Category Archives: 1990

PeGASus Newsletter Issue #18 – Nov. 22, 1990

Hello, everyone!! As you can see, I am resuming the newsletter that I sent out to you before I went to Calgary last year. It seems to be a good way to keep us all in touch – I’d appreciate any comments (positive or negative) that you might have. [Contributions too, would be very welcome. What about it Chris, Jody, Dave, …?]


We had a good meeting in October (25th) with no fewer than 13 of us present and some others unable to attend. I was impressed with the new younger members and the degree of enthusiasm shown by all. It appears that the Prince George Astronomical Society is alive and well after a year in hibernation.

We had the necessary annual general meeting (sounds impressive, eh?) with agreement (elections?) as to who should be on the executive. Without wanting to sound too formal (we’re not!!), here it is:

  • President: Bob Nelson
  • Vice Pres: Al Pretty
  • Secretary: Brian Potts
  • Treasurer: Dave Sundberg
  • Memb at Large: Jody Silver

Exec. meetings will be held to a minimum, but we need some structure.

Many other things were discussed, including:

  • Badges and/or crests were proposed and will be looked into
  • A phoning “tree” has been set up and is enclosed
  • Fees were set at $20 for those working, $10 for students
  • Sky telescopes (Vanc’r) will give 25% off for PGAS members
  • We’re applying for a casino licence and date
  • We’re looking into a security system but need power
  • Signs for the door and road were proposed


Well, five of us went up there on the Saturday after the meeting. We fixed the door so that it closes easily (one person can do the job) and cleaned up generally. Other needed work (fixing the outhouse, fixing the porch railings, repainting the building, restoring the telescope, etc will have to wait for spring.) Generally, the observatory will remain dormant for the winter, although someone will have to call by periodically to check the place, reset the mousetraps, etc.


Mars is the big feature this fall. Its opposition time (the point at which it is directly opposite the sun in the sky and therefore closest to earth) will be November 27th at 2100 hours UT (1:00 PM PST). The following is taken from the Observer’s Handbook for 1990.

“Mars is the planet that has long captivated the imagination of mankind as a possible abode of life. Although the biology experiments in the two Viking spacecraft that landed on the planet in 1976 detected no known life processes in the Martian soil samples, there are many facets of Mars that make it the most Earthlike planet in the solar system. Volcanoes, polar caps at least partially composed of water ice, and ancient channels where water once flowed are amongst the most intriguing features. Observations from Earth as well as Mars-orbiting spacecraft have disclosed winds in the Martian atmosphere that reach speeds exceeding 300 km/h and raise vast amounts of dust that can envelop the planet for weeks at a time. The dust storms were though to occur with seasonal regularity shortly after Mars passed the perihelion point of its elliptical orbit, but the Viking observations revealed more complex weather patterns.

“In many ways Mars is the most interesting planet to observe with the unaided eye. It moves rapidly among the stars – its motion can usually be detected after an interval of less than a week – and it varies in brightness over a far greater range than any other planet. Mars may be distinguished by its orange-red colour, a hue that originates with the rust-coloured dust that covers much of the planet.

“Telescopically Mars is usually is a disappointingly small featureless ochre disk except within a few months of opposition when its distance from Earth is then near minimum. If Mars is at perihelion at these times, the separation can be as little as 56 million km. Such close approaches occur at intervals of 15 to 17 years; the most recent was in 1988. At a perihelion opposition the telescopic disk of Mars is 25 seconds of arc in diameter and much detail on the planet can be distinguished with telescopes of 100 mm aperture or greater. At oppositions other than when Mars is at perihelion, the disk will be correspondingly smaller.

“Late this year Mars will pass through its final favourable opposition in the 20th century for observers in mid-northern latitudes. The planet will reach 18″ in apparent diameter compared tp 24” two years ago during the excellent opposition of September 1988. However, Mars will be 25o higher in the sky when on the meridian which should partially compensate because telescopic images are generally steadier toward the zenith, all other factors being equal.

“… Overall, this is a favourable opposition for mid-northern latitudes – inferior to 1988, but better than any other close approach since 1973 and by far the best until 2003. …

“Any good-quality telescope over 70 mm aperture should reveal surface feature on the planet near opposition, including changes in the Martian dark zones from one opposition to the next. These alterations are due to he shifting climate regimes on Mars that regionally transport vast quantities of dust, both dark and light. …”

Hopefully, many of us will get out and look at Mars soon. I had a good time viewing Mars in 1988 and have many drawings, some reproduced in the Newsletter to show for it. I always saw the south polar ice cap and usually dark features that could be correlated with observations at other times.

Other planets: Mercury is east of the sun but hard to see. Venus is on the other side of the sun, just past superior conjunction. Jupiter rises before midnight and is high in the sky by sunrise. It will be a good object to view after the new year (unless you wish to stay up to the wee hours.) Saturn is low in the southern sky at sunset and sets 4 hours later.

Other objects: Orion (and with it, the magnificent Orion nebula) is up in the late evening sky and is well placed for viewing. The Milky Way in Auriga contains many open clusters that should keep observers happy finding them. The Crab Nebula (M1) is nearby and a challenging object. Let’s get out whenever it clears next and go after these objects!


Wednesday, Nov 28 at 7:30 in the Physics Lab (Rm 2-223) at the College. If you have a telescope, why not bring it in and we can have a go at cleaning the optics, collimating and adjusting it plus possible making or repairing parts as necessary. This is your opportunity to get your scope in top condition! If you do not have a telescope, that doesn’t matter as you’ll be welcome to watch, kibbitz, help, (heckle?), or just generally learn and gain experience.

Also: Brian Potts suggested that we should get going on mounting my 10″ mirror, to make a club telescope that all members can borrow and use. The construction can be quite simple and it will give us something to work on in the snowy cold weather when we can’t observe! The main problem is finding a good place to work (preferably on Saturdays); I’m making inquiries – if any of you have ideas, please let me know.

See you at the meeting!

Bob Nelson, President

PeGASus Newsletter Issue #17 – Jan. 20, 1990

Happy New Year, everyone! Hey, did you realize that this is the 10th year of existence of the Prince George Astronomical Society? Although our date of incorporation was 1980 April 18th, we were active before that, as our initial grant of $12,600 from the B.C. Lotteries was received in 1979 August. Needless to say, we’ve come a long way! One of these times I’ll give a slide show depicting the history of the observatory project.


There is very little to report about the building. I was up there a couple of weeks ago and there have been no more break-ins or more mice in the building. However, a little snow does get in under the door, though.

Fundraising is proceeding as planned. Six PGAS volunteers helped out (8 hours at a time!) at the North Nechako Lions’ casino nights in December; their names are: Rod Marynovich, Gail Brawn, Peter Bowen, Bob Ingraham, John Crow and Bob Nelson. Many, many thanks to these people — this will mean a donation of more money than we have seen for a while (around $600) and a good start on our fundraising. ($1000 has been promised from Northwood Pulp and Timber, to be paid when we get going.)

I recently submitted the application for a repeat grant from the B.C. Lotteries. Although I have no indication of what our chances are, we gave it our best shot and it looks good — included were some nice letters of recommendation from our local representatives, the mayor and others.

Next in line are applications to other Prince George industries for further donations. The money should ben there if we get out and hustle.

By the way, our own casino night is scheduled for 1989 July 30, 31, Aug 1. There should be nothing holding us back (so I’ve been told) from earning $5000 – 6000. If all of you could keep these dates in mind, it would be appreciated.


I went out early in January (Jan 6/7) to the Forests for the World, passing the message on the phone “tree”. The only people that joined me were a couple of youths in a car that happened by — they were quite happy to see Jupiter, the Orion Nebula, etc. It was quite cold, though (-25 deg C) — I had to quit after a couple of hours for fear of frostbite. It’s not always this bad — really!

We are planning to continue with the school observing; Al Pretty has several groups lined up. Those who own telescopes have been asked to keep these dates in mind; we should be able to field 1 or 2 telescopes per event. Those who have experience but no telescope are reminded that we have a telescope or two that could be loaned for the night.


Well, Jupiter is still prominent. Have you seen it yet?

Other than that, the sky is slipping around as usual. Overhead at 10 PM is Auriga with the rich constellations of Orion, Gemini, and Canis Major nearby. But looming in the eastern sky are Cancer (Beehive Cluster) and Leo with all its distant galaxies. Why not come out next time and see a few?

FEATURE ARTICLE – The Moons of Jupiter, by Bob Nelson

At last count (Observer’s Handbook 1989) there were 16 moons of Jupiter. But most of these are very faint — it doesn’t matter what kind of telescope you have (from 2″ to 36″ or so), you’ll see 4 moons: Io, Europa, Ganymede, and Calisto (ranging in brightness from magnitude 4.6 to 5.6). (Amalthea at magnitude 14.1 is the brightest of the rest.) The Voyager spacecraft have revealed these to be icy worlds similar in size to our own moon. But how were these discovered?

The first to see the moons of Jupiter was Galileo (1564-1642). This was a man that was very much a Renaissance scientist, laying the groundwork in physics for the great Isaac Newton. Galileo was also the first to gaze at the heavens with a telescope, which had just been invented (in 1610). (What a treat, to be the first!!)

Galileo discovered:

  1. The mountains on the Moon. These proved that the Moon was a body like the Earth. Galileo was also able to estimate the height of some of the mountains.
  2. Sunspots. These were controversial at the time as many thought that the Sun, a heavenly body, ought to be ‘perfect’.
  3. The phases of Venus (similar to those of the Moon). Because the gibbous phase was one of the phases of Venus that Galileo saw, this proved that Venus orbited the Sun and not the Earth, as in the Ptolemaic (Earth-centred) model of the solar system.
  4. The rings of Saturn. Galileo did not see these as rings since, at the time, they were almost edge-on. Galileo still gets the credit for the discovery, though.
  5. The four brightest (Galilean) moons of Jupiter. Galileo was fascinated by these, observing them night by night. (A copy of his sketches is given.) The importance of this discovery was that here was a solar system in miniature, lending credence to Kepler’s model.

I am fortunate enough to own a program for my (Apple) computer called ‘The Observatory’. This is like other observatory programs (there are so many around) which display the sky from any location and for any date and time. But this one is characterized by a high precision, and also the ability to ‘zoom in’ by magnifications of up to 512 x.

I’ve been able to duplicate the first 10 (so far) of Galileo’s sketches. They were all made early in the morning (about 4 AM, local time) as Jupiter was low in the northeast. The height was only 7-10 degrees above the horizon in most cases — this would mean that Galileo was looking through between 5 and 7.5 atmospheres and obviously had to struggle with a poor and fuzzy image. (No light pollution, though!!!)

Perhaps it’s remarkable that the correspondence is so close — The Observatory’s spacings (in units of Jupiter’s equatorial diameter) agree well with Galileo’s data. Once in a while, Galileo appears to have missed a moon close to Jupiter or to another moon, but this is understandable in view of the viewing conditions and his primitive telescope. (If you want to see the program in action, come to the next meeting.)

By the way, it is very helpful to specialists in celestial mechanics to have observations that go back so far — very precise values for the orbital periods result. Another note — Galileo is reputed to have observed Neptune (on the night of 1613 Jan 28/29) since he included this ‘star’ in his sketches of Jupiter, its moons and the star SAO 119234. The position of Jupiter is in disagreement with our knowledge of the outer solar system, but that may be somewhat understandable since Neptune has not made a full orbit since its discovery in 1846. (But, is there a 10th planet out there perturbing Neptune???)

The other significance of the moons of Jupiter is that, by careful timings, the Danish astronomer Roemer was able (in 1675) to estimate the speed of light. (When Jupiter was near conjunction — on the other side of the sun — the re-appearance of the moon Io was late by around 16 minutes, behind times when Jupiter was near opposition. Roemer attributed this tardiness to the time it takes light to travel the extra distance — the diameter of the Earth’s orbit.) Unfortunately, the graphics are not precise enough to duplicate this phenomenon.

Apart from orbital data, the vast bulk of our knowledge of Jupiter and its moons comes from spacecraft such as Voyagers 1 and 2. However, there is still a need for Earth-bound observations.


Wednesday, January 25 at 7:30 at CNC in room 2-223 (the Physics Lab). In response to positive responses, I’ll be showing my slides of Kitt Peak and Mount Hopkins Observatories that I took during my trip to Tucson, Arizona in July, 1980. What a way to escape the winter for an hour or so!

Bob Nelson, President