The October 2015 edition of MNASSA (Monthly Notes of the Astronomical Society of Southern Africa) is available on line. Below is the title page and list of contents. You may, sickness however, go here, to download the full edition.
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Monthly Notes of the Astronomical Society of Southern Africa
On Wednesday the 09th we set off for Leeuwenboschfontein (visit their website to by clicking here) within minutes of our scheduled departure time. We were quite chuffed, online as we do not often manage to meet our departure deadlines for trips like this. We stopped off at Die Veldskoen Padstal (visit their Facebook page by clicking here) about 4 km north of De Doorns for a light lunch, prescription buying a few bottles of wine and a bag of fresh cherries. For good, friendly service and quality food I can really recommend this place. We have been stopping off there since 2008 and not been disappointed once. At Leeuwenboschfontein we found that the permanent caravans had been nicely enclosed to afford privacy and protection against the wind which often becomes quite chilly in the evenings.
Willem and Iain were already camped on site, Alan and Rose arrived on Thursday and moved into the second permanent caravan, followed by Barry and Miemie who occupied Dalzicht guest house. Johan, Nellie and Dominique moved into the third caravan on Friday and Auke, Chris, Lenelle and Susan, all camping, also arrived during the course of Friday. Joan, who runs the reception at Leeuwenboschfontein, was kind enough to lend us a deepfreeze for the campers to use over the weekend, which was very useful.
Thursday evening everyone socialized at our caravan but the evening was also very good from an astronomy point of view with excellent seeing conditions. Rose and Lynnette went to bed shortly after midnight but Alan persevered until around 02:00. Barry also put in some time with the telescope and camera and, amongst other things produced a beautiful shot of the Tarantula Nebula (NGC 2070 or 30 Doradus). I was up until just before 06:00.
Friday evening saw more socializing in the late afternoon and early evening with the telescope work taking place later on and after midnight. The seeing was very good. Early on Auke and Barry remarked that one could walk away from the group around the fires and, without too much effort and hardly any dark adaptation, see 47 Tucanae (NGC 104), Omega Centauri (NGC 5139), the Jewel Box (NGC 4755), Eta Carinae, the Southern Pleiades (IC 2602) and the Andromeda Galaxy (M31/NGC 224).
Readings were taken with the Unihedron Sky Quality Meter (visit their website by clicking here to find out more) on the 09th, 10th & 11th and the average of 20 readings on each night was 21.70, 21.69 & 21.58 (Magnitudes per Square Arc-Second or MSAS) respectively. This converts NELM (Naked Eye Limiting Magnitude) values of 6.4816, 6.4772 & 6.4168. Using the Loss of the Night application and viewing 30 stars, at the same time as taking the Sky Quality readings, gave a limiting magnitude of >5 ± 0.1 on all three occasions.
On Saturday the weather closed in and light rain fell so observing was out as was the customary braai under the stars. Fortunately Leeuwenboschfontein has a very nice enclosed central lapa for just such occasions. We spent a pleasant evening there, out of the wind and rain and warmed by the braai-fires. Alan opened a bottle of sparkling wine to celebrate he and Rose’s wedding anniversary, which was the following day, so it really was a festive occasion. Later in the evening Snorre managed to attract a lot of attention by climbing a tree that proved difficult to get out of but, once everybody had stopped making a fuss, he did what cats normally do; climbed down on his own.
Sunday was overcast too, but most people had planned to leave on Sunday in any case. Chris left early, followed by Johan, Nellie and Dominique and then Lenelle and Susan. Alan and Rosemary left just after lunch and Auke, who had intended staying until Tuesday, also decided to leave because the weather forecast did not look promising, from an astronomical point of view, for the next two evenings. In any case he had a pile of calendars to pack. Before Auke left we looked over the facilities being prepared in the large shed adjacent to De Oude Opstal guest house and they look very promising indeed. With only Willem, Iain, Lynnette, Snorre and I in the camp and Barry and Miemie in Dalzicht Leeuwenbosch was suddenly very quiet. On Monday Barry, Miemie and the Fosters packed up, said goodbye to Joan and to Leeuwenboschfontein and left the camp to Iain and Willem.
We arrived home safely and started the dreaded unpacking and packing away to wrap up our final visit to Leeuwenboschfontein for 2015, but we will be back in 2016. We did not make use of the stargazing enclosure next to the runway this time because there were very few other people in the camp so we could control the lights. A problem with the water supply has also resulted in the grass dying inside the enclosure so it would have been very sandy and dusty in there. Johan snr has promised the grass will be back in 2016 and so will we, hopefully on a regular basis.
In support of the efforts currently underway to document the history of the Royal Observatory a lot of historic material has been made available in digitized form by Auke Slotegraaf. While attempting to work my way through this formidable volume of information I came across the following in Royal Observatory, Cape of Good Hope, 1875 (iii).
“The “meridian mark” referred to in Table III, is on an undulation immediately to the east of the mountain called Blaauw Berg, and is situated some 13 miles north of the Observatory. It is a pillar built up to serve as a permanent meridian mark for the 10 feet Dolland’s Transit. The transit instrument is about 512 feet west of the meridian of the Transit-circle. The azimuth of the mark from the meridian of the Transit-circle, assumed in the determination of the azimuthal errors given in Table III, has been 2’ 40” west. It would appear that the assumed azimuth is too great by about 1”.3, and that the true azimuth of the mark is nearly 2’ 38”.7 west. The azimuthal errors derived from the position of the mark have not been used in the reductions, except for the approximate determinations of the clock error for time-ball purposes. The mark can only be well seen near noon on rather cloudy days; on bright, clear days it can only be observed soon after sunrise and near the time of sunset. The value of the mark as an indication of changes in the position of the Transit-circle, is not so great as it would be were observations possible at any hour of the day.”
So where was this meridian marker? After several e-mails between Auke Slotegraaf, Dr Ian Glass and I, it soon became clear that this specific object had not been seen by any members of the astronomical fraternity for many, many years. Ian produced correspondence dating back to 2012, in which a Mr. Seymour Currie, verified that that the object was in fact on his farm. The correspondence was conducted via the staff of Cape Nature at the Blaauwberg Nature Conservancy, and no mention was made of the farm’s name. Not knowing the farm’s name becomes a crucial point as the story develops.
I sent an e-mail to Mr. Currie who promptly phoned back. He had no objections to us coming to view, measure and photograph the meridian mark and he agreed to phone back again with instructions on how to get to his farm and an evaluation of how difficult it would be for us to get right up to the meridian mark. By Saturday morning, the 05th of December I had heard nothing from Mr. Currie and all telephone calls were answered by the dreaded voice message, “The subscriber you have dialled is not available ……”.
On the 05th a party consisting of Auke Slotegraaf, Chris Vermeulen, Dr. Ian Glass, Chris de Coning, Johan Brink, Kechil Kirkham, Dirk Rossouw and I, assembled at the Observatory. We were confident that, thanks to previous efforts by Ian and the help of Google Earth, we had the position pinned down and it looked as if there were useable access roads, but we were all anxious to hear from Mr. Currie.
The first task though, was to get up onto the roof of the Observatory building and try and see the meridian mark from there. Unfortunately the Eucalyptus trees that had been planted over the years successfully cut of, not only any possible view of the marker, but of the entire Blaauwberg. I had still not been unable to raise Mr. Curry on the phone so we decided to go with Google Earth and Google Maps and the coordinates of the marker. The route seemed pretty straight forward but Dirk several times expressed concern that we were venturing well of the beaten track and he had prior experience of the fact that Google did not take cognisance of fences and assorted farm gates in out of the way areas like this. In the absence of any communication from Mr. Currie we had little choice but to set off, guided by Google.
One section of the party, Auke, Kechil and Johan would stay behind and find a spot near the bird hide, at the northern extremity of the Observatory property, from which they hoped to observe the other section’s arrival at the marker. Chris dC had to first make a delivery and would join us later guided by Google. Chris V and Ian took the lead followed by myself and behind me Dirk. Somewhere on the N1 I lost sight of Dirk behind me but it turned out he had made a detour into Century City to refuel. I also lost sight of Chris V and Ian ahead of me but I had the Google turnoff from the N7, Frankdale Road, memorized so I was confident I would not get lost. I found the turnoff and after 1.3 km the tarred surface gave way to a track which became progressively worse, slowing me down to walking pace for long stretches. About 4.2 km from the N7, Zonnekus Road links up with Frankdale Road at a T-junction. There is a large, imposing, locked gate and, much to my surprise, parked on the other side of the gate were Chris V and Ian. While I was explaining to them how to get to where I was, Dirk pitched up, on my side of the gate. Chris V and Ian headed back to the N7 and Dirk and I waited. While we were waiting Chris dC arrived, also on the wrong side of the gate! More explanations and he also retraced his steps. After Chris V, Ian and Chris dC joined us Dirk once more voiced his concern that, although we were headed in the right direction, we might run into the Blaauwberg Nature Conservancy fences before reaching our target. Our cell phone signal had faded on us shortly after leaving the N7, so we were unable to update Google maps or try Mr. Curry again.
Off we went once again with Chris V and Ian in the lead, followed by Chris dC, then myself with Dirk bringing up the rear. Just over three km after leaving the gate, we encountered the gate and game fence of the Blaauwberg Nature Conservancy, as predicted by Dirk. Ian and I walked along the fence for quite a way trying to find higher ground on order to get a better view of the area where we thought the marker was and eventually we thought we had it. Unfortunately it was a case of so near and yet so far. After some debate we decided to call it a day and head home. I had to refuel as I did not have enough to get me home to Brackenfell and Chris dC very kindly offered to follow me to the filling station in Killarney in case I ran out of fuel completely. So we said our goodbyes and off we went.
After filling up in Killarney I parked the car and had a sandwich while going over the day’s events and checking that Mr. Currie had not tried to contact me. The more I thought about the day’s events the more I felt that Dirk had been right after all and we should have tackled this expedition from a farm called Blaauwberg on the northern slopes of the mountain. By now everyone else was well on their way back home or back to the Observatory, so I set of on my own. On the farm Blaauwberg I found that the owner was none other than Mr. Curry! It turned out that he and Willem Steenkamp had been very busy out in the veldt that morning planning the Battle of Blaauwberg Commemoration scheduled for the 09th January 2016.
After coffee we set off to the marker. Mr Curry and his wife took a quad-bike and I followed in their 4×4 all the way up to the marker, accompanied by their two magnificent Ridgebacks, racing along with the vehicles. The first kilometre after one leaves the farmyard is fine and can be attempted in any vehicle but the next just over one kilometre is uphill, sandy and riddled with mole tunnels. I would not venture up there in anything but a 4×4 vehicle.
Anyway, there the marker was and, after my hosts departed, I set about measuring and photographing. Both tasks were complicated by the fact that three sides of the marker were overgrown with very thorny bushes reaching almost to chest height. A section, which I think was added at a much later date than the original construction, has come off the top of the marker. The reason I think it is a later addition is that the cement looks quite different from that used in the construction of the marker and also, the removal does not seem in any way to have damaged the top of the marker. The marker is not, as stated in the reference at the end of this post, 14 feet (that’s over four m) high.
Mr Curry reports that up to about 10 years ago the military actually come round once a year and cleared away the brush around the marker but that no longer happens, as I can testify. It was not only the surrounding bush that made photography difficult but also the fact that the sun was fairly low in the west, which caused all sorts of complications with shadows. After finishing up I drove back to the homestead, reluctantly handed back the 4×4, said my goodbyes and headed home.
The Curries say that during military exercises with helicopters, it appears as if they fly to a point directly over the marker and then change course. Perhaps somebody could investigate this because it would be interesting to know if the marker is in fact used as a beacon, why and since when.
Dr Glass has also tracked down two more references to the meridian marker which seem to pinpoint its construction to August 1841. The references are to be found in Verification and Extension of La Caille’s Arc of Meridian at the Cape Of Good Hope by Sir Thomas Maclear. Vol 1, Published by order of the Lords Commissioners of the Admiralty, 1866.
Page 403: “Having obtained permission on the 10th of August, 1841, from the trustees of Dirk Gysbert Kotze, to erect a pillar on the Blaauwberg estate, on a hill south-west of his dwelling house, in the meridian of the transit room of the Royal Observatory, a party was told off for this service shortly after the return from the measurement of the Base. The pillar is a truncated pyramid 14 feet high, constructed of stone and lime masonry, cased with Roman cement.
By observation of the consecutive transits of circumpolar stars in the winter season made with the 10-feet transit instrument, the azimuth of the centre of the pillar is 179° 59’.57”, reckoning from the south round by the west; and by triangulation its distance is 68415 feet, or nearly 13 miles north of the transit instrument.”
Page 444: “The position of the pillar is on the undulation, immediately to the east of the mountain named Blaauw Berg, distant nearly 13 miles north from the Royal Observatory. The pillar was built to serve as a permanent meridian mark for the 10-feet transit instrument; also for obtaining the azimuths, by direct angular measurement of the trigonometric points, that are visible from the Observatory.”
The Carina Nebula is about 7500 light years away in the direction of the Carina constellation. Carina was originally part of a very large constellation Argo Nevis but Nicolas de Lacaille divided it into three new constellations in 1763, see Carina (the keel), Puppis (the poop deck) and Vela (the ship’s sails). It is also known as NGC 3372 and was discovered in 1751 by Nicolas Louis de Lacaille, while observing from the Cape of Good Hope. It is a colossal emission nebula about 300 light years wide that contains extensive star forming regions. A very interesting object in the Carina Nebula is the Homonculus Nebula which is a planetary nebula that is being ejected by a luminous blue variable star, Eta Carinae (shorthand ? Carinae or ? Car). This star is one of the most massive stars known and has reached the theoretical upper limit for the mass of a star and is therefore unstable. The instability results in periodic outbursts during which it brightens and them fades again. During one such outburst between the 11th and the 14th of March 1843 it became the second brightest star in the sky but then faded away. Around 1940 it began to brighten again, eventually peaking in 2014 but not achieving nearly the levels of brightness seen in 1843.
Leslie Rose is one of the regulars who attend the Southern Star Party and the photograph featured here, was taken by Leslie. The first SSP he attended was in March 2011 when Leslie had neither telescope nor camera!