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Outdoors + Mains + Power


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Hi!

First off wanted to give a massive thanks to everyone who gave me advice in my previous thread, where I was considering a 200P Dob. It was extremely useful, even if people had differing views.

As a result, my next set of questions revolve around what would happen if I were to purchase a Go-To scope, namely the Nexstar 8SE and how I would power it.

Currently, my thinking is the following. At home in the garden, where it will be primarily used I would have an RCD adaptor in the mains, into which I would plug a weatherproof mains extension reel out into the garden and it would sit in a weatherproof box. Inside the box I would have the mains AC adaptor power block and have the cable run to the scope. Additionally I would have 240V > 12v adaptor into which I would plug the dew heater.

I was wondering, as a basic setup have I missed anything? I believe this would be safe and initially easy to setup. Granted there will be no ventilation, but I doubt the heat will build up to such an extent over a couple of hours?

For portable power I have read a lot on here, and the underlying message I take away is if possible go down the leisure battery route, now I'm no electrician, but I'm sure a basic 1 X Leisure battery / insulated carry box / 2 X 12v car socket ports (individually fused) wouldn't be beyond me (famous last words?) but it would be a project for those lazy rainy Sunday afternoons.

Many thanks, think I'm getting closer to boxing off the decision :)

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Why not go for a Maplin 7amp PSU, then run low voltage power cable (10m Long) out to where you mount will be, add a couple of USB leads (10m with Active Repeater), then tape them together with self amalgamating tape, done mine this way and it very quick to get the power and usb outside and coupled up.....

http://www.amazon.co.uk/TRIXES-Active-Repeater-Extension-USB2-0/dp/B004S67QR2/ref=sr_1_2?ie=UTF8&qid=1352332347&sr=8-2

http://www.maplin.co.uk/13.8v-regulated-mains-power-units-231

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Sobel - Sounds like a good idea but remember - any mains wires or devices powered by them when out in the open (specially at night with dew forming) is a definite shock hazzard.

Though a bit of a hassle, using 12 volt batteries are completly safe since the low voltage is not high enough to produce a shock hazzard.

And if you go the battery route, know that "gel cell" batteries (kind that can be operated in any position) will be damaged if their voltage falls below 11.0 volts. Regular lead-acid batteries are much more forgiving and can be discharged to about 10 volts with little damage to the cells. "deep cycle" batteries are the best since they are designed to operate down to 10 volts with no harm and are designed for long periods of low current drain (astronomy use) but take a little longer to fully charge and be charged in a well ventilated area since hydrogen (explosive) fumes are vented during the recharge.

Lots to consider about safety, costs, etc.

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Hi!

Currently, my thinking is the following. At home in the garden, where it will be primarily used I would have an RCD adaptor in the mains, into which I would plug a weatherproof mains extension reel out into the garden and it would sit in a weatherproof box. Inside the box I would have the mains AC adaptor power block and have the cable run to the scope. Additionally I would have 240V > 12v adaptor into which I would plug the dew heater.

For portable power I have read a lot on here, and the underlying message I take away is if possible go down the leisure battery route, now I'm no electrician, but I'm sure a basic 1 X Leisure battery / insulated carry box / 2 X 12v car socket ports (individually fused) wouldn't be beyond me (famous last words?) but it would be a project for those lazy rainy Sunday afternoons.

First of all the mains supply arrangement sounds fine to me. Simple and effective using standard plug/screw together items.

Any lead acid (gel or spill) has care and lifetime issues.

Further, running long wires has voltage drop issues on 12V, unless running thick wires.

Then you are into making up your own connections, leads etc. Easy to make unreliably if you don't have the skills.

Also easy to generate smoke and flames if you get things wrong. But you won't get an electric shock.

But you can't usually run an extension cable miles to a dark site!

Perhaps miy response is not the expected one as many shy away from mains outside.

The waterproof housing you propose will provide the first line of defence, backed up by the RCD.

Hope this helps, David.

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If you are considering the 8SE, this has a rating of 750 mA power consumption, a 7Ah SLA battery will give you enough for a full nights observing. This can be housed in an old s/h alloy record box or make-up case, which you can purchase at a boot sale, or you can make your own carry container, all that is necessary then is to fix a 12V cigar type socket into the box. All the plugs are fused in the plug tip and you will need to change this to suit the power rating of the scope, to say in the order of a quick blow 1.5 Amp. SLA batteries vary, but the Power-Sonic range or Yaseu types are of good quality, the Power-Sonic have a very long shelf life, meaning that they do not need recharging at regular intervals and will hold their charge for many months ( see manufacturers spec ) At the moment these can be had for in the region of £12 + postage, but you will also need a dedicated SLA charger, these do vary in price, but the rule is you need to charge at at least a quarter of the Ah rating no matter what model you buy. If you want to consider the Leisure battery these are lead Acid and start at about 85 Ah and will run any scope and accessories for very long periods, but the drawback is they are very heavy and not easy to transport or handle, also quite expensive, in addition the purchase of a good electronic charger is advisable, that will trickle charge when charging has been completed. If you want to run mains there is no problem with what you have suggested, except you will have cables running on the ground. A small portable unit will sit under your scope and cables for the most part will be out of the way and transportation to a dark site is no problem. If at some time in the future you change your set up and need more power, then just change your 7Ah for a 17Ah, you will probably find it will fit into your existing container :)

John.

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I had a 240 V external double socket with RCD fitted to the outside wall of my garage. I bought electric cable to make and extension lead and aksed for cable suitable for an outdoor extension lead. I bought the a DRi Box and inside the DRiBox, I have another 6 gang extension lead, again with RCD and surge protector. Inside the DRi Box, I have the power leads for 2 laptop computers, the power lead for the SynSCan GoTo mount and the power lead for as USB powered hub. I have used this set up on about 4 occasions, due to the heavy cloud cover and seems to be safe and satisfactory for me.

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Hi Sobel,

If you are going to work on a 12V leisure battery please be very careful! It may only be 12 volts but they can deliver almost unlimited amps! I have heard tell of a mechanic welding a spanner to the car body (and badly burning his hand) because he was taking the +ve connection off first and touched the car body so completing the circuit. The spanner apparently glowed red hot!

Just because these things are 'low' voltage doesn't mean they aren't dangerous if you aren't sure what you are doing.

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as said 12volts is still dangerous can you imagine around 100 amps going to earth it does create some heat. at least with a rcd you will only get .34milliamps to earth before it trips so in affect its safer than 12v dc. i only use 12v for my scope home or away

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As always, you guys are an ocean of knowledge.

I'll bear it in mind re: the batteries/safety. For the moment, I'll probably buy a generic Maplin based based battery and go from there if I need portability. One thing I have read a lot of is that many people refuse to run their scopes off the mains adapters as they are concerned about surges blowing the electrics.

I hadn't thought about this aspect of it before and am now thinking I should ditch the mains altogether if I get a powered scope and go with a power tank (off the shelf).

Anyone here had problems with power surges blowing their scopes electrics?

Cheers!

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No problems using 240V and extension leads like this provided it's all kept dry. If using a plug in RCD I would suggest testing it and keep an eye on the leads for wear & tear. You shouldn't have any issues with heat build up drawing as these are all very low current devices.

I would however be a little gentle with the mains adaptors as these are generally pretty cheaply made and might not like rapid change in temperature or being physically shocked (kicked/tripped over). Not expensive items, but generally a pain to source the right rating/connectors if they do pop.

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A little 12V sealed lead acid type battery is perfectly safe. I have a couple which I rotate each time I go out. I've even got some small bags which are specially designed to hold the batteries and have a pouch on the side in which sits a female 12V car lighter socket. I just plug in the scope and I am set. Ampage isn't a problem, as long as you don't pull too much at a time (too many things pulling power at the same time), then the scope won't work. Buy a nice intelligent battery charger which you can set to motorcycle, keep the batteries topped up to full to deter gas build up and you'll be fine. I even connected a male lighter adapter to the end of my charger so I can plug it straight into the battery.

Alternatively Celestron and other sell a ready made Power Tank which is basically what I've described in a fancy package. With a built in charger and has red lights on it.

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I should add that the batteries I use are small enough to sit on the accessory tray of my mount.... Extra weight = extra stability on my lowly EQ3. ;)

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On 'power surges' blowing scopes.

Not in the UK. We have good mains supplies here.

BUT. There are lots of power supplies on sale as '12V' that actually give up to 19V off load, and have ripple.

A recipe for a blown scope control.

Quite why so few people with expensive astro kit are prepared to spend a tenner on a decent multimeter is beyond me.

Two minutes checking a power supply before first use saves a lot of money later.

A similar argument goes for chargers that wreck gel batteries.

A repeat of the warning about gel battereis and short circuit current. Even small batteries (5-10Ah) have short circuit currents of 100 to 200 amps. This is arc welder type of current, car starter motor current, etc. Wire insulation will burn. So will hands that try to remove the wires. A ring on a finger, or a metal watch strap will heat to injury temperature.

Any gel battery requires precautions for safety. Just because 12V won't electrocute you, doesn't mean it can't bite in another way.

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