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Science
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- Written by Carol Botha
- Category: Science
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In Betty's Bay we talk about light pollution a lot. Not surprising, as here we have something so precious that it needs protection. Over the years I have noticed a decline in the quality of our night sky. Most of the light pollution is in the form of skyglow from neighbouring towns. For the first time I can now measure the amount of intruding light. It has made more sense to me to purchase a Unihedron Sky Quality Meter than a string of pearls.
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- Written by Dawikeho
- Category: Science
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From the Wits University planetarium newsletter — September Eclipses
There is a partial eclipse of the sun on 13 September from 6:40am to 11:05am (depending where you are), with the maximum at 8:54am. The table below gives the percentage that the moon will obstruct the sun.
UPDATE: Here's a photograph by the author of the 13th September partial, taken through welding goggles.
PLEASE make use of proper eye protection. Eclipse glasses are available from the Planetarium at R6 each, excluding shipping.
| Town | Obstruction |
| Bloemfontein | 20.7% |
| Cape Town | 30.4% |
| Durban | 21.1% |
| East London | 27.5% |
| Johannesburg | 15.2% |
| Nelspruit | 13.5% |
Data obtained from HMNAO [http://astro.ukho.gov.uk/eclipse/0322015/]
On 28 September there will be a total eclipse of the moon. The eclipse starts from 2:09am – 7:23am and will be visible in South Africa, but the eclipse will end for us as the moon sets before the end of the eclipse.
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- Written by Carol Botha
- Category: Science
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Once in a blue moon we might win a lottery or see a leopard in the mountain but for most this will be an extremely rare event. Where did the expression once in a blue moon originate? The modern interpretation of a Blue Moon, which is the second full moon in a month, feels less rare, taking that time flies by so quickly.
Blue Moons occur every two to three years. There can even be two Blue Moons in one calendar year. In 1999 there were two full moons in January and March with no full moon in February. The next double Blue Moon events will occur in January and March, 2018.
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- Written by Prof Michael Orren
- Category: Science
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Bugs, smelly water and marine dead zones-that is no fish zones.
Many, very many, global measurements by oceanographers tell us that the sea almost everywhere from surface to seafloor contains moderate quantities of dissolved oxygen gas. Nonetheless, certain restricted areas either contain far less dissolved oxygen than normal or none at all. Regions with low dissolved oxygen are called hypoxic; those with no measurable dissolved oxygen are anoxic, or anaerobic. Such environments, usually with a sluggish water circulation, are created by an excessive inflow of easily oxidised matter, most usually dead phytoplankton (‘plant’ plankton), which uses up much dissolved oxygen as, sinking, it is decomposed by rapid, efficient bacterial action, in the process recycling the essential major nutrients, carbon, nitrogen and phosphorous.
