For those of you who have never been to ScopeX or even considered going or, worse still, never heard of it, you really need to do something about it. On 16 September, the 16th annual ScopeX event will be held at the Military History Museum in Johannesburg.
This is ASSA’s premier outreach event, so please remind all friends, family, colleagues, etc. who may be interested, to not only come but to also pass on the news within their sphere of influence. Full details can be found on the website: – PDF flyers and posters can be downloaded from the front page.
There is a full programme of interesting lectures, exhibits, and activities, suitable for people of all ages. The museum is great for a family outing, as are the Zoo next door and the Zoo Lake park around the corner. The evening star party (weather permitting) is also very popular.
To all the amateur telescope makers, astrophotographers and observers, please bring examples of your work to display. Even if you have shown the stuff before, remember that there are always newcomers who have not seen it, and others would like to see it again. Work in progress, no matter how humble, is just as valuable to exhibit as a finely finished product, so that people can understand the process and get ideas. You may even win a prize for your efforts!
Check out the excellent range of items to be won in the raffles. Given the limited number of tickets, your chances are really good.
At the February 2017 Southern Star Party (Go here to read more about this event) Deon and Ronelle Begemann unveiled their binocular stand. It is basically the standard parallelogram design but it is very affordable, very easy to put up and it works superbly well and would make an affordable addition to any astronomy enthusiast’s equipment. This is a photo review of the apparatus and for more details and a price, you must contact Deon directly.
Thursday required an early start to beat the infamous N1-traffic and have breakfast at the Rcafe in Long Street (go here to find out more) before starting our day. We left Brackenfell at 05:17, which was actually later than our original ITD of 05:00. ITD? My shorthand for Intended Time of Departure. We were parked in front of Rcafe by 05:45 which meant that the trip had taken us a mere 28 minutes. As soon as the doors opened at 06:00 Lynnette and I went inside to order two much needed Americano’s to start the day properly. What really amazed us was that the owner and staff recognized us the moment we walked in the door and it was a few days more than a year since we’d last been there! Auke arrived shortly after us and ordered his cappuccino. After breakfast, we headed for the Iziko South African Museum (click here for more information) where Benjamin was waiting to unlock the gates for us and set out the traffic cones to prevent vehicles entering our display and observing space in the amphitheatre. The weather was clear but blustery. The wind was, in fact, such a nuisance that I eventually took down and put away the posters, as the frames were being badly scratched every time they toppled over onto the brick paving. Anyway, by 08:00 we were ready to roll and all we needed was a visitor or two, which we soon got.
Thursday’s are popular school days at Iziko and we had three groups that we managed to convince that they should take a peek at the Sun. There were several other school groups whose teachers waved us away when we invited them to view the Sun. Being a weekday many of our visitors were from outside the country’s borders as most South Africans were hard at work earning an income. Many of the tour guides with the groups declined to let their tourists take a look at the Sun. Their reason was mostly that they had a schedule to keep to and did not have the time. Nevertheless, we had groups from Gabon, Thailand, Hong Kong, France, Netherlands, Israel, and Germany.
It was also nice to have the research staff from the backrooms of Iziko pay us a visit. I was especially pleased to make the acquaintance of Jay van den Berg a palaeontologist on Dr Roger Smith’s staff and Clair Browning the newly appointed Curator of the Karoo Collection.
The problem of getting people to sign our visitor’s book was highlighted for the umpteenth time. Many people who viewed the Sun through our telescopes flatly refused to sign the list and some actually became quite agitated when asked to do so. This problem is exasperated when one is busy and you simply do not have time to chase after people and ask them to sign. So, once again, our signature total (288) and counter tally (597) do not agree. I am more convinced than ever that the answer lies in devising a means to automatically count the number of people who look into each telescope’s eyepiece.
Because the Sun appears as a very bland and uninteresting white ball as a result of of the solar filter fitted to Lorenzo, many viewers say it looks like the Moon. So I decided to do some experimenting with filters to make the image more “exciting”. The images were all taken with my mobile and I am afraid that I do not have the world’s steadiest hand, so the photos are not of the best quality.
Sunday was an almost perfect day for an outreach event in the amphitheater of the Iziko South African Museum (click here for more information) in Cape Town. Lynnette and I, unfortunately, got there a bit later than we had intended. Auke had almost finished setting up by the time we arrived and we just managed to get Lorenzo setup before the first visitors put in an appearance.
While we were setting up, Benjamin, the museum security guard, came round to say hello and put out the traffic cones thereby preventing people from attempting to park among the telescopes. Throughout the rest of the day, he appeared every now and again, keeping a watchful eye on the ever present idlers and strollers who often have less than honest intentions.
We had a steady stream of visitors throughout the day. However, every time a tour group passed through the activity around the telescopes peaked and required all hands on deck. It was really a pity that, other than one lone sunspot (2670) which was about to disappear over the rim of the sun, there was no activity to be seen. I found the overseas visitors far more aware of astronomical matters than the South Africans. Having said that though, Lynnette had one local three-year old who knew the names of all the planets and, when quizzed, also knew which planet was the smallest and which was the largest!
All in all, it was a very pleasant day with the wind dying down by mid-morning and the few clouds that there were never really posing a serious threat to our solar observing. One of the problems, that occurs every year, with this kind of event is the effort to get people to sign our visitor’s register. Some people just refuse point blank and others again refuse to give contact details. During periods of high activity, when everyone is manning a telescope, we also lose signatures because there is nobody available to monitor if visitors sign the register or not. Our counters, as is usual, gave far higher figures than the number of signatures but, because one is busy with visitors, one probably also misses visitors with the counters. Maybe we should get some inventive person to install a counter at the eyepiece that counts when people look into it.
Thursday was a very different kettle of fish at the Brackenfell Public Library compared to Tuesday. No sun, lots of low gray clouds and a cold, blustery north-westerly wind. We implemented plan-B and moved inside, as discussed previously with the library staff. Amanda helped us get organized in the library hall and pointed out the spots in the foyer we could use for posters and A-frames.
Despite putting up notices inviting people to come and flummox us with their astronomy queries we had the grand total of two visitors the entire morning. Those two were actually old friends, Billy and Halcyone Brits who had heard that we would be there and come specially to see us.
The afternoon wasn’t much better as the cold weather seemed to have thinned out the number of learners quite drastically too. Following Lynnette’s suggestion, we gave a talk to the small group that was there. This talk was one we had previously compiled with input from the staff at Boesmansrivier Primary School for use with their learners. The talk was quite enthusiastically received by the learners present. Their enthusiasm was, in fact, at times more than just a bit rowdy!
Murphy saved his final trick for the end of the day. When we tried to start the Vito and leave for home it refused point blank. Not too much of a problem as I had a spare battery at home. We phoned a friend who nipped round, picked me up and dropped me at home. I picked up the spare battery, popped it into the boot of the Polo, and headed back to the Library where Lynnette was waiting.
Murphy now played his next trick. The new battery was about one millimeter too large to fit into the battery compartment of the Vito and the battery leads were too short to reach the battery in any other place outside the battery compartment, where we would be able to shut the door. Lynnette and I quickly ran through plans C to Y before I hit on plan-Z. I connected the spare battery and, while I was holding it, Lynnette started the Vito. Lynnette then kept the engine running quite fast and I disconnected the spare battery, connected the old battery, and slid that into the battery compartment. It all worked perfectly without any shocks, sparks or short-circuits. I was very careful not to throw a clearly crestfallen Murphy the middle finger as he has a very long memory.
Lynnette drove the Polo home and I followed in the Vito, finally bringing the day to a close.
We set up just outside the entrance to the Brackenfell Public Library. The forecast said it would be a sunny day so we also put up our gazebo and decorated that with some of our banners. The banners look nice, provide added wind protection, make the gazebo sturdier and also help prevent uncontrolled access. Sunelle, Lötter and her staff used the material we gave them, predominantly from our own stocks, to put up displays in the entrance foyer and several other parts of the library
As we have experienced in the past it takes a lot of effort to get the public to come and take a look, despite the fact that the telescope was very visible, as were our A-frames and pull-up banners. One has to resort to accosting people, as they approach the entrance and begging them to come and take a peek at the Sun and its lonely sunspot.
This all changed dramatically during the afternoon when the schools closed; we were almost inundated! The Library serves as a focal point for learners whose parents are at work as they also use the library hall to do their homework. The youngsters from the apartments across the road from the library simply use the library and environs as an entertainment area. For the latter group, our presence was a welcome added attraction to their normal routine.
Thanks to the sunny weather and the eager learners it was eventually quite a pleasant and productive outing.
Lynnette and I set up Lorenzo in the rooftop parking area of the Family Pick & Pay on the corner of Old Paarl Road and H.O. De Villiers Street in Brackenfell. The event had been advertised via local social media sites and announcements were also made by the store manager during the course of the evening.
The turnout was disappointingly low but the few people that did turn up were very enthusiastic, which compensated for the poor attendance.
On the 16th of July 2017 Leeuwenboschfontein had a light sprinkling of snow and the staff there were kind enough to send us some photos.
Leeuwenboschfontein is situated in the Western Cape on the very western edge of the Little Karoo at an altitude of just over 1 000m. It is a fantastic place for stargazing and observing and was the venue for the thirteenth Southern Star Party held in February 2017 (more about that event can be found here). We are already planning the 14th Southern Southern Star Party scheduled for October 2017.
Anja Bruton, the Science Promotions Coordinator at SKA Africa, approached StarPeople to accompany the NSTF Brilliants group (http://www.nstf.org.za/youth/brilliants-programme/) on the tour to the SKA and SALT and we jumped at the opportunity. Anja and Dimpho would fly to Kimberly to meet up with Jansie Niehaus and Wilna Eksteen from the NSTF (http://www.nstf.org.za/) and a group of students, chosen for their exceptional performance in the 2016 Matriculation exams; specifically in the Science paper. This group would fly down from Gauteng and, after a day’s sightseeing in Kimberley, they would tackle the long journey to Carnarvon in two Quantums on Saturday the 24th. They would also be accompanied by two photographers who were tasked with documenting the trip.
Lynnette, Auke, Snorre and I would leave Cape Town for Carnarvon (https://en.wikipedia.org/wiki/Carnarvon,_Northern_Cape) early on Thursday the 23rd and book in at the Lord Carnarvon Guest House. Anja and the rest of the group were scheduled to arrive shortly after lunch on Saturday and on Saturday evening StarPeople were to present a stargazing session at Klerefontein, the SKA’s operational base about 15 km outside Carnarvon. On Sunday morning the group would visit the SKA site itself and after that, e would depart for Sutherland. On Sunday evening there was to be stargazing session at the SAAO’s Visitor’s Centre and on Monday morning we would tour the SAAO facilities on the hill before heading for Cape Town.
However, as Robert Burns once said “The best laid schemeso’ mice an’ men / Gang aft a-gley.” First of all, Auke had to pull out because of domestic complications. Then the car hire company notified us that the vehicle we required could only be delivered on Friday morning and not on Thursday afternoon as requested. This, of course, scuppered our 05:00 departure plan, but Lynnette and I made sure that we had everything packed and ready to load by 08:00 when the vehicle was scheduled to arrive. However, it only arrived at about 08:30 and, when it did arrive, it was petrol and not diesel driven as had been requested. Disaster! Petrol-driven vehicles are not allowed access to the SKA site because their spark plugs generate interference for the radio telescope. It is more than 600 km to Carnarvon and we had to be there before dark. We also still had to load the vehicle so, if we sent it back and insisted on a diesel driven one, there was no chance of reaching Carnarvon before dark. We signed for the vehicle, finished loading in record time and at 09:40 we set off for Carnarvon.
The journey was long but uneventful. We stopped for petrol and Lynnette’s packed lunch in Vanrhynsdorp (https://en.wikipedia.org/wiki/Vanrhynsdorp) after 290 km. We then stopped halfway up the spectacular Vanrhyns Pass to take pictures. The original pass was constructed in 1880 by Thomas Bain and climbs almost 600 m from the Knersvlakte to its summit, situated at just over 800 m, which is about the same as the top of Du Toitskloof pass. The pass has an average gradient of 1:15 with the steepest section being 1:12.
On the last stretch, we had to push it a bit and reached Carnarvon in the gathering dusk at 17:45, where we reported to Pieter Hoffman at the Lord Carnarvon guest house in Daniel Street (https://www.carnarvon.co.za/lcindex.htm). This building was the Officer’s Mess during the Anglo-South African War and he has done a magnificent job of restoring it. We unloaded, got Snorre settled in, and walked round to Lord’s Kitchen in Victoria Street (https://www.tripadvisor.co.za/Restaurant_Review-g4226745-d8743616-Reviews-Lord_s-Carnarvon_Northern_Cape.html), also run by Pieter, for supper. After supper, we walked back to the Lord Carnarvon and had the amusing experience of being escorted by a police vehicle because “nobody walks around Carnarvon in the dark”. This remark struck us a rather odd considering the fact that there were quite a few other local people in the streets.
On Saturday morning, after breakfast at the Lord Carnarvon, Lynnette, Snorre and I took to the streets to do some house hunting in case we should decide to move to Carnarvon. The results of this expedition were rather disappointing as we soon discovered that, like many small country towns in South Africa, the homeowners wanted lots of cash for the property that was, in our opinion, worth a lot less. The other aspect which surprised us, even though Anja had warned us about it, was the negative sentiment toward the SKA project and the amount of disinformation circulating in the town. This varied from stories that farmers were being chased off their farms without compensation or that farms were being confiscated in order to distribute the land to previously disadvantaged persons, and even that townsfolk were to be evicted so that four blocks of houses could be knocked down to build a college. We also came across an openly hostile sign in a back yard in Kidd Street. Most obvious was the fact that almost everyone we spoke to had no bloody clue what the SKA was, or what it was about.
Shortly before 16:00 Anja let us know they had arrived and were having a late lunch at Lord’s Kitchen. We popped around and Anja introduced us to the group. After the meal the group dispersed to their various rooms and Anja, Dimpho, Lynnette and I set off for Klerefontein, the SKA’s operational base, to set up Lorenzo for the stargazing later that evening. Mission accomplished we headed back to town to collect all our warm gear and have supper. After supper, the five vehicle cavalcade made its way back to Klerefontein. On a hill southeast of where we were situated was the large 7,6 m dish of the C-BASS radio telescope (https://www.ska.ac.za/science-engineering/c-bass/) catching the last rays of the setting sun as it patiently toiled away sweeping back and forth to map the radio sky in the 4,5-5,5 MHz frequency range. The C-BASS dish, recently moved from Hartebeeshoek (http://www.hartrao.ac.za/) to Klerefontein, is the southern component (the other telescope is in California) of a project to produce a microwave (short-wavelength radio) radiation map similar to the one produced by the European Space Agency’s Planck satellite (https://en.wikipedia.org/wiki/Planck_(spacecraft)), but at longer wavelengths than Planck. C-BASS will also measure the polarization of the radiation.
Anja split the students into two groups for the planned activities. One group stayed with Lynnette, Lorenzo and I to do some stargazing. The other group went inside to participate in Skype Q&A session with Jim Adams, Deputy Chief Technologist at NASA (https://solarsystem.nasa.gov/people/adamsj).The Milky Way was magnificent and drew many Ooh’s and Aah’s from the group. I did a basic what’s-up-tonight and then kept talking while Lynnette operated Lorenzo. There was no Moon but fortunately, Jupiter and Saturn were nicely placed and we could also show them a selection of the other well-known objects. After about an hour the groups changed around and Lynnette, Lorenzo and I repeated our earlier performance. Once we had done with the second group, it was packing up time and then back to town for a hot shower and some much-needed sleep.
Sunday morning at 06:15 it was breakfast time at Lord’s Kitchen and, after collecting our packed lunches, it was all aboard for the trip out to Klerefontein where Anja gave us a Health and Safety briefing and had us all fill in indemnity forms. During the briefing, the emphasis was placed on the mayhem electronic devices caused for the radio telescopes. Mobile phones, which all had to be switched off, were a prime source and even my hearing aid’s hands-free device, that uses Blue Tooth, had to be switched off. After all, this had been sorted out, our motorcade tackled the more than 70 or so kilometers out to the actual SKA site. Large sections have already been tarred, but there are still fairly long sections that are very rough and dusty. Lynnette and I had to leave our petrol driven vehicle with Snorre in it just inside the checkpoint at what used to be the Meysdam farmhouse and continue with Anja and Dimpho in their vehicle. Snorre was quite safe, with enough fresh air, water and food to keep him busy till we get back. We made sure that the vehicle would be in the deep shade while we were away too.
Our first stop was the very impressive, half underground, Karoo Array Processor Building. Placing the centre below ground level was essential to minimize the amount of interference from the computers. In addition to being below ground level, the whole installation is housed inside a huge Faraday cage (https://en.wikipedia.org/wiki/Faraday_cage). It is ironic that a radio telescope, which cannot function without massive computer support, also experiences its most annoying interference from computers. It was while touring the Processor Building point that I realized that, if I had simply put my phone on Airplane Mode, I could have brought it with me and taken photographs. Some mothers are just unfortunate to have very dense children! Our next stop was the huge, hanger-sized building where the MeerKAT dishes are assembled. It is only when one stands next to one of these huge constructions lying flat on the floor that one really gets an idea of their overwhelming size. Needless to say, at this point, I mentally administered several more resounding kicks to my posterior for not having anything to take pictures with. After completing this part of the tour it was back into the vehicles for the drive out to the telescopes.
The first stop was the KAT-7 dishes (http://www.ska.ac.za/) where all but one pointed south, collecting data on some unseen object light years away in a distant part of the Universe. KAT-7 was a precursor engineering test bed for the larger MeerKAT array and also served as a demonstration of South Africa’s technological ability when the bid for the Square Kilometre Array (SKA) was submitted. However, KAT-7, the first radio telescope ever to be built with a dish consisting of composite material, is also a science instrument in its own right. Each 12-meter dish is fitted with a prime focus receiver and a Stirling pump cooling unit that supplies the cryogenic cooling to keep the electronics at 75 K. The total collecting area of the seven dishes is about 2000 m2 and they function in the 3 to 30 cm wavelength range at frequencies between 1 200 and 1 950 MHz. KAT-7’s minimum baseline (shortest distance between two dishes) is 26 m and the maximum baseline (longest distance between two dishes) is 185 m. These seven dishes will eventually be decommissioned as science instruments when their successors, the MeerKat Array, comes online and be made available for serious amateurs.
Then we were off to find a MeerKAT dish (http://www.ska.ac.za/) that was positioned in such a way that it would be easy to photograph, which wasn’t easy because, despite the fact that they were lots of them, they were all facing in different directions. It really is an impressive sight, seeing these dishes scattered across the Karoo veldt against the backdrop of the low, dolerite topped hills that surround the area, with the dolerite providing a natural radio screen for the telescopes. Considering that only half of the MeerKAT dishes have been erected so far, one can only imagine what a spectacle it will be when all 64 MeerKAT dishes have been completed. The final Karoo Array Telescope or KAT will definitely be a must-see destination and a breathtaking spectacle for all who visit it. MeerKAT will eventually form the core of the KAT radio telescope array. These 13,5m dishes differ from those of KAT-7 in that they use an offset Gregorian configuration for the placing of the secondary dish and the receivers. Each dish is equipped with three receivers; 0,58 – 1,015 GHz, 1 – 1,75 GHz and 8 – 14,5 GHz. The MeerKAT minimum baseline is 29 m and the maximum baseline is 8 km.
Both KAT-7 and MeerKAT are entirely South African conceived, funded and built enterprises and, even after the construction of the KAT, which has multiple international partners, these two installations will remain entirely South African.
Our next stop was the Hydrogen Epoch of Reionization Array (HERA) (http://www.ska.ac.za/) which is the simplest construction imaginable and is the successor to the Precision Array for Probing the Epoch of Reionization (PAPER). PAPER has 128 antennae situated at the SKA site and 32 antennae situated in West Virginia in the USA. HERA is an American, British and South African collaboration that will eventually have 331 antennae of 14 m each at the SKA site. The existing PAPER installation will be moved to a location slightly west of the HERA installation and eventually decommissioned when HERA is fully operational. Whereas KAT-7, MeerKAT, and KAT are multipurpose installations HERA has only one fixed goal; it is going to probe back into time to try and find that moment when the very first stars switched on to light up in the Universe. In the process, it will produce a three-dimensional map of the universe during that specific period using radio waves in the 100-200 MHz frequency range. This project is the radio astronomy equivalent of the Laser Interferometer Gravitational-Wave Observatory (LIGO), and when they succeed, this project could very well be in line for a Nobel Prize. The antennae are fixed in one position, pointing straight up at the sky and have no moving parts, which greatly reduces the cost of the installation. What makes this project remarkable is that it is constructed with materials bought off the shelf in a local hardware store by people from the local community of Carnarvon who have been trained by SKA scientists. The big dishes of KAT-7 and the even bigger dishes of MeerKAT look like science instruments. HERA, however, looks like an inverted chicken coop or perhaps some sort of landscape art and not very scientific at all.
We went back to the Processor Building to enjoy our packed lunches and, while there Lynnette noticed that one of the Quantums had a flat tyre, necessitating a wheel change. After lunch, Anja and Dimpho dropped Lynnette and I off at Meysdam to pick up our vehicle and then we all traipsed back to Klerefontein where Anja and Dimpho changed vehicles before we all drove back to Carnarvon to refuel. Lynnette and I had done that the previous evening so we just hung around until the whole convoy was ready to start the long journey to Sutherland, which Anja had elected to do via Loxton (https://en.wikipedia.org/wiki/Loxton,_Northern_Cape). The just under 70 km from Carnarvon to Loxton was a breeze on a nice tarred road but then came the long 100 km grind on the R356 gravel road to Fraserburg (https://en.wikipedia.org/wiki/Fraserburg). We had been contemplating a visit to the palaeosurface at Gansefontein, just outside Fraserburg, but time was against as; seriously against us. We had hardly left Fraserburg when the sun set and, as it got darker, driving became more and more difficult. The 110 km stretch to Sutherland (https://en.wikipedia.org/wiki/Sutherland,_Northern_Cape) was going to take much, much longer than planned and our stargazing appointment at the SAAO site (http://www.saao.ac.za/about/visting/sutherland/) outside Sutherland had to be canceled. Because Lynnette and I were the last car in the convoy, we collected all the dust from the four vehicles ahead of us. This forced us to fall back more than a kilometer behind the fourth vehicle before we had a clear view of the road ahead.
We all made it safely to Sutherland and, while the majority of the group was booking into the Sutherland Hotel (http://www.sutherlandhotel.co.za/accommodation.php), Lynnette, Snorre, Anja and I as well as the two drivers of the Quantums, booked into Kambro Kind Guest House, where we were welcomed by Juanita Hutchings. Once booked in we went back to the Hotel where we had a typical Karoo supper consisting of meat, meat and more meat with a few vegetables right at the end of the buffet table. It is just a pity that the hotel did not think of having a nice fire going in the dining area on such a cold evening.
After supper Lynnette and I, Lorenzo, Anja, the photographers and several students drove out to Middelfontein to do some stargazing (http://www.roomsforafrica.com/establishment.do?id=13879&gclid=Cj0KCQjws-LKBRDCARIsAAOTNd6cUH9fdKlh5bbYksnV0F5D-BQPK4kMRrO8IdxP7D_a6uSOZX_UQX8aAoUUEALw_wcB). The photographers were spending the night on Middelfontein, but the rest of us would have to drive back to town to get some sleep. The right side sliding door on our vehicle, which had been playing up since the previous day went on strike when we started unloading. It first refused to open and then, when we forced it to open, it refused to shut without the use of considerable force and, once shut, it refused to open again so we left it shut. Then the courtesy light inside the door which was supposed to only go on when the door was open, decided it wanted to be on even when the door was shut. A resounding thump on the outside of the door convinced the light to go off and stay off. Once that was sorted out we could get round to the stargazing which was a presented in the same format as on Saturday evening at Klerefontein and, once again, worked very well. So well, in fact, that Anja had to chase us all off to bed around midnight.
On Monday morning Lynnette and I packed up before breakfast and, true to Sutherland’s reputation of being very cold, the windscreen of our vehicle was thickly frosted over and the fishpond had a layer of ice over it, thick enough to walk on. After breakfast at Kambro Kind, everyone gathered at the Hotel before departing for the SAAO site where the group spent some time examining the displays in the Visitor’s Centre before Anthony Mitas took us under his very capable wing and shepherded us up the hill to start our tour at the Southern African Large Telescope or SALT (http://www.saao.ac.za/science/facilities/telescopes/salt/). SALT is an international collaboration between South Africa and several overseas partners and is operated as a separate research entity on the SAO site.
Anthony presented a most comprehensive and informative talk to the group and, to everyone’s delight, arranged to have the 32-ton behemoth raised on its air cushions and rotated for us. After SALT we went to the 1,9-meter telescope. This is the second largest optical telescope in South Africa and, as the Radcliffe Telescope, it used to be housed in Pretoria but uncontrolled light pollution chased it south in the mid-1970’s (http://assa.saao.ac.za/sections/history/observatories/radcliffe_obs/). It has since acquired new instrumentation designed and built by SAAO-staff and still has many years of valuable scientific life ahead of it. At the telescope, we were met by Dr. Potter, a senior astronomer on the SAAO staff. Dr. Potter talked most informatively about the telescope and his own work as well as the other projects being conducted on the telescope. He also demonstrated how easy it was to operate the telescope, especially after the installation of modern electronic control systems, and showed the group around the control room as well.
After saying goodbye to Dr. Potter and Anthony, we stopped off in Sutherland to refuel and then made a beeline for Cape Town where the group had an 18:00 appointment at the SAAO headquarters in Observatory. We made one stop at the Veldskoen Farm Stall and said our final goodbyes before splitting up.
My only regret is that with the group split over several vehicles it was impossible to do any guiding while en route. Although we considered stopping the vehicles at points of interest, it would not have been practical from a safety point of view. Time constraints, which played an important role during the trip, virtually canceled the possibility of additional stops even if safety had not been an important consideration.
I will post more photos at a later stage as they become available from other people who were on the trip as well as the two official photographers.
This Unihedron Sky Quality Meter (Ser. No. 5739 / Mod. 2.17) has been used over a six-year period at various venues in South Africa. I noted that the first four to six readings in every series of measurements we took drifted lower before stabilizing. My revised operating procedure discards the first four reading in every series and this has virtually eliminated the initial drift of earlier measuring sessions. My results showed and still show inexplicable outliers which have a negative impact on the error profile of the results produced. By mounting the unit on a tripod and making sure it is level and exactly vertical instead of operating it while hand-held, I have reduced the number of outliers but not eliminated them.
The results of the first experiment were obtained at Bergwater Lodge (-33°39’47.06″, 20°00’44.13″, 501m) near Montagu. The objective was to see if the readings taken with the Sky Quality Meter at the zenith (0°) and at 30° and 60° down from 0°, toward each cardinal direction varied and, if they varied, by how much. In experiment 1 the meter was hand-held.
Results for Experiment 1.
Discussion of Experiment 1.
The results in Figures 1 to 6 show that the values given by the Sky Quality Meter do differ at the different cardinal points and also at 30° and 60 ° down from the zenith (0°). At both 30° and 60°, the readings were darker toward the west and east than at 0° and less dark toward the north and south.
In order to illustrate the differences more clearly, the Sky Quality Readings were calculated as a percentage of the value obtained for the zenith (0°) and these results are depicted in Figure 7 (above). Here it is clear that W30°, E30°, W60° & N60° readings were consistently darker than the readings at 0° (average -0.4222) while those for N30°, S30°, N60° & S60° were lighter by a larger margin (average 0.8175).
One set of results is not enough to draw any general conclusions from and I suspect the results will vary from site to site. In all probability, they will also vary from season to season for the same site as the position of objects in the sky changes seasonally. I will select a suitable site and repeat the test at three monthly intervals over the course of one year.
The values in the second experiment were obtained at the SAAO Hostel near Sutherland (-32°22’35.29″, 20°48’18.56″, 1703m). I wanted to verify that my Unihedron Sky Quality Meter’s readings were consistent at 0° when the instrument was rotated 90° between consecutive readings around the vertical axis. In experiment 2 the meter was tripod-mounted and the tripod was set to level and vertical using a spirit level.
Results for Experiment 2.
Discussion of Experiment 2.
From these results, it appears that the Unihedron Sky Quality Meter I use does, in fact, give different readings in the two 90° orientations around the vertical axis that were tested. Even if one takes into consideration the three outlier values the S/N values are consistently darker than the W/E values. It seems possible to produce quite different sets of values, and therefore draw different conclusions depending on how the instrument is orientated around the vertical axis.
I will repeat the test using all four possible 90° orientations around the vertical axis. On that occasion, it will hopefully have the time to take two or three sets of readings on the same evening and also to repeat all of them on two or more consecutive evenings.