Unihedron Sky Quality Meter, Error Identification and Elimination

Background

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.

  1. Experiment 1.

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.

  1. Results for Experiment 1.
The readings toward the east (E30°) and West (W30°) were consistently similar and both sets were slightly better (darker) than the zenith readings. The values toward the North (N30°) and south (S30°) were consistently less dark than the East & West readings with the N30° readings slightly better (darker) than the S30° ones. I have no explanation for the outlier in the S30°set.
The readings toward the east (E30°) and West (W30°) were consistently similar and both sets were slightly better (darker) than the zenith readings. The values toward the North (N30°) and south (S30°) were consistently less dark than the East & West readings with the N30° readings slightly better (darker) than the S30° ones. I have no explanation for the outlier in the S30°set.
The E30° readings were darker than either the 0° readings or the W30° ones. The W30° readings were marginally less dark than the 0° values. The values for N30° were quite close to the other values but not quite as dark and S30° was noticeably different and again the lowest (least dark) of the five sets.
The E30° readings were darker than either the 0° readings or the W30° ones. The W30° readings were marginally less dark than the 0° values. The values for N30° were quite close to the other values but not quite as dark and S30° was noticeably different and again the lowest (least dark) of the five sets.
The E60° readings were darker than either the 0° readings or the W60° ones and both sets were darker than the 0° values. The values for N60° and S60° were quite close to the other values but not quite as dark, however, all the different sets were much closer together than in Figures 1 and 2.
The E60° readings were darker than either the 0° readings or the W60° ones and both sets were darker than the 0° values. The values for N60° and S60° were quite close to the other values but not quite as dark, however, all the different sets were much closer together than in Figures 1 and 2.
The E30° readings were darker than either the 0° readings or the W30° ones. The W30° readings and the 0° values are very close to each other. The values for N30° and S30° were also quite close together but, in this case, the N30° values were marginally less dark than the S30° ones.
The E30° readings were darker than either the 0° readings or the W30° ones. The W30° readings and the 0° values are very close to each other. The values for N30° and S30° were also quite close together but, in this case, the N30° values were marginally less dark than the S30° ones.
The W60° readings were now the darkest ones followed by the E60° ones. The 0° readings and the S60° values are hardly distinguishable with the N60° values just slightly lighter.
The W60° readings were now the darkest ones followed by the E60° ones. The 0° readings and the S60° values are hardly distinguishable with the N60° values just slightly lighter.
Depiction of the % difference between zenith (0°) readings and other values.  Zenith values were taken as 100% so negative values indicate series of readings that were higher (darker) than zenith readings.
The depiction of the % difference between Zenith (0°) readings and other values. Zenith values were taken as 100% so negative values indicate series of readings that were higher (darker) than zenith readings.
  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).

  1. Future Planning.

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.

  1. Experiment 2.

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.

  1. Results for Experiment 2.
The two sets of south/north (S/N) -readings are consistently darker than the west/east (W/E) -readings. Despite the three outliers, the two sets of S/N-readings lie quite close together as do the two sets of W/E readings.
The two sets of south/north (S/N) -readings are consistently darker than the west/east (W/E) -readings. Despite the three outliers, the two sets of S/N-readings lie quite close together as do the two sets of W/E readings.
  1. 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.

  1. Future Planning.

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.

Stargazing visit to Leeuwenboschfontein: Monday 26th of December 2016 to Sunday 01st January 2017.

The day after Christmas we (Lynnette, Snorre and I) arrived at Leeuwenboschfontein just before lunch. We were followed later in the week by Iain Finlay – Willem stayed at home keeping their cats, Tiger and Aimé, company. Rob Bark with his wife Michelle and daughter Victoria were next in, followed, eventually, by Paul Kruger, with his famous breakfast. Dave, Spiro and Sharon were due to fly in from up north but eventually drove down due to thundery weather over the central parts of the country.  Martin Lyons had plans to fly in as well but gave up on that idea as the altitude, heat and short runway made it unsafe for the plane he was going to use. Auke could not make it either because of last minute complications.

I have to sit here all morning and wait for them to finish so that we can get going and go to Leeuwenboschfontein.
I have to sit here all morning and wait for them to finish so that we can get going and go to Leeuwenboschfontein.
TOP LEFT: Earth shadow and Venus’s girdle with one of the nice new bungalows at Leeuwenboschfontein in the foreground. BOTTOM LEFT: Iain Finlay, Rob Bark and I on the stoep of bungalow no. 5; one of the spanking new bungalows at Leeuwenboschfontein. TOP RIGHT: Two single beds pushed together to make a double bed in our bungalow. MIDDLE RIGHT: The bunk-bed and washbasin in our bungalow. BOTTOM RIGHT: Two burner gas stove, fridge and table with two benches in our bungalow.
TOP LEFT: Earth shadow and Venus’s girdle with one of the nice new bungalows at Leeuwenboschfontein in the foreground. BOTTOM LEFT: Iain Finlay, Rob Bark and I on the stoep of bungalow no. 5; one of the spanking new bungalows at Leeuwenboschfontein. TOP RIGHT: Two single beds pushed together to make a double bed in our bungalow. MIDDLE RIGHT: The bunk-bed and washbasin in our bungalow. BOTTOM RIGHT: Two burner gas stove, fridge and table with two benches in our bungalow.
Dalzicht on the left, with bungalows one and two hidden behind the island in the road. They are both equipped with their own bathrooms. Bungalows four to six on the right use the ablution block hidden in the background behind unit three.
Dalzicht on the left, with bungalows one and two hidden behind the island in the road. They are both equipped with their own bathrooms. Bungalows three to six, on the right, use the ablution block hidden in the background behind unit three.

Monday evening was fine, Tuesday evening was completely clouded over and Wednesday evening was very windy in the early evening with a fair amount of cloud that cleared after midnight. Thursday night was a repeat of Wednesday and Friday was more of the same. Saturday was a near-perfect night to round off the weekend.

TOP: Sunset on the 30th of December. SECOND FROM THE TOP: Sunset about 20 minutes later. BOTTOM: The Moon going down for the last time in 2016 over Leeuwenboschfontein.
TOP: Sunset on the 30th of December. SECOND FROM THE TOP: Sunset about 20 minutes later. BOTTOM: The Moon going down for the last time in 2016 over Leeuwenboschfontein.

One thing that is a problem at Leeuwenbosch is the lighting along the entrance road and in the garden between the guest houses.  They are all these horrible round white things that distribute light in all directions. Some sort of a cover that prevents light from escaping upward and horizontally, would solve the problem and the use of cooler bulbs would also help. I temporarily solved the problem by taking the bulbs out as soon as it looked as if all the folks in the houses had gone to bed and then replaced them when I was done observing. Johan Roux, however, has shown me where the light switches for these lights are and it is now a case of flicking two switches and seeing conditions around the guest houses and new chalets will improve by at least 200%.

TOP LEFT: Paul taking a break on the way to Leeuwenboschfontein. TOP RIGHT: Paul is a firm believer in a hearty breakfast to start his day. BOTTOM LEFT: Paul’s braai and bottle of wine in preparation for the night’s photography. BOTTOM RIGHT: Paul’s very nice set of star trails taken from Leeuwenboschfontein.
TOP LEFT: Paul taking a break on the way to Leeuwenboschfontein. TOP RIGHT: Paul is a firm believer in a hearty breakfast to start his day. BOTTOM LEFT: Paul’s braai and a bottle of wine in preparation for the night’s photography. BOTTOM RIGHT: Paul’s very nice set of star trails taken from Leeuwenboschfontein.

The camp, however, was a bigger problem this time around. Because it was the holiday season and specifically the New Year’s weekend, the camp was full of revellers who switched on all possible lights including that infernal spotlight on the mast in the middle of the camp. Why get tipsy in the dark, after all? The light spill from this lot even affected the seeing down in the telescope area next to the runway, almost a kilometre away.

At least these light pollution problems will not be a problem during the SSP because we have Johan’s permission to switch everything off for that weekend.

On the subject of light pollution, I recorded a set of dark sky readings for those of the readers who might be interested.

MSAS = Magnitudes per Square Arc Second NELM = Naked Eye Limiting Magnitude
MSAS = Magnitudes per Square Arc Second
NELM = Naked Eye Limiting Magnitude

I also recorded some weather data, using Hans van der Merwe’s clever data logger. Here are some results that might interest amateur astronomers.

Graphic representation of some of the weather data from Hans van der Merwe's data logger.
Graphic representation of some of the weather data from Hans van der Merwe’s data logger.

Leeuwenboschfontein Astronomy Weekend: 11 December 2015.

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.

TOP LEFT: Sunrise at Leeuwenboschfontein looking down the Nougaskloof roughly in the direction of the Anysberg which lies to the right but out of the picture. TOP RIGHT: Sunset, but looking east from Leeuwenboschfontein. BOTTOM LEFT: The same sunset as in the previous photograph but looking west from the camping area. BOTTOM RIGHT: The same sunset reflected in the dam in the campsite at Leeuwenboschfontein.
TOP LEFT: Sunrise at Leeuwenboschfontein looking down the Nougaskloof roughly in the direction of the Anysberg which lies to the right but out of the picture. TOP RIGHT: Sunset, but looking east from Leeuwenboschfontein. BOTTOM LEFT: The same sunset as in the previous photograph but looking west from the camping area. BOTTOM RIGHT: The same sunset reflected in the dam in the campsite at Leeuwenboschfontein.
TOP LEFT: The very neatly and sensibly enclosed permanent caravan sites at Leeuwenboschfontein with the two telescopes under their shiny protective wraps. TOP RIGHT: The handy table with power outlet and light behind the shade cloth screen very nicely extend ones living space from inside the caravan to the space in front and the shade cloth affords on a great deal privacy as well as protection from the prevailing wind. BOTTOM LEFT: The tranquil sunset view across the dam from our caravan. BOTTOM RIGHT: The 12” being prepared for the night’s working session.
TOP LEFT: The very neatly and sensibly enclosed permanent caravan sites at Leeuwenboschfontein with the two telescopes under their shiny protective wraps. TOP RIGHT: The handy table with power outlet and light behind the shade cloth screen very nicely extend ones living space from inside the caravan to the space in front and the shade cloth affords one a great deal privacy as well as protection from the prevailing wind. BOTTOM LEFT: The tranquil sunset view across the dam from our caravan. BOTTOM RIGHT: The 12” being prepared for the night’s working session.

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.

Snorre, with his flashing red light. He seems exceptionally at home in the rocky and bushy terrain at Leeuwenboschfontein and tends to disappear at night. With the light we can find him more easily and we think that it not only affords him some protection against predators, but also warns his potential prey of his approach, much to his disgust.
Snorre, with his flashing red light. He seems exceptionally at home in the rocky and bushy terrain at Leeuwenboschfontein and tends to disappear at night. With the light we can find him more easily and we think that it not only affords him some protection against predators, but also warns his potential prey of his approach, much to his disgust.
TOP LEFT: Auke and Chris in a pensive mood. TOP RIGHT: Lynnette, Rose and Alan. BOTTOM LEFT: Lenelle with her back to the camera, Nellie, Auke, Chris and Miemie. BOTTOM RIGHT: Chris, Lenelle, Miemie just visible, Johan with his back to the camera, Barry, Lynnette, Alan sitting on his haunches with his back to the camera and Rose. On the table is the bottle of sparkling wine to celebrate Alan and Rose’s anniversary.
TOP LEFT: Auke and Chris in a pensive mood. TOP RIGHT: Lynnette, Rose and Alan. BOTTOM LEFT: Lenelle with her back to the camera, Nellie, Auke, Chris and Miemie. BOTTOM RIGHT: Chris, Lenelle, Miemie just visible, Johan with his back to the camera, Barry, Lynnette, Alan sitting on his haunches with his back to the camera and Rose. On the table is the bottle of sparkling wine to celebrate Alan and Rose’s anniversary.
TOP: Nellie, Johan again with his back to the camera, Lenell, Chris, Mienie, Barry, Lynnette, Alan and Rose. BOTTOM: Auke, Nellie with her back to the camera, Chris, Miemie, Barry, Lenelle Susan with her posterior to the camera and Lynnette.
TOP: Nellie, Johan again with his back to the camera, Lenelle, Chris, Miemie, Barry, Lynnette, Alan and Rose. BOTTOM: Auke, Nellie with her back to the camera, Chris, Miemie, Barry, Lenelle Susan with her posterior to the camera and Lynnette.

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.

Supper on the grill on Saturday evening in the boma.
Supper on the grill on Saturday evening in the boma.
LEFT: Auke checking out the weather and contemplating the pile of calendars waiting for him at home. RIGHT: Miemie and Barry.
LEFT: Auke checking out the weather and contemplating the pile of calendars waiting for him at home. RIGHT: Miemie and Barry.

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.

TOP: Crux or the Southern Cross is the smallest of the 88 constellations but other than Orion and Scorpius it is probably one of the most distinctive. Two of the stars in Crux appear to have planets and it also contains the distinctive open cluster known as the Jewel Box (NGC 4755) as well as the extensive dark nebulae known as the Coal Sack. Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 5s – f/1.8, 30 photographs stacked and processed with PhotoScape ® BOTTOM: Star trails in the vicinity of Orion. Legend: M1 to M4 are meteor trails and A is the tremor caused by our illustrious President playing ping-pong with his Finance Ministers. Actually, this is the result of Snorre stretching up against the tripod to play with the flashing green light on the camera. B is the trace of the Orion Nebula (M42/NGC 1976) and C indicates the traces of Orion’s three belt stars (Alnitak, Alnilam & Mintaka) also known as the Three Kings or the Three Sisters. Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 4s – f/1.8, The image was generated from 93 photographs taken at 38 second intervals.& processed with StarStax ®
TOP: Crux or the Southern Cross is the smallest of the 88 constellations but other than Orion and Scorpius it is probably one of the most distinctive. Two of the stars in Crux appear to have planets and it also contains the distinctive open cluster known as the Jewel Box (NGC 4755) as well as the extensive dark nebulae known as the Coal Sack.
Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 5s – f/1.8, 30 photographs stacked and processed with PhotoScape ®
BOTTOM: Star trails in the vicinity of Orion.
Legend: M1 to M4 are meteor trails and A is the tremor caused by our illustrious President playing ping-pong with his Finance Ministers. Actually, this is the result of Snorre stretching up against the tripod to play with the flashing green light on the camera. B is the trace of the Orion Nebula (M42/NGC 1976) and C indicates the traces of Orion’s three belt stars (Alnitak, Alnilam & Mintaka) also known as the Three Kings or the Three Sisters.
Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 4s – f/1.8, The image was generated from 93 photographs taken at 38 second intervals.& processed with StarStax ®
TOP: Orion Nebula (M42/NGC 1976) It is a diffuse nebula situated in Orion’s sword at a distance of about 1340 light years. It is the closest area to the Earth in which there is a large amount of star formation in progress. M42 is about 24 light years wide. BOTTOM: Omega Centauri (? Cen/NGC 5139) The largest globular cluster in the Milky Way. Situated at 15 800 light years from the Earth it has a diameter of about 150 light years it contains an estimated 10 million stars. Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 4s – f/1.8, 20 photographs stacked and processed with PhotoScape ®
TOP: Orion Nebula (M42/NGC 1976) It is a diffuse nebula situated in Orion’s sword at a distance of about 1340 light years. It is the closest area to the Earth in which there is a large amount of star formation in progress. M42 is about 24 light years wide. BOTTOM: Omega Centauri (? Cen/NGC 5139) The largest globular cluster in the Milky Way. Situated at 15 800 light years from the Earth it has a diameter of about 150 light years it contains an estimated 10 million stars.
Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 4s – f/1.8, 20 photographs stacked and processed with PhotoScape ®
Eta Carinae at bottom left is a star grouping that contains two stars with a combined brightness that is several million times that of our Sun, It is situated at about 7 500 light years from the Earth in the constellation Carina. The primary star is expected to explode as a supernova in the not too far distant astronomical future. The Southern Pleiades (IC 2602) is an open cluster in the constellation Carina and contains about 60 stars. This cluster is between 35 and 45 million years old and lies approximately 500 light years away with a diameter of about 15 light years. Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 5s – f/1.8, 15 photographs stacked and processed with PhotoScape ®
Eta Carinae at bottom left is a star grouping that contains two stars with a combined brightness that is several million times that of our Sun, It is situated at about 7 500 light years from the Earth in the constellation Carina. The primary star is expected to explode as a supernova in the not too far distant astronomical future. The Southern Pleiades (IC 2602) is an open cluster in the constellation Carina and contains about 60 stars. This cluster is between 35 and 45 million years old and lies approximately 500 light years away with a diameter of about 15 light years.
Camera: Nikon D5100, Lens: AF-S NIKKOR 50mm f/1,8G, ISO: 1000, Shutter: 5s – f/1.8, 15 photographs stacked and processed with PhotoScape ®

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.

Kopbeenskloof – May 2014

Exploring the Astronomy Potential at Kopbeenskloof

This report is a bit late.  I thought I had written it and obviously I hadn’t so now I have to write it and look as sheepish as possible about the fact that it’s so late.

In May Lynnette and I went of to investigate a place we’d had our eye ever since we’d visited Leeuwenboschfontein a few kilometres further down the road in 2012. Other than the ominous sounding name it has the added attraction of being situated at over 1200 m above sea level and that, makes it one of the highest farms in the Western Cape Province.  For the astronomers who also hike or walk during daytime, there are lots of trails and hikes and the farm is also ecologically interesting as it straddles the transition from typical Renosterveld to the Cape Mountain Fynbos.

The farm is run by Wouter and Elsabé Stemmet and regularly hosts groups of up to 200 from various youth organizations such as the Voortrekkers and Land Care & Land Services. These groups make use of a number of very basic wooden chalets containing only bunk beds. For the chalets there are adequate ablution facilities and a large, well equipped kitchen as well as an outside braai area. Wouter and Elsabé also cater for large functions and large groups, if asked to do so.

View of the one group of chalets
View of the one group of chalets
View of one of the second group of chalets
View of one of the second group of chalets
The very nice outside braai area for the chalets
The very nice outside braai area for the chalets
Part of the interesting inside braai area
Part of the interesting inside braai area

A separate camping area for tents and caravans that has its own ablution facilities is also available.

There is a rustic cottage for four that has no electricity and one heats the shower water by making a fire, situated about 200 m from the main house and the chalets.

The guest house, that could sleep nine in three en-suite bedrooms with double beds and three single beds in open areas, is situated about two km away from the main house and the chalets. The house has a kitchen with a stove, microwave and fridge and also has a large inside fireplace suitable for having a braai, should the weather turn nasty. All bedding and towels are supplied and further details can be found on their website if you go here.  One last thing is that mobile phone reception is limited to one spot in the garden of the main house and I do not know if one can get a signal for all three service providers there.

To get there one takes the R318 from the N1 and, after 26 km you turn left onto the Nougaspoort gravel road. After six km the turnoff to Kopbeenskloof is on your right and then you just follow the road to the main farm house, the chalets and the rustic cottage, or go past the house, keeping to the left and after two gates, you will be at the guest house.

The reason we went there was to try and evaluate Kopbeenskloof for future astronomy outings.  It might work for a Star Party but the chalets are very basic and the area around the chalets does not really lend itself to placing telescopes and I can also see the astrophotography people experiencing problems with power. I  think the chalets and the camping are too far apart to allow the groups to interact easily. I would, however, not rule the site out for Star Parties, as one could possibly overcome some of the perceived difficulties by negotiating with Wouter and Elsabé.

The rustic cottage could work for a small group with Dobbies, or even equipment that will run off batteries, which I am sure the owners would be more than happy to allow one to re-charge the next day.

The outside amenities at the guest house. Fortunately no longer  in use but the pines on the left lie to the south of the house and those in the background are to the west
The outside amenities at the guest house. Fortunately no longer in use but the pines on the left lie to the south of the house and those in the background are to the west
The back of the guest house as seen from the south east.  The pines to the west of the house can be seen in the background
The back of the guest house as seen from the south east. The pines to the west of the house can be seen in the background
This is Leeuwenboschfontein's "Eagles Nest"  to the North west of Kopbeenskloof. Where I intend spending a clear night with a telescope  some time in 2015.  Line of site distance from the guest house to there is about 10 km.
This is Leeuwenboschfontein’s “Eagles Nest” to the north west of Kopbeenskloof, where Lynnette and I intend spending a clear night with a telescope some time in 2015. Line of site distance from the guest house to there is about 10 km.

The guest house is a suitable site for doing astronomy and astrophotography but obviously only for small groups. There are some limitations as the house has tall pine trees on both the western and southern sides. The trees are about 25 m from the house but the area other side the trees is open so one can put a telescope there. The areas north and east of the house are open but the house then creates a high horizon to either the south or the west. The site is dark but unfortunately when we were there the weather was not good and we had partially cloudy weather on the first two nights and complete overcast on the third night. One aspect of the site that needs mentioning is the very noticeable sky glow from Worcester if there is even the slightest hint of cloud along the western horizon.

Sunset was quite spectacular and here one gets a good idea of how low the horizon on that side is
Sunset was quite spectacular and here one gets a good idea of how low the horizon on that side is
More sunset a little later on
More sunset a little later on
A single shot up at Scorpio
A single shot up at Scorpio
The sky glow from Worcester and De Doorns reflected against the low clouds
The sky glow from Worcester and De Doorns reflected against the low clouds at around 21:30
Venus and the moon in the dawn sky
Venus and the Moon in the dawn sky
Moon and Earth shine before dawn
Moon and Earth shine before dawn

Here are my Sky Quality Meter readings taken at the guest house on Kopbeenskloof.

Place: Kopbeenskloof Guesthouse
Locality & GPS: -33°35’53”, 19°57’27”, 1250m

Date: 26/05/2014
Time (SAST): 00:10
Temp (°C): 11.00
Comments: (Z)
Average (10) (MSAS): 21.21
StdDev (MSAS): 0.034705
NELM (V mags): 6.2298

Date: 26/05/2014
Time (SAST): 00:50
Temp (°C): 11.00
Comments: (Z)
Average (10) (MSAS): 21.17
StdDev (MSAS): 0.013333
NELM (V mags): 6.2102

Date: 27/05/2014
Time (SAST): 23:20
Temp (°C): 08.00
Comments: (Z)
Average (10) (MSAS): 21.37
StdDev (MSAS): 0.051034
NELM (V mags): 6.3152

Date: 27/05/2014
Time (SAST): 23:50
Temp (°C): 08.00
Comments: (Z)
Average (10) (MSAS): 21.42
StdDev (MSAS): 0.008498
NELM (V mags): 6.3408

I think one needs to get a group together, stay at the guest house, do some astronomy there and then take a decision on how suitable the site is. A summer visit might be our best bet.

DarkSky Weekend at Bergwater Lodge, Pietersfontein, Montagu

DarkSky Weekend at Bergwater Lodge, Pietersfontein, Montagu:  26th February to 02nd March 2014

26th of February
Lynnette, Snorre the cat and I left home in the Vito on Wednesday the 26th of February hoping to get in at least one extra night’s observing at Bergwater Lodge. On the way there we stopped off at the Pitkos Farm Stall to buy ripe figs and at Pinto’s Butchery in in Paul Kruger Street in Robertson to buy cheese grillers.  In Montagu we stopped off at Marina le Roux the vet’s surgery for Snorre’s annual check-up, which he passed with flying colours and then on to Bergwater.  It was hot when we left home and even hotter when we arrived at Bergwater Lodge.  After unloading and storing everything away we relaxed and waited to see what the weather would do in the evening.  The weather turned out to be superb for stargazing, crystal clear and the upper atmosphere nice and stable.  At 02:00 the average of 20 sky brightness readings, taken with a Sky Quality meter, was 21,6395 magnitudes per square arcsecond (MPSAS) which translates to a naked eye limiting magnitude (NELM) of  6,4544 V mags. By 04:00 we were falling over our own feet so we packed it in and went to bed.

27th of February
On Thursday Jannie and Eddie Nijeboer, who are old hands at Bergwater, arrived during the course of the afternoon and settled in.  Thursday evening started out very nicely and then, shortly after 22:00 the clouds moved in.  By 01:00 it was completely overcast and we decided it was not going to clear so we all went off to bed.

28th of February
Friday dawned bright and clear but day still ended up being very hot.  The rest of the group slowly trickled in. Wendy Cooper (Secretary of the South Peninsula Astronomy Club) arrived in good time followed by a first timer at Bergwater, John Richards (a long standing member of the Cape Centre), Ralph and Sheila Baker (novice stargazers and guests of Jannie and Eddy) also arrived with daylight to spare.  The rest, Martin Coetzee (Orion Observation Group), Lia Labuschagne, (Chair of ASSA’s (Astronomical Society of Southern Africa) Cape Center), Wendy Vermeulen (Cape Center member) and Brett du Preez (astrophotographer of considerable repute –  see the cover of the 2014 SkyGuide), all arrived after dark.

Lia and Wendy, in keeping with the well-established tradition at Bergwater, went sightseeing after dark up to Doringkloof.  We did not know about their intention to recce the area so Martin kindly drove me back to the R318 to try and contact them but without any success.  We returned to Bergwater hoping they were not in trouble and were quite relieved when they arrived shortly afterwards.

Auke Slotegraaf could not make it due to family complications and was missed by all.  Henry Oliver, Jaco Wiese and Raoul Schwenke, were due to arrive on the Saturday as Henry still had teaching commitments in Wellington.

Friday night started out with some instability in the upper air but that improved as the night progressed.  By midnight conditions were really good.  At around 04:00 on Saturday morning I managed, much to Brett’s amusement, to identify the rising Venus as a plane with its landing lights on or, alternatively, as a possible Alien UFO!  At 01:00 the average of 30 sky brightness readings was 21,7023 MPSAS which translates to a NELM of  6,4851 V mags. The serious observers got to bed well after 04:00 so none of them were about much before 11:00 on Saturday.

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Venus when I first spotted it and thought up all the fancifull explanations about what it was and was not
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Venus a short while later after the penny had dropped

1st of March
Saturday was another scorcher but after rising fairly late many of the group members took the opportunity to cool off in the swimming pool.  Brett set up his binoculars with solar filters so that everyone could look at the sunspots during the course of the day.  With Brett’s help I also managed to take a more or less reasonable photograph of the Sun later in the afternoon.

DSC_5910_Bergwater_01Mrt2014_Dagaktiwiteite
Martin and Sheila digging into some watermelon to combat the heat
DSC_5909
Brett, Martin & Eddy taking it easy in the shade

 

DSC_5908
This is not Eddies midday snooze he is looking at the sunspots through Brett’s binoculars equipped with sunfilters

 

DSC_5905
Sundry telescopes and Auke’s impressive banner depicting the Universe in six informative panels
DSC_5904
Where have all the people gone, gone to cooler spots every one ….
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Martin taking up position for a sunspot viewing session while Brett, Eddy, Jannie & Sheila look on. In the background is a glimpse of the magnificent scenery at the Bergwater Lodge
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Martin heading for the shade and Brett at the binoculars. The high level clouds in the background eventually went away
DSC_5917_Bergwater_01Mrt2014_Son
My image of the Sun. Thanks Brett.

By the time it was completely dark Henry, Jaco and Raoul had not turned up and it later materialized that Jaco’s wife Jacoleen, who is pregnant, had been admitted to an ICU for observation. The rest of the night was perfect for viewing.  Brett eventually sorted out the problem with his equipment – a too long connection cable.  As he did not have a shorter cable there, he did the next best thing and switched to binocular observation, as he had done on the previous evening.  At 11:00 the average of 30 sky brightness readings was 21,5970 MPSAS which translates to a NELM of  6,4333 V mags.  Lynnette and I only got to bed well after 04:00.

Telescope activities
An animated GIF depicting some of the action around the telescopes at night

2nd of March
At around 05:00 on Sunday morning the power went off, not only at the Lodge, but in the entire valley.  Apparently ESKOM was carrying out scheduled maintenance but somehow the Lodge had not been notified.  This caused special problems at the Lodge because it put the pumps that supply the Lodge with water out of action which meant that, when the toilets had been used once, the cisterns did not refill.  The power only came back on after 17:00 that afternoon.

The power outage and associated water problem meant that nobody could prepare breakfast so most people left earlier than usual to have breakfast in Montagu or Robertson.  Lynnette and I relaxed for the rest of the day and made our preparations for the guests we expected for the stargazing event on Sunday evening.