelt, MD, project scientist for the Solar and Heliospheric Observatory (SOHO) spacecraft. SOHO is one of a fleet of sun-observing spacecraft now tracking this region and its activity.

Sunspots are darker areas on the visible surface of the Sun caused by a concentration of distorted magnetic fields. The strong magnetic field slows the flow of heat from the Sun's interior and keeps sunspots slightly cooler than their surroundings, causing them to appear dark. The number of sunspots increases and decreases as the Sun's 11-year cycle of stormy activity rises and falls. Violent solar activity is believed to be caused by the release of magnetic energy, and powerful solar eruptions and flares often occur near the enhanced magnetic field of sunspots.

Solar flares, among the solar system's mightiest eruptions, are tremendous explosions in the Sun's atmosphere, capable of releasing as much energy as a billion megatons of TNT. Caused by the sudden release of magnetic energy, in just a few seconds flares can accelerate solar particles to very high velocities and heat solar material to tens of millions of degrees. Coronal mass ejections are clouds of electrified magnetic gas weighing billions of tons, hurled into space at speeds of 12 to 1,250 miles per second. Depending on the orientation of the magnetic fields carried by the ejection cloud, solar explosions cause magnetic storms by interacting with Earth's magnetic field, distorting its shape and accelerating electrically charged particles trapped within. Severe solar weather is often heralded by dramatic auroral displays, but magnetic storms are occasionally harmful, potentially affecting satellites, radio communications and power systems.

Coronal Mass Ejections and flares can produce storms of high- velocity particles. The ejections are believed to produce longer particle storms than flares, storms that sometimes last for days, as they plow through the slower solar wind at supersonic speeds, creating a shock wave that accelerates electrically charged particles.

The SOHO project is an international cooperative program between NASA and the European Space Agency in the framework of the international Solar Terrestrial Science Program.

Movies and images of this solar activity will be broadcast today on NASA Television, which is broadcast on satellite GE- 2, transponder 9C, C-band, located at 85 degrees West longitude. The frequency is 3880 MHz, with vertical polarization and monaural audio at 6.8 MHz"

For more information on the sunspot, refer to: http://www.spaceweather.com/

Jim Seargeant