AstroNotes 1983 September Vol: 22 issue 08

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A S T R O N O T E S  ISSN 0048-8682

The Newsletter Magazine of the Ottawa Centre of the RASC
Vol. 22, No. 8 $5.00 a year September 1983

Editor.......Rolf Meier......4-A Arnold Dr___...820-5784
Addresses....Art Fraser..........................737-4110
Circulation...Robin Molson....2029 Garfield Ave...225-3082

 

STAR NIGHTS

On August 12, a public star night was held at the Indian River Observatory. The region which was invited, of course, was the community of Almonte. Although they were scared off at the beginning of the night because of some lingering haze, those that did show up after 10:30 or so were treated to some fine sights as it cleared nicely.

There was also a meteor session for the purpose of observing
the Perseids after midnight, and 6 observers saw several hundred meteors. A fine night.

Thanks go to Brian Burke, who, in my absence, advised the media of this star night.

The next regional public star night will be held in the community of Barrhaven on the evening of Friday, September 9. While the skies are dark there, since it is far south of the city of Ottawa, nearly every street has bright lights, and at the time of this writing I was still trying to locate a site that was shielded from the local lights. The announcement of the site will be made at the September Observer's Group meeting, and notice will be placed in the Nepean newspaper, the Clarion.

That will conclude this summer's regional star nights. In October, the Centre will be having its annual Deep Sky Weekend at IRO. Not only that, but the picnic will be held at the same site at the same time! Dates - October 8 for the picnic and all weekend for deep sky observing.
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OBSERVER'S GROUP MEETING - JULY 29

Dave Lauzon

Chairman Rolf Meier opened the meeting at 8:20 pm with 27 people in attendance, of which 24 were members. Rolf gave notice that the next meeting will be held on September 2, in room 3001 as usual.

Observatory committee chairman Robin Molson reported that the guidescope for the 16-inch has been modified. The guidescope is now on top of the telescope when in the storage position.

Next up was OG vice-chairman Gary Susick with a talk on solar filters. The sun's rays must be cut down in intensity before heat builds up in the telescope, and this is done in one of two ways. The first is with aluminized mylar and the second is with metallized glass. The latter is ground and polished optically. UV and IR radiation is blocked and a small fraction of the visible light is passed. Gary then showed some some slides of many beautiful rainbows.

After Gary came meteor coordinator David Lauzon with a talk on the summer meteors in 1983. This year, the Perseids are expected to be very strong, and Dave urged that people observe this shower.

Variable star coordinator Brian Burke discussed the many grazes that will occur over the next few months. Brian told how grazes can be used to show the profile of the lunar limb. On August 3 there will be a graze at 3:12 am. On September 3, at 3:10 am, there will be another. On November 20, a grazing occultation will pass through IRO.

Eclipse adventurer Patrick Brewer fascinated members with a lengthy slide show of the recent total solar eclipse which occurred in Indonesia.

Last up was Rolf Meier with a slide show of the Quiet Site, the Space Shuttle, and the Holleford Meteor Crater, located just north of Kingston. Rolf also described a new Wright telescope built by himself and Linda Warren.

Rolf closed the meeting at 10:25 when people were invited for refreshments.

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STELLAFANE - 1983 Linda Warren

It seemed to take forever..."We're nearly there", only to find at every turn it was "just a little bit further".

Then through the trees I saw cars, tents, and just about everything else. "Wow, look at all the people." This being my first Stellafane really impressed me. It's somehow different from a General Assembly. It was extremely exciting to be around people, most of whom shared your interest in astronomy.

The first night we attended the evening talks. George Keene showed slides of the Java eclipse and Dennis di Cicco gave a very interesting slide show about his home-built observatory. We saw an entertaining show of "How not to Build a Telescope". We didn't stay for all the talks as they went on quite late.

The next day was the big one for me, with the telescope makers’ contest. We set up our telescope, a 6-inch f/3 Wright close to Steve Dodson's 22-inch f/7. Many people came by to take pictures and comment on the "Wright" telescope but unfortunately it must have been "wrong" because it didn't win an award. However, Steve Dodson won award for his drive mechanism, and Max Stewart won an award for his beautiful wooden 6-inch Dobsonian.

That night, Walter Scott Houston gave his "usual" talk and mentioned with regret that his good friend Fred "Lessing" was not able to attend. Roger Tuthill gave an emotional speech about Stellafane and commenced a "Save the Stellafane" fund with his contribution of $100. The main talk of the evening was by Dr. Paul Horowitz and was excellent and interesting. It was about radio telescopes and the Search for Extra-Terrestrial Intelligence (SETI). He showed slides of all the different radio telescopes, the most fascinating of course being the big one in Aracibo.

The whole weekend was well, to sum up, fun. I was sorry it was over so quickly, but already I'm looking forward to next year, the 50th Stellafane.

The best part of Stellafane for me was meeting new people, renewing past acquaintances, and sharing the "blazing exitement of Stellafane" with all of them.
 
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THE TAG PROJECT Brian Burke

Recently I was looking through the predictions for lunar grazing occultations for the second half of 1983, and besides the grazes of August 3 and September 3, there was another graze that looked very favourable. The listing showed that a 6.8-magnitude star would graze the dark south lunar limb on the morning of November 28, and the nearest point was only 25 km south of Ottawa. However, as I looked over the list of longitude and latitude, the numbers began to look familiar. I thought, "could it be possible that...". I then pulled out another sheet of paper that had the coordinates for IRO and my suspicions were confirmed. This graze should also be visible from the Indian River Observatory, as the limit line passes about 1.2 km south of the observatory.

This is the first time that the limit line for a graze will pass so close to IRO that events could be observed with the telescope. Such a rare occurrence cannot be allowed to pass by without a project. The project that I have in mind is based on recent success in the US in recording grazes on tape using video recording equipment. The recent success involved using a telescope as small as 20 cm with a video camera attached to it. Therefore, with a 40-cm telescope located within range of a grazing occultation, the Tape-A-Graze (TAG) project comes into existence.

The videotape of a graze made in the US revealed that the recorded events were gradual when the tape was played back at one tenth the speed. The gradual change in the star's light as it disappeared and reappeared behind limb features was caused by the Fresnel diffraction pattern. Although more detailed information from the Fresnel diffraction pattern can be obtained by using a photoelectric photometer, it would be very intriguing to observe this phenomenon visually. However, since the time signal can be recorded on the audio part of the videotape, some information can still be obtained from the Fresnel diffraction pattern.

If the TAG project is to be successful, however, I need the assistance of other members. Basically, a video recorder and light-weight video camera are needed. Over the next few months I would like to prepare for the November graze by observing some total lunar occultations using video equipment. We must also determine the best technique for attaching a video camera to the telescope. If you would like to get involved in this project, let me know at the next meeting or give me a call at 521-8856.

 
THE AUGUST GRAZE Brian Burke

A group of six of us met at the St. Laurent Shopping Centre on August 3 at 12:30 am for a graze expedition to a site 100 km south-east of Ottawa. The sky was clear and the temperature was pleasant. Everything looked great but Murphy got into the act early when another member failed to show due to confusion in the date of the graze. Three of the four cars arrived at the rendezvous point with time to spare. The fourth car eventually arrived after taking a little detour (?).

Three stations were established on a road where the graze line crossed. Sandy Thuesen and I were at the first station; 800 metres to the south, Louis Krushnisky and Frank Roy were at the second station, and at the third station located another 700 metres south, were John Amyot and Brian Stokoe. The distances shown on the diagram are for the perpendicular distances from the limit line, since the road was not quite perpendicular to the graze.

The 6.3-magnitude star was very easy to see and the events were also easy to observe. Multiple events were observed at all stations as can be seen from the diagram. However, a few other problems occurred. Again, the time signal could not be received on the one radio the group had for this expedition. Therefore it was necessary to call out the time from watches that had been set to CHU earlier in the day. The other problem occurred with my tape recorder. It developed a loud hiss and as a result the times for my last two reappearances were lost. Neither my voice nor Sandy's can be heard on parts of the tape. This is the reason that our station's two disappearances are recorded without a reappearance between them. The final reappearance was also not recorded.

Although this was a very successful graze, one important factor was missing. That factor was more stations. In order for these grazing occultation expeditions to be more successful we need more people involved so that more stations can be established. It is very difficult to obtain a lunar limb profile from just three stations. We also need more equipment. Radios that can receive the time signal, tape recorders, and portable telescopes are always in demand. If you could lend any of this equipment for grazes, please let me know. I hope to see more of you on the next graze expedition, which occurs on September 3.

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ASTEROIDAL OCCULTATIONS Brian Burke

There are two asteroidal occultations within the next nine days that should be observable from the Ottawa area. Some data for these two occultations are:

Occultation 1: Asteroid (53) Kalypso
Date and Time: September 9 at 00:06:30 EDT
Duration: 10 seconds
Star's Magnitude: 9.5
Star's Positon: 23h 46.2m -5° 42'
Asteroid's Magnitude: 12.3

Occultation 2: Asteroid (51) Nemausa
Date and Time: September 11 at 03:44:30 EDT
Duration: 13 seconds
Star's Magnitude: 5.9
Star's Position: 23h 31.6m -1° 31'
Asteroid's Magnitude: 10.6

The centre line for the first occultation passes about 0.1" northwest of Ottawa and since the angular diameter of Kalypso is 0.09", a slight southeast shift would at least produce a partial occultation.

The second occultation is rare because the star is visible to the naked eye. Although the centre line is 0.5" south of Ottawa, observers located within 1.4" of the predicted path should observe the star (14 Piscium) for possible secondary occultations. Observations should begin six minutes before and lasting until six minutes after the predicted time given.

Both stars will be more than 30° above the horizon at the time of the occultation. It is a good idea to locate the star using the finder charts a few days before the occultations and become familiar with the star field. You should record your observations using a tape recorder to record your voice and the time signal. I will be observing these two occultations from IRO but I encourage everyone to observe the occultations from their home or any other location.
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TOTAL SOLAR ECLIPSE - JUNE 11, 1983 Patrick Brewer

Along with a group of about 70 Canadian, American, and Dutch amateurs, I observed the eclipse from Salatiga in central Java. We were all travelling with the same tour company and were the only observers in the area. Salatiga is in a mountainous area and were able to escape the coastal heat and humidity. Although there were cumulus clouds on eclipse day, these dispersed as totality approached.

The eclipse itself was spectacular. We enjoyed 4:55 of totality. Most notable were the streamers. There were few prominences. Mars, Mercury, Venus, and Sirius were all easily seen. Shadow bands were observed before totality. There were bands spaced about four inches apart travelling away from the direction of the sun. There were also two other sets of bands with about one inch spacing shimmering at an angle of about 30 degrees either side of the main bands. We also noted that the sky was not as dark as expected for such a long eclipse.

The people of Salatiga went to great lengths to make our expedition a success. They had been planning for our arrival for six months. We were treated to two banquets and a show of local music, dancing, and costumes. In addition, ten English-speaking students from the local university acted as guides and interpreters for our group. The official eclipse observing site was excellent. Areas had been laid out for each observer and the view was unobstructed in all directions.

In every respect this was a super eclipse.
* * *

THE PLANETS IN SEPTEMBER Rolf Meier

It may seem that the planets have faded from view, now that brilliant Venus is no longer visible in the evening sky, and Jupiter and Saturn set soon after the sky becomes dark. But an amazing thing has happened! The planets are moving into the morning sky, and that is where you should look for them in September.

As mentioned, Venus has left the evening sky, but is now a thin crescent in the morning sky. Watch for greatest brilliancy at the end of the month. Around the middle of the month, Venus makes its closest approach to Mars.

Mars. Does the name still conjure up visions of a vast desert inhabited by ghost-like creatures? The mystery of the planet still remains, and the changing features as spring approaches still beg for an explanation. Now in the morning sky, Mars will appear gradually bigger until its opposition in 1984. Who knows what the careful observer will see.

Mercury reaches a favourable elongation in the morning at the end of the month. This is as good a time as any to see it.

These three planets will be dancing about near the constellation of Leo, and make some close approaches to Regulus. The moon also puts in an appearance at the end of the month.

So, try to be up early at least one morning this month, preferably toward the last half of the month, and watch the show!

 

COMING EVENTS
Wednesday, September 7    new moon
Friday, September 9    public star night in Barrhaven
Friday, September 9    occultation by Kalypso
Sunday, September 11    occultation by Nemausa
Thursday, September 22    full moon
Friday, September 23    due date for Astronotes
articles; the equinox
Thursday, October 6    mew moon
Friday, October 7    Observer's Group Meeting
October 7-9    Deep Sky Weekend, IRO
Saturday, October 8    RASC Ottawa Centre picnic at IRO
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