Download PDF version:
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. 6 $5.00 a year July 1983
Editor........Rolf Meier.....4-A Arnold Dr.......820-5784
Addresses.... Art Fraser......11-860 Cahill Dr....737-4110
Circulation...Robin Molson....2029 Garfield Ave...225-3082
OBSERVER'S GROUP MEETING - JUNE 3 David Lauzon
Ottawa Centre President Peter MacKinnon opened the meeting, which was held in the NRC auditorium, at 8:15 pm with about 45 people in attendance. Since this Centre meeting was being presented by the Observer's Group, Peter handed the proceedings over to Chairman Rolf Meier after making some opening remarks.
With this being instrument night, members were urged look at the many fine telescopes. This meeting gave members a chance to show and tell of their recent projects.
Rolf reminded members of the changes for the next two meetings. The July meeting will be held on June 24, and the August meeting will be held on July 29.
Robin Molson gave a short status report on the Indian River Observatory. He also mentioned that non-keyholders be sure to call around to be sure that the observatory is open.
Vice-Chairman Gary Susick presented the observational speakers of the night.
First up was Dave Fedosiewich, our comet coordinator, talking about Comet IRAS-Araki-Alcock which reached a brilliant magnitude 1.7 on May 12. The reported fan shape was due to the rotating nucleus discharging material in all directions. Another comet which has been recently discovered is Sugano-Saigusa-Fujikawa, which will be seen in the morning sky in June. Still another comet, IRAS, is too faint to be seen at magnitude 17. Dave's talk ended with an open discussion on film resolution.
Following Dave's talk was Linda Warren, showing slides of Comet IRAS-Araki-Alcock taken near Peterborough. Her slides showed the incredible speed of this comet.
Astrophotography coordinator Frank Roy presented a slide show on how different f-stops affect deep sky photographs. He says that f/2.8 gives him the best results for piggyback photography, but one should adapt each exposure to the prevailing sky conditions.
Sandy Thuesen and Brian Burke showed some outstanding slides of the General Assembly, and the city where it was held, Quebec City.
This meeting being instrument night, many projects were on display. Frank Roy explained the operation of the new digital readout for the 16-inch telescope at IRO. Gary Susick showed how his new Celestron Schmidt-Newtonian works. Max Stewart described his 6-inch f/8 Newtonian, which is made all of wood (except for the optics). Rolf Meier presented the group's new 10-inch f/4.6 Newtonian, with parts supplied by various members. Brian Stokoe had a Questar, Fred Lossing showed his 10-inch f/4 Newtonian, and Linda Warren demonstrated her Observer's Unit.
Rolf and Peter closed the meeting at 10:05 pm, and welcomed people to look at the displays.
* * *
TELESCOPE AND INSTRUMENTATION WORKSHOP Malcom Lambourne
location: 312 Woodroffe Avenue, Ottawa (see map in April Astronotes)
dates: Tuesday July 5 6:30 to 10:30
* * *
Did members catch a glimpse of the Space Shuttle Enterprise during its brief stay in Ottawa?
The flyby on Wednesday afternoon was tremendous, under perfect sky conditions. The biggest traffic jam in Ottawa history was reported as 300,000 people flocked to the airport to see the spacecraft atop the 747 carrier. A spectacular sight! -Ed.
COMET IRAS-ARAKI-ALCOCK Sandy Thuesen
Although cloudy skies in the Ottawa area prevented observations of this comet in the week of May 9, we were lucky enough to catch it briefly on the Wednesday and Thursday nights from IRO.
On May 11, along with Dave Fedosiewich and Jamie Black, we waited out cloud until about 22:30, when the sky began to clear in Ursa Major. We were not sure of the exact position of the comet for that night, so we started looking for it in that area. However, when the sky suddenly cleared in Cancer we were surprised to see a large, bright, hazy object right next to M 44. We were amazed at the size and brightness of the comet! The fan shape was evident in binoculars and it took up the entire field in the eyepiece of the 16-inch. Dave estimated its magnitude at 3.0. Cloud quickly moved in again and by 23:00 it could no longer be seen, but at one point later on it could just be detected through cloud, it was so bright.
On Thursday night, however, it was a lot harder to find the comet in the evening sky. We found it in binoculars very low in Hydra, just southeast of M 48. As a matter of fact we thought M 48 was the comet for a short while, as it was rather faint as well. With some difficulty it was found in the 16-inch and just before it became too low to observe I sketched its position on two occasions, twenty minutes apart. I regretted not thinking of the idea sooner, as its movement against the background stars could be seen even in that short period of time, and it would have been interesting to have a series of sketches over the two nights.
Having the opportunity to observe the comet on two nights was great!
JULY METEORS Dave Lauzon
The Southern Delta Aquarid meteor shower peaks this year on July 28 at 22:00 EDT. This shower is spread over a long period of time, and runs into the time of the Perseids. These meteors are relatively slow, with a speed of 41 km/sec. The moon is in the last quarter phase and the radiant rises around 21:00. Observing this shower would be good practise for the Perseids next month. A meteor session will be planned for this month. See you there!
Other shower activity: the Northern Delta Aquarids (July 14 - August 5) peak on August 12; the Alpha Capricornids (July 15 - August 10) peak on July 30; the Southern Iota Aquarids (July 15 - August 25) peak on August 5, and the Northern Iota Aquarids (July 15 - September 20) peak on August 20. More information will be given at the July meeting.
A -6 magnitude fireball was reported by Malcom Lambourne on the night of June 4/5 at about 11:30. While observing in Stittsville, Malcom and others spotted this yellowish white meteor break up into 5 or 6 fragments. It was first spotted in the southwest and slowly hurled west, parallel with the horizon, with a trail about 20° in length.
I also saw this meteor (at the Airport Drive-In?!) and noticed that it was bright green and about magnitude -3. Anyone else who has seen this and recorded it please give me a call at 745-7962.
* * *
DIGITAL DISPLAY FOR IRO UPDATED Frank Roy
Recently, the digital display of the Indian River Observatory was modified to increase the stability and reliability of the readout.
The display system, which I installed in October, 1981 with the help of Fred Lossing, reads out the position of the 16-inch telescope on an LED display.
Originally, the RA and Dec employed two different systems to measure the position of the telscope.
There are 6:1 and 3:1 reduction gears on the Dec and RA shafts respectively, coupled to precision 10-turn pots. The wiper voltage is then a function of the position of the axis. The RA value is converted to a 13-bit digital value which addresses a pair of ROM's which contain the actual hours and minutes of the RA position. The resolution is 1 minute of arc and the accuracy is 1 minute of RA.
Originally, the Dec used an Intersil voltmeter chip, which reads ±1.999 volts. Using only ±0.900 of the range, of course, meant that going over 90.0 degrees would give an erroneous result. Also, the decimal digit would read in decimal hours, or 6-minute increments.
It was also noticed that the Dec readout shifted by about 1 degree from night to night. The design made calibration difficult. Finally, the Dec could not be used throughout the full range of the scope because crossing the pole would give readings greater than 90 degrees.
Bothered by these drawbacks, in March I attempted to modify the original Dec circuit with little success. Frustrated, in April I decided to rebuild all the Dec circuitry starting from scratch, using a completely different system.
In May, I removed the system from IRO and began the job by clearing the main circuit board of existing Dec circuitry. The new system essentially employs the same circuit that the RA was already using. The 13-bit analog to digital converter used with the RA is multiplexed to read both RA and Dec. All that was needed was extra timing circuitry to measure and to latch the proper displays. Also, the density of the memories was increased by a factor of 2 to store the additional declination numbers.
The new system was installed on June 7 and has a range to -83° 40'. The Dec now reads in 10-minute increments and has improved accuracy and stability. Also, calibration has been greatly simplified.
* * *
ORGANIC MOLECULES IN SPACE (FINALE) David Lauzon
Over the past few months, I've been writing articles on organic molecules in space. This month I would like to touch on the chemistry of interstellar space.
The main theories of chemical evolution are photoionization, photodissociation, collisions, reactions on grain surfaces, and circumstellar shell formation followed by ejection in the interstellar medium.
Photoionization and photodissociation occur due to ultraviolet light, with wavelengths roughly between 1000 and 2000 Angstroms. This allows new chemical bonds to be formed until a stable molecule is formed. Carbon monoxide (CO) is one of these molecules. This molecule is the second most abundant molecule in space. The table on the next page shows photolifetimes of some molecules vs the amount of light (starlight) blocked.
Collisions between two atoms are relatively rare, and do not have the proper binding energy. Therefore a third body, such as a photon or electron is needed.
Grains of dust or other matter act as catalysts to form molecules. The grain forms with an atom and the grain-atom combination form with another element. The new compound separates from the grain and becomes part of the interstellar medium.
When molecules in circumstellar shells are ejected they flow into space. An example of this is the Ring Nebula or the Dumbell Nebula.
These are the basic reactions which take place in interstellar space. A question that I would like to see answered is what is the chemistry of planetary atmospheres, such as Jupiter or Saturn. Anyone wishing to answer this is welcomed to write it in Astronotes.
The bibliography for this article is the same as my first article on this subject (p.6, April 1983 of this magazine). The table for photolifetimes was taken from R.H. Gammon's article "Chemistry of Interstellar Space", published in 1978, page 22.
* * *
The July Observer's Group meeting will be held on June 24, and the August meeting will be held on July 29. The September meeting, will, as usual, be held on the first Friday in that month.
* * *
Articles for the August issue of Astronotes are due by July 15.