Canopus
May 1997

The Monthly Journal
of the Johannesburg Centre of the
Astronomical Society of Southern Africa

Box 93145 Yeoville 2143 - 18a Gill Street Observatory

Eben van Zyl

… demonstrates how an amateur astronomer can, with some very simple equipment …

Weigh the Sun

Danie Overbeek keeps us up to date with astronomical events in Danie's Corner. After the meeting we uncap our telescopes and invite everyone to spend some time viewing the night sky. Tea, coffee and biscuits are served after the meeting.

6 JUNE -- We entertain staff from the Schonland Nuclear Research Facility. You may recall that Schonland opened their doors for centre members to visit their facility. As a reciprocal gesture we invited them to join us for a braai and star viewing evening. Let's make this a memorable occasion for them.

5 JULY – Weekend Star-party in Swinbourne organised by Ed Finlay. Bookings are open for this special event. Although there is limited space available at Swinbourne, there is further accommodation available in Harrismith and Van Reenen's Pass. Please contact Ed

POSSIBLE FUTURE – Visit to SAAO (South African Astronomical Observatory) at Sutherland to be organised by Trevor Gould.

Hale-Bopp caused a great deal of excitement around, with all sorts of things happening around it,

Dr Block taking people to Namibia and looking for it in the desert, Tom Budge climbing rotting forest station towers in the Northern Transvaal for an M-Net program, Toms’ Radio shows and so on. Wherever you go, people are talking about it. Nice to see people enthused about something astro-wise.

Saturday night was deep sky night, and although the clouds were everywhere on Saturday afternoon, I packed the car, and drove out to Protea Ranch. At about 19:00, the skies cleared, and I spent a really nice three-and-a-half hours looking at the stars. All sorts of wonderful objects that I do not know the names of, clusters, nebulae galaxies and so on. I will learn them in time. I tried out my new 15mm Plossl eyepiece and a tele-compressor that I borrowed from a friend. Really nice views with these. The tele-compressor is really nice, a friend is going to make me one that fits in the baffle tube of the C8, I look forward to that.

Thank you Tom for the loan of the facilities.

In other departments, I have started building my cookbook camera, I have all the components except the CCD and the analogue to digital converter, which are on order. The wonderful way in which the instructions are presented enables you to build almost all the electronics without these chips.

I have decided to build an air-cooled version of the camera as lugging water containers and pumps around the countryside does not really appeal to me. Redesigning the camera head, and using two stage semi-conductor heat pumps will enable the camera head to be cooled enough for decent photography. If anyone has done this, please email me with your thoughts.

I have also started building a telescope driver that I found on the internet. Alt and Azimuth stepper motor driver circuits, with control provided through the parallel port of the computer. The software is clever enough to cater for periodic errors, gear backlash, scope alignment and so on. The project was designed by Mel Bartels, and placed into the public domain. The internet address escapes me at the moment, but search for ‘Bartels’. His page is entitled "Motorise your Dobsonian".

That’s it for this month.

Various minor problems (sunburn, possibly "the bends", certainly some [mild, reversible, painless] swelling of skin and underlying tissue) start after ten seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate. After perhaps one or two minutes, you’re dying. The limits are not really known.

You do not explode and your blood does not boil because of the containing effect of your skin and circulatory system. You do not instantly freeze because, although the space environment is typically very cold, heat does not transfer away from a body quickly. Loss of conciousness occurs only after the body has depleted the supply of oxygen in the blood. If your skin is exposed to direct sunlight without any protection from its intense ultraviolet radiation, you can get a very bad sunburn.

At NASA’s Manned Spacecraft Center (now renamed Johnson Space Center) we had a test subject accidentally exposed to a near vacuum (less than 1 psi) in an incident involving a leaking space suit in a vacuum chamber back in ‘65. He remained concious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained conciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last concious memory was of the water on his tongue beginning to boil.

Aviation Week and Space Technology (02/13/95) printed a letter by Leonard Gordon which reported another vacuum-packed anecdote:

"The experiment of exposing an unpressurized hand to near vacuum for a significant time while the pilot went about his business occurred in real life on Aug. 16, 1960. Joe Kittinger, during his ascent to 102,800 ft (19.5 miles) in an open gondola, lost pressurization of his right hand. He decided to continue the mission, and the hand became painful and useless as you would expect. However, once back to lower altitudes following his record-breaking parachute jump, the hand returned to normal."

References:

• Frequently Asked Questions on sci.space.*/sci.astro (If that doesn’t work, try the text-only version of the FAQ)
  The Effect on the Chimpanzee of Rapid Decompression to a Near
  Vacuum, Alfred G. Koestler ed., NASA CR-329 (Nov 1965).
  Experimental Animal Decompression to a Near Vacuum Environment,
  R.W. Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School of Aerospace Medicine, Brooks AFB, Texas.
  Survival Under Near-Vacuum Conditions in the article "Barometric
  Pressure," by C.E. Billings, Chapter 1 of Bioastronautics Data Book, Second edition, NASA SP-3006, edited by James F. Parker Jr. and Vita R. West, 1973.
  Personal communication, James Skipper, NASA/JSC Crew Systems
  Division, December 14, 1994.

Author: Ken Jenks
Alcatel Altech Telecoms
Phone: (011) 899 6427
Fax: (011) 899 6590

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Hi Tom,

Here’s a reminder to send the e-mail version of Canopus modified to use DOS-compliant file names in the attachments. Also double check whether you sent it MIME or UUENCODED - I received it in the latter form and it’s a bit yukky to unpeel & re-assemble.

Keep well,

Chris Penberthy chris.penberthy@mail.liberty.co.za

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Dear Tom,

I have received your latest newsletter but I don’t have any idea how to decode it. I use Eudora for receiving all my e-mail. If you included a normal attacment ie a text file with a name I could open it and print it with my word processor, but your attachment is an html document (I assume) incorporated as part of the e-mail body. I have tried saving it as a file but I can’t find any way of opening it offline either with Netscape or Internet Explorer (I have both).

What am I doing wrong?

Help please!

Graham grantt@ilink.nis.za

Anyone with bright ideas!!! [ Tom ]

If the front-page looks funny, it is because the site manager hasn’t activated the background graphic yet. The site is simple, and will evolve and standardise over the next few weeks.

The dollop in question being a comet by the name of Hale-Bopp, that just happens to be streaking through southern skies – bliss – what luck – what timing.

We headed out of the city towards the rendezvous as evening approaches – we position ourselves on a north-facing ridge. A golden sunset glows out of a perfect clear pale-blue sky.

Excitement runs high – the light fades – Aldebaran reddens – Orion strides across the sky in all its glory.

All of a sudden there it is – just a smudge at first then we catch our breath as Hale-Bopp steams into view. A cosmic express trail blazing its way through the universe. Enjoy this moment it won’t be back again for 2000 years.

We stand transfixed – words fail us – we’ve run out of superlatives. The diamond studded sky twinkles overhead. Time passes, we pause – look around us and come back down to earth. Two girls all alone in the dark African night – what’s that sound, footsteps coming towards us in the darkness.

Faster than the speed of light, we’re back in the car – hearts pounding we hit the road.

Hale Bopp-a-lula
It’s only rock and ice
But we love you
Yeah Yeah!

Lying between the stars Zeta and Sigma Orionis is the bright nebulosity IC434 and intruding into this is one of the finest examples of a dark nebula, the Horsehead B(Barnard) 33 NGC2063 (RA 5h 39m Dec. -2° 32"). It is quite spectacular in the long exposure plates taken by the 200 inch Hale reflector on Mount Palamar. I have read that it can be seen under a dark sky with an 8" telescope fitted with a hydrogen ß line filter. I have tried with an 8" scope but not having the H ß filter I have used the Meade broad and narrow band filters instead, but to no avail. Walter S Houston saw it with a 5" telescope and Leslie C Peltier with a 6" refractor and a low-power eyepiece. If you try, allow your eyes to dark-adapt for at least 30 minutes and keep Zeta Orionis outside the field.\

The four bright stars of the Trapezium enveloped in the famous Great Nebula (M42) are easily seen with a small telescope and never fail to please. The three brightest were noted by Christian Huggens in 1656 and the fourth in 1684. Two more stars were discovered early in the 19^th century by Otto Struve and Sir John Herschel and towards the end of the century two more very faint stars were seen. The fifth and sixth stars can be seen under good sky conditions with a 3" telescope.

My observer's notebook records dozens of stars and deep-sky objects in and around this fine constellation and paging through them brings back memories of many delightful observing sessions during past summer seasons.

All you need to do is to drop us a line and we will add your name to the list. The committee is appointed by ballot at the AGM. Nominations close on the fourth Wednesday of June 1997.

This also solves the problem of having someone in attendance even though the seeing conditions are poor. Should there be adverse weather on the night, members of the public will not feel too disappointed as they will have the opportunity to attend the other functions on that night.

Please make a note of this in your diary and publicise it as widely as you can. We would be delighted to host hundreds more each year.