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.

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.

Autumn Southern Star Party from April 25th to April 28th 2014

Night Sky Caravan Park, Oudekraal, Bonnievale (-33.012486, 19.994881& 207m)

To start with, a special word of thanks to the sponsors, speakers, newcomers, day visitors and of course the regulars who helped to make the event possible. If you want to read some feedback from people who attended the Star Party please go here.

Sponsors:
Andrie van der Linde, Eridanus Optics,
http://www.eridanusoptics.com/store

Anneliese Carstens, Bonnievale Verhurings, Gelukshoop,
marankis@lando.co.za

Gesina de Wet, Oudekraal, Bonnievale,
nightsky@breede.co.za

SAASTA, South African Agency for Science and Technology Advancement,
http://www.saasta.ac.za

Waltons – Stellenbosch,
http://www.waltons.co.za

Donors
Alan & Rose Cassells – the two lights for the interior of the marquee.

Speakers (in order of appearance)
Martin Lyons – “Live Video Astronomy Demo”
Kos Coroniaos – “Amateur Astronomy in South Africa”
Martin Lyons – “Basic Spectroscopic Astronomy”
Lia Labuschagne – “Brown Dwarfs”
Alan Cassels – “Comfortable observing – Moving the Beast”
Auke Slotegraaf – “Photometry with a DSLR Camera”
Kechil Kirkham – “The SKA – The story so far”
Kerry Patterson – “Planetary Models of Hu Aquarii”
Brett du Preez – “Collimating a Newtonian Reflector Telescope”

Newcomers
Dwayne Engelbrecht, Lia Labuschagne, Charmaine Pretorius, Anneke Steyn, Bernie, Michelle & Keagan Swanepoel, Gerhard Vermeulen and Wendy Vermeulen

Day visitors
Anneliese & Tertius Carstens, Willie Lombard & Elise, Inus & Elsophie van Staden

The “old hands”
Alan & Rose Cassells, Charl and Yolandi Cater, Kos Coronaios, Brett du Preez, Wim Filmalter, Iain Finlay, Kechil Kirkham, Martin Lyons, Kerry Paterson, John Richards, Leslie Rose, Auke Slotegraaf, Willem van Zyl, and of course Lynnette and myself.

The 2014 Autumn Southern Star Parties Group Photo
The 2014 Autumn Southern Star Parties Group Photo

Lynnette, Snorre the cat and I got off to a very early start in Brackenfell and arrived at Night Sky by about 09:30 on Thursday.  Alan and Rose were already settled in and shortly after 10:00 Anneliese Carstens of Bonnievale Verhuurings and her two assistants were on site to pitch the marquee tent.  The whole process took just over 70 minute.  As soon as that was done,  we started putting up the banners and posters and doing all the other essentials to get the inside organized.  Alan and Rose pitched in to help with this and without their very able assistance, the job would have taken a great deal longer.  Thanks guys, as usual your convivial company made an otherwise boring task seem quite fun. Lynnette got the Admin table sorted out, as well as the chairs in the main tent and the coffee bar at the back of the tent.

The banner displayed at the entrance to Night Sky Caravan Park dates back to a 2004 astronomy outreach programme
The banner we displayed at the entrance to Night Sky Caravan Park dates back to a 2004 astronomy outreach programme
The side of the marquee tent facing the main camp area
The side of the marquee tent facing the main camp area
The left side of the tent's interior with the Admin Table on the left.
The left side of the tent’s interior with the Admin Table on the left.
The right side of the tent's interior.  The Sale Table is hidden by the chairs on the right.  All banners, inside and outside the tent, were designed by Auke.
The right side of the tent’s interior. The Sale Table is hidden by the chairs on the right. All banners, inside and outside the tent, were designed by Auke.
The Coffee Table was open all day and all night
The Coffee Table was open all day and all night
The Sale Table later sported binoculars and eyepieces put up for sale by various attendees.
The Sale Table later sported binoculars and eyepieces put up for sale by various attendees.

 

Lynnette at the Admin Table
Lynnette at the Admin Table

Thursday evening didn’t offer much by way of stargazing as it was one of those evenings where the clouds opened up and, just as one thought it was telescope time, they closed in again. Somewhere between 02:00 and 03:00 I got up to have a peek and it was totally clear, but I was too lazy to take the telescopes outside.

During the course of Friday most of the others trickled in, but by sunset there were still people on the list who had not turned up so we decided to move the Pub Quiz forward to the Saturday.

The weather looked indecisive about being cloudy or not, so we socialized and had an uncharacteristically late braai while Martin Lyons started setting up for his live video astronomy demonstration. Unfortunately the electronic gremlins were out in force and even with the able assistance of Kos Coraniaos the system obstinately refused to perform to expectations. As the clouds had cleared up we all dispersed to the telescopes and spent the rest of the evening observing or introducing the newcomers to the wonders of the night sky.

John, Alan & Leslie around the braai fires
John, Alan & Leslie around the braai fires
Paul, Alan, part of the camp and the marquee looking almost due South
Paul, Alan, part of the camp and the marquee looking almost due south
Evening reflection looking south-east
Evening reflection looking south-east
Alan point out a UFO to Paul, or maybe an early star?
Alan pointing out a UFO to Paul, or maybe an early star?

On Saturday Kos kicked off the programme followed by Lia in Martin’s vacant slot. The planned braai turned into a bit of a fiasco, because it started raining quite heavily just as the fires got going nicely. Kos and Wim’s attempts to rescue one of the fires by putting the braai drum on Brett and Leslie’s stoep, had unexpected consequences. Despite the fact that they closed the doors and windows the smoke from the fire still got into the house and tainted everything with a distinct “wood smoke” odour.

I am going to get myself a camera with a CCD this wide
I am going to get myself a camera with a CCD this wide
Leslie, Brett & Wenday at Kos's talk
Leslie, Brett, Wendy, Charmain & Gerhard at Kos’s talk
Lia concentrating on Brown Dwarfs
Lia concentrating on Brown Dwarfs
Reflections on the dam of the rain that was to follow shortly afterwards
Reflections on the dam of the rain that was to follow shortly afterwards

Even though Martin’s talk had been cancelled as a result of his equipment failure, leaving an open slot for an extended lunch, the braai was so late that Alan had to wait for people to finish eating before he could start his talk.  After Alan’s talk, Auke presented Alan with his long-awaited observing certificate and a special t-shirt commemorating his acquisition of a 12-inch telescope.  After that ceremony we took the group photo and set ourselves up for the Pub Quiz after supper.

Alan maneuvering The Beast into position
Alan maneuvering The Beast into position
Alan's ingenious drawing table
Alan’s ingenious drawing table
Auke handing over Alan's observing certificate
Auke handing over Alan’s observing certificate
Alan and the long overdue observing certificate
Alan and the long overdue observing certificate
Alan receiving his 12-inch t-shirt
Alan receiving his 12-inch t-shirt
Leslie & Auke enjoying the sunshine after the rain while the braai fires got going again
Leslie & Auke enjoying the sunshine after the rain while the braai fires got going again
Gesina after delivering the SSP-cake
Gesina, after delivering the Southern Star Party cake
Auke and Gesina in a congenial mood
Auke and Gesina in a congenial mood

The Pub Quiz was contended between six teams. After the first three rounds, three teams were eliminated leaving three to contest the next four rounds before Lia and John’s team made it through to the finals. It was a tight race between these two teams until John’s team took the lead. By that time the weather had cleared completely leaving everyone itching to get to the telescopes, so this year’s Quiz, like the Spring SSP in 2013, was not taken to the individual level. Probably a good thing because John has already won the Quiz twice before on an individual basis!

A rainbow at night is a shepherd's delight or something to that effect
A rainbow at night is a shepherd’s delight or something to that effect
With the clouds looking as if they were clearing people hastily started setting up so that they could start observing after the Pub Quiz
With the clouds looking as if they were clearing people hastily started setting up so that they could start observing after the Pub Quiz
Richard, Charl and Yolandi have spotted something interesting in the evening sky
Richard, Charl and Yolandi have spotted something interesting in the evening sky
Wim is also looking but Yolandi seems to be be worrying about the photographer
Wim is also looking but Yolandi seems to be be worrying about the photographer
Al set up and ready to fire off the first salvo in the Autumn 2014 Pub Quiz
All set up and ready to fire off the first salvo in the Autumn 2014 Southern Star Pub Quiz
The final rounds and on my left gaining steadily, John's team
The final rounds and on my left gaining steadily, John’s team
The final rounds and on my right, putting up a brave fight to stay in the lead, Lia's team team
The final rounds and on my right, putting up a brave fight to stay in the lead, Lia’s team
The winners of the Autumn 2014 Southern Star Pub Quiz. Bernie Swanepoel, Muchelle Swanepoel, Iain Finlay, John Richards and Keagan Swanepole.  Keagan is wearing the coveted Southern Star Party Pub Quiz Floating Rosette
The winners of the Autumn 2014 Southern Star Pub Quiz. Bernie Swanepoel, Michelle Swanepoel, Iain Finlay, John Richards and Keagan Swanepoel. Keagan is wearing the coveted Southern Star Party Pub Quiz Floating Rosette

For the evening and late-night coffee we had a very nice cake baked by Gesina to commemorate the seventh Southern Star Party.  The cake was iced in blue and decorated with silver stars.  The cake also served to celebrate John Richard’s 70th birthday and we wish him well on his next 100 years.  A very nice gesture indeed, thanks Lynnette.

The Southern Star Parties Cake commemorating seven Star parties (and John's birthday)
The Southern Star Parties Cake commemorating seven Southern Star Parties (and John’s birthday this time too)

Sunday’s day-programme went off without a hitch. Auke had to leave just after his talk to get Kos back to Somerset West and then he unfortunately encountered a problem and was unable to return as planned. By evening the sky was clouded over, much to everyone’s disappointment, so we also cancelled the scheduled “Ethno-What’s up Tonight”. Anneliese and Tertius had come over specially for the stars, so it was a great disappointment for them.  However, just as we were sitting down having coffee with them, Leslie knocked on the door and announced that the clouds were clearing so we could set up a telescope and take them on a tour. Before midnight Lynnette and I gave up the unequal battle with the dew and went to bed.

Auke seated, left back talking about photometry with a DSLR camera
Auke seated, left back talking about photometry with a DSLR camera
Kechil talking about the SKA after having shown us how to dance the SKA!
Kechil talking about the SKA after having shown us how to dance the SKA!
Kerry explaining the intricacies of HU Aquarii
Kerry explaining the intricacies of HU Aquarii
Brett explaining exactly why most of us avoid collimating our telescopes
Brett explaining exactly why most of us avoid collimating our telescopes
The sunset was absolutely magnificent
The sunset was absolutely magnificent
Much later we could actually do some stargazing on an absolutely windless night as evidenced by the reflections in the dam
Much later we could actually do some stargazing on an absolutely windless night as evidenced by the reflections in the dam
Over on the far side of the dam a moving red light is reflected in the water
Over on the far side of the dam a moving red light is reflected in the water
The Magellanic Clouds, 47 Tuc, the Tarantula very faintly and a tiny corner of the Milky Way
The Magellanic Clouds, 47 Tuc, the Tarantula very faintly and a tiny corner of the Milky Way

On Monday morning everyone was packing up and saying goodbyes. In-between all the farewells, we took down the posters and banners in the tent, folded up tables, stacked chairs and loaded the trailer. By that evening it was only Lynnette, Snorre, myself and Iain and Willem left.

On Tuesday morning with the clouds building up, Anneliese and her crew arrived to take down the marquee.  Iain and Willem were also packing up and when Anneliese and her crew had finished one of her crew remarked, “Look at those two still struggling with that little tent and we’ve already finished with the big one.”  Iain and Willem did eventually finish and left shortly after midday.  Lynnette and Snorre and I stayed till Wednesday before we left for home via the Pitkos Farm Stall.  Regrettably they had no more roosterkoek by the time we got there so we just had coffee and bought a box of Nuy Muscadel for the next SSP in October 2014 before heading home!

This table gives the sky brightness readings obtained during the Autumn 2014 Southern Star Party.

Place Night Sky Caravan Park Night Sky Caravan Park Night Sky Caravan Park Night Sky Caravan Park Night Sky Caravan Park Night Sky Caravan Park
Locality & GPS -33°00’44.95″, 19°59’41.57″, 207m -33°00’44.95″, 19°59’41.57″, 207m -33°00’44.95″, 19°59’41.57″, 207m -33°00’44.95″, 19°59’41.57″, 207m -33°00’44.95″, 19°59’41.57″, 207m -33°00’44.95″, 19°59’41.57″, 207m
Date 24/03/2014 25/03/2014 26/03/2014 27/03/2014 28/03/2014 29/03/2014
Time (SAST) 22:30 23:30 22:00 22:00 22:00 22:00
Temp (°C) 18.00 17.00 16.00 16.00 16.00 17.00
SQM1 21.68 21.58 21.61 21.67 21.59 21.65
SQM2 21.65 21.57 21.62 21.67 21.60 21.64
SQM3 21.66 21.56 21.62 21.66 21.61 21.65
SQM4 21.64 21.59 21.63 21.66 21.60 21.64
SQM5 21.65 21.58 21.60 21.67 21.61 21.64
SQM6 21.63 21.56 21.61 21.68 21.60 21.64
SQM7 21.65 21.58 21.61 21.67 21.59 21.61
SQM8 21.66 21.56 21.62 21.67 21.59 21.64
SQM9 21.65 21.55 21.61 21.66 21.60 21.63
SQM10 21.66 21.58 21.61 21.66 21.60 21.65
Average (MSAS) 21.65 21.57 21.61 21.67 21.60 21.64
StdDev (MSAS) 0.012689 0.012207 0.008000 0.006403 0.007000 0.011358
Med.(MSAS) 21.65 21.58 21.61 21.67 21.60 21.64
NELM (V mags) 6.4610 6.4203 6.4418 6.4679 6.4343 6.4541

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.

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

 

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

 

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Sundry telescopes and Auke’s impressive banner depicting the Universe in six informative panels
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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
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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.