Electricity

Unless you are using basic equipment, and not doing any photography, some kind of electricity is needed.

Battery

When you buy a new telescope it usually has a 12 volt power cord (or an internal battery pack).  Most new folks hit the dark skies with nothing more than the battery in their car.  As long as you are only powering a scope this is a workable system, however add in a computer, a camera, dew heaters, etc., and you will quickly drain your car battery.  Several companies sell small portable power packs. These will usually run a scope for a night or two, but little else.  

Your best choice is to head down to your local battery retailer (not auto parts store) and buy one or two dedicated batteries to power your equipment.  I have a series 24 that will power the CCD for a couple nights, and a pair of 33 Ah wheelchair batteries that will run scopes several nights.  I highly suggest the sealed Absorbed Glass Mat (AGM) batteries.  Gel cell batteries cost a lot more, require careful charging, can be shock sensitive, and are easy to kill.  Any charger can recharge an AGM, but I find using the gel cycle on my charger prolongs their life.  No matter what battery you end up using, make sure it is deep cycle rated (you will kill an automotive battery with just a few deep discharges) and buy a quality charger.   Recharging them every month or so in storage prevents the shorted plates, freezing, and such, that discharged batteries can suffer.  Recharge them as soon as you get home for the same reason.  Try not to take them below a 50 percent charge level, or you are risking irreversible damage.  I have a couple batteries that are over 10 years old and still going strong.  I have both the old fashioned transformer type charger (heavy) and the new switching electronic charger (lightweight) and they both work well, but they can't work together.  A switching charger creates a lot of line noise and will conflict with any other charger on the same line, then neither charges anything.

You may find running multiple items from one battery to be problematic.  Ground loops can cause weird issues.  I found that I had to have separate batteries for the CCD camera (SBIG ST-8E) and the scope (LX-200), otherwise I got frequent crashes of one or the other.  I could connect the laptop to either source and it worked fine, just something between the camera and scope was the culprit.

Generator

Home center type generators are fairly low priced, but with the lower price comes a major problem - noise.  Most of them make a lot of noise.  You won’t want to sit out all night listening to one, not to mention if there is anyone else around, you may draw incoming fire.  Daytime use to recharge batteries and such is usually OK.  The electric coming off these beasts can be quite noisy, I’ve seen bargain priced generators where some electronic items wouldn’t work properly.

Honda generators are the best thing going.  They are ultra reliable, lightweight (I can move mine around one handed) and they are the quietest of the bunch.  Yes you pay more, OK a lot more, but set one at the end of a 50 foot extension cord and you will hardly notice it running.  The 2000 watt unit will allow you to carry on a normal conversation while standing right next to it.  Some star parties will allow them to run at night.  They use inverter technology, so the electricity is fairly clean and stable, everything I’ve ran on mine works well.

Don't try recharging your expensive batteries off the 12 volt output of a generator, even if it is labeled as a charger.  They are usually unregulated and will ruin a good battery with a couple uses.  Take along your good charger and use it, but try it before hitting the field - chargers that use a switching power supply instead of a transformer won't work with most generators.  Make sure it completely charges the battery before trusting it.

110 volt

Wouldn’t it be great if every tree had a 110 volt outlet?  I prefer to run all of my astro items on 110 volts.  I don’t have 12 volt ground loop issues creating problems, or voltage drop issues, nor do I have to worry about one battery dying earlier than expected.  A long extension cord, a power strip and I’m in business.  Some star parties have community 110 volt available, bring lots of cords and understand the rules for use.  I hear some star parties have problems keeping stable power going, so check ahead and bring batteries for backup if needed.

Inverters are a great way to bring 110 volts into the great outdoors.  Modern inverters are around 95% efficient, so little of your precious battery power is wasted.  Also, make sure you choose an inverter that has a full or modified sine wave.  A half wave inverter may not work with some electronics.   A quality inverter will have an alarm when the battery voltage falls low, and will then shut down if the battery reaches a critical level.  As with the generator, a little extra money spent here will be worth it.  

To maximize your battery run time you want to use the right size inverter.  Too big of inverter will work well, but will waste more battery power than a smaller one.  Obviously if you use too small of inverter it will just shut down when it overloads.  Measure the wattage of all the items you will be using and add them up.  The best way to measure the wattage is to do it as a group.  Put an amp meter in line (amps x 110 = watts) and plug everything in at once .  Set it up for maximum draw, in other words, CCD cooler at 100%, laptop battery dead, dew heaters at max, slewing at max speed, etc.  Slickest way to measure the wattage is to obtain a “Kill-A-Watt” meter, available from many retailers for about $20.  Add about 10% for overhead, colder weather, etc., and buy an inverter that just covers it.  My setup draws about 420 watts, so I use a 500 watt inverter.

My Setup

Home - I just run an extension cord and run everything on 110 volts.

One night out -  If I am going to a dark site for an evening, I take the series 24 battery, the 500 watt inverter and everything is running on 110 volts.  If I am not running a camera, then one of the 33 Ah batteries powers the scope on 12 volts.

Multiple nights out - We take the RV when going for multiple nights.  I have a pair of 6 volt golf cart batteries on it.  They allow us to dry camp for a couple weeks without running a generator if we are not watching a lot of DVDs when it rains.  I can run the full astro setup, off of the 500 watt inverter, for at least two full nights, then I will run the generator and recharge the batteries.

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