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  #21  
Old 30-09-2007, 05:11 PM
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[1ponders] (Paul)
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It gets set up in the same place everytime. I've only been using the adapter for the past 3 or 4 months but I've never noticed this before. Next time I'm out I'll go through a process of connecting and disconnecting things and see if it happens again
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  #22  
Old 30-09-2007, 07:26 PM
Karls48 (Karl)
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This is one of the disadvantages of switch mode power supplies. They all have common mode AC voltage noise on their output. On some cheep ones it can be as high as 80VAC. As it is common to both outputs, you cannot measure it by placing multimeter on your positive and negative outputs. You can measure it by switching digital multimeter to AC volts and measuring voltage on one of the DC outputs against AC Earth. The current is less then 1uA therefore it doesnít present any danger of electrocution. In fact if try to measure this voltage with old style analogue multimeter, you wouldnít not get any reading on it because it got input impedance of around 10K Ohms against digital multimeters 10M Ohms.
I have received so many electrical shocks in my life that Iím kind of immune to little tingle but I know that many people are quite sensitive to it.
Linear power supplies donít have this problem but are bulkier, heavier, get quite hot and are more expensive.
Also, when you attach the camera (the one with metal body) to your telescope it is in electrical contact (with most of telescope types) with the telescope, mount and tripod. But most of tripods have plastic or rubber inserts on their feet and therefore whole apparatus is insulated from the earth. This is another possibility for charge to build up on it and to discharge thru your body to the ground.
And check all your mains power points and your extension leads for incorrect wiring. So you donít have the Active and the Neutral wires crossed and check continuity of the Earth
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  #23  
Old 30-09-2007, 07:58 PM
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[1ponders] (Paul)
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Thanks Karl.

A bit of background. The AC adapter for the camera is the canon one for my camera. As far as I know my camera has a plastic body, which is one of the reasons I've been scratching my head over this. My G11 has metal feet in direct contact with the concrete. I take my leads and powerpacks into work yearly and get them checked, plus I have an earth leakage detector on the switchboard of the house. Also I am generally barefooted when outside imaging.

I did get a surprise one night wearing my cold weather gear (nylon) while wearing ugh boots and sitting on a sheepskin cover when the humidity was around 15% and the wind howling from the SW. I got up to focus my ED80 which had my ATiK 16IC attached and I got belted as I touched the focuser knob. As well as me getting belted the ATiK crashed as did the ToUcam 900 on my guide scope. Not happy Jan!! So I had a quick lesson on the facts of insulation and grounding. Fortunately both survived but that pesky little white diode in the 900 is only around 1/10 as bright now
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  #24  
Old 30-09-2007, 08:08 PM
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RB (Andrew)
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I suppose you could always change over to a Takahashi mount with wooden tripod Paul.
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  #25  
Old 30-09-2007, 08:18 PM
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Look on the bright side. At least your nose will be warm in winter.
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  #26  
Old 30-09-2007, 08:45 PM
Karls48 (Karl)
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Well Paul, it was clearly static. Sheepskin, Nylon and low humidity is a giveaway. Next time touch tripod leg first, you will still get belted, but you will not damage your gear. You may actually see small blue spark jumping from your finger. Or avoid sheepskin and nylon combination.
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  #27  
Old 30-09-2007, 08:59 PM
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[1ponders] (Paul)
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I definately make sure I ground myself now when wearing that gear, and yes there was definately a spark and it wasn't a small one. I even heard it crack.
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