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About Islander

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  1. Take the mirror out and look at a light source through the back (non-reflective) side of the mirror. That'll give you a good idea of the condition of the coating - if it appears perforated then you know it's degrading and is going to need a recoat at some point in it's future. I recommend Vacuum Coatings/Scientific Mirrors for this, they're very helpful and will work with you. However, having said that I'd give the surface a clean (with a gentle soap solution - I use a weak solution of Lux flakes for this - a rinse with clean water and a final rinse with distilled water) and carry on using it. It's not that bad at the moment and perfectly usable - you really won't notice a problem at this stage.
  2. Give Scientific Mirrors/Vacuum Coatings a ring. They're very helpful and very high quality. Here's a link to their price list: http://www.scientificmirrors.co.uk/vcsm-Aluminising.html
  3. Both for me, backed up with a decent (Tirion) star atlas
  4. Fair enough but they're still objects that have been ejected from the Earth by an impact, and then returned by gravity albeit on a short time scale. They're a record of a cataclysmic event. Mars and Moon meteorites are also produced by and are records of cataclysmic events. It depends on viewpoint I suppose.
  5. Tektites tend to be more like a glass. They're formed from the ejecta of a large impact with the high energy yield and pressure and temperatures that that implies - normal rock simply won't survive that unchanged. John mentioned Moldavites which have the appearance of a beautiful green patterned glass and are thought to originate from the Nordlinger Ries impact crater in Bavaria. I have some Indochinite tektites which have a black glassy appearance similar to weathered obsidian.
  6. We have tektites, which consist of material ejected from the Earth's surface by impactors and then returned by gravity.
  7. I've used Scientific Mirrors/Vacuum Coatings in the past and found them to provide a quality service and be very helpful indeed. I wouldn't hesitate to use them again. http://www.scientificmirrors.co.uk/vcsm-Aluminising.html They're worth giving a call.
  8. I have a Jack Pyke Tundra hat which is windproof and toasty warm http://www.jackpyke.co.uk/products/clothing/hats-and-gloves/tundra-hat.aspx
  9. I bought one of these today and first impressions are good. It has 4 charge rates, one for 6v batteries, one for motorcycle batteries (<=14Ah), one for car batteries (>14Ah) and one for AGM batteries. It does pulse charging, trickle charging and runs a desulfate cycle too.
  10. Coming up from the south there's a lot of single track - the section from Rhiconich up might be a problem if there has been snowfall. The approach from the east along the north coast might be a better route if there's dodgy weather but check the reports - there's still a lot of single track to deal with. The Orkney Aurora group on Facebook is a very useful resource. It reports the slightest display.
  11. Sango is a lovely campsite and the drive up to it is sublime. You should be able to see any displays from the site, or better still from the beach. I can recommend a visit to Smoo cave (a couple of miles east of the site and clearly signposted) and if you have time and the service is running (I'm not sure what the arrangements are this time of year) then the ferry and minbus to Cape Wrath is also worth a try.
  12. This time of year, there are ferries from Aberdeen to Kirkwall, Scrabster to Stromness, and Gills Bay to St Margaret's hope. Plenty of options Light pollution is fairly light outside of the larger towns (Kirkwall, Stromness etc.) and the local council are replacing sodium lights with LED ones which has improved matters no end at all. There's the Flotta flare but as long as there's no cloud it really isn't that much of a problem. It's easy to find a dark sky and I'd be happy to recommend places if needed.
  13. The further north you go, the better your chances of seeing a weak or average display. Don't go to Thurso though, as the light pollution will wash the skies out. Displays can be visible on the Moray coast or even fiuther south but those are the exceptiional ones. If you want to stay on tne mainland then I'd be heading for somewhere dark like Bettyhill or one of the other towns out that way. If you can manage it, then Orkney is an even better proposition.
  14. I^2 x R and V^2/R are derived from Ohm's law and the standard power equation. Ohm's law says that the voltage across a resistance is a product of the resistance and the current in amps, i.e. V = I x R Power in Watts is the product of the voltage across a load and the current through thatt load, i.e. P = I x V So, if you know the current and the resistance and you want to work out the power then you have V = I x R and P = I x V and since we don't know the voltage across the load we can subsitiute the values for current and resistance from Ohm's law in place of the V in the current formula which gives us P = I x I x R or P = I^2 x R Similarly, if we know the voltage and the resistance, since Ohm's law can solve current as I = V/R we can subsititure this in place of current on the power equation giving us P = V/R x V or P = V ^ 2/R Voltage is the electrical pressure or 'push' that moves current around a circuit. Current is the flow itself. Resistance limits the amount of current that can flow for a given value of pressure or voltage. Increase the resistance and less current is able to flow and similarly reducing the pressure or voltage reduces the current as well. Conversely if you reduce the resistance or increase the pressure or voltage, then more current can flow. The higher the current for a given value of load resistance across a circuit the greater the power dissipated in that load. Increasing the power can be achieved by decreasing the load resistance or increasing the voltage. Decreasing the power can be achieved by increasing the load resistance or decreasing the voltage. If you have problems visualising this then think of it in terms of plumbing. The voltage is the head or height of the water source. The higher it is the greater the pressure available. The current is the rate of flow of water and the resistance is the internal diameter of the pipework. Varying these is directly analagous to varying voltage, current and resistance.
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