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It won't take long to realize that using AA batteries is an expensive way
to feed your NexStar (for those models that offer this option). For a good number of weeks
I used two 6 volt lantern batteries - a NexStar GT will run for days on that power. If you are interested in using this
option, but don't already know how to make the required cables, I would advise against it
as it can be easy to reverse a connection and damage your scope. And in any case
lantern batteries are still too expensive.
So obviously what we really want is a rechargeable power source or an AC
adapter. NiCad and NiMH batteries won't do (unless you make your own
battery holder) as they only produce 1.2 volts as compared to the 1.5 volts
of an alkaline battery. NexStar telescopes require 12 volts to run
correctly, so you would need 10 correctly connected NiCad or NiMH batteries.
Any AC adapter providing 12 volts and at least 1.5 amps should work
fine for the smaller NexStar scopes, though many wall transformers have
suspect power and have been known to cause problems. CGE, CGE Pro, CGEM, GPS and
Advanced Series scopes also require 12 volts, but they require much more
current than is available using small batteries or most AC adapters.
At a minimum, you will need an AC adapter providing 2 full amps for these
models, 3 amps would be recommended. A power supply which provides regulated output voltage
is highly recommended. One good source for a regulated AC to DC power adapter
is www.ScopeStuff.com.
Whatever power source you choose, the correct connector to attach to the
scope has an inside diameter of 2.1mm and an outside diameter of 5.5mm with
positive (+) on the inside conductor. 2.5mm inside diameter is much
more common and provides a loose connection that causes MANY problems in the
operation of the scope. The CGE Pro uses a new threaded power
connector - a nice change as it cannot be disconnected accidentally - but it
is compatible with the old style NexStar power connector if needed.
More info on the power connectors for all these mounts can be found
here.
While AC adapters are in some ways convenient, my recommended power
source for all Celestron computerized telescopes is a rechargeable 12 volt
battery with 7 amphour or greater capacity. The higher the amphour
rating, the longer the battery lasts between charges. You can buy 12
volt rechargeable power sources on most astronomy equipment web sites -
sometimes they are referred to as field power packs. Celestron and
Orion offer small 7 amphour models that will run even the larger scopes for
several hours and larger 17 amphour models that will run a scope for an
all-night session with ease. These power packs also include power
jacks for 3, 6 and 9 volt accessories and have red and white light
flashlights built-in. Both the Celestron and Orion power packs are based on sealed lead-acid
battery technology.
| Other alternatives are 12 volt rechargeable
power sources found in the camping and outdoors sections of many stores
and portable automotive jump-start systems (see the picture to the
right) available at most automotive stores. These are generally
much less expensive than the astronomy-specific power packs but work the
same. These power packs are based on sealed lead-acid battery
technology. With any of these portable battery pack options, the requirements you
are looking for is 12 volts, 7 amphour or greater, a 'cigarette lighter'
socket and a recharger. |
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A few additional notes on rechargeable power sources based on sealed
lead-acid battery technology. To prolong
the life of the battery, recharge after every use. Do
not wait until the telescope starts acting sluggish or the meter on the
battery indicates low power. Also, if the battery sits unused, charge
it at least once a month. You should also be aware that, overcharging
can easily damage and most do not include a recharger with automatic
shutoff. NexStar Group member Phil Chambers provided the following
tip. Plug the charger into a power outlet timer (the little gizmo used to
turn lights off and on to deter burglars while you are away) with all the
'ON' pins removed and only a single 'OFF' pin inserted. Then you can set the
timer to shut-off after the recommended recharge period, generally no more
than 12 to 24 hours. Another option is to purchase a trickle charger from a
marine or automotive parts store. While more expensive, it will keep your
battery in top condition. Be aware though, that some rechargeable power
sources have electronics that prevent a trickle charger from working
properly and that there are a couple of different battery technologies used,
each requiring a different type of recharger. So, you may only learn
by trial and error if a particular trickle charger works for your battery
pack unless you are very familiar with battery technology.
Learn more about rechargeable batteries by reading Jim Towers' guide on
the subject, found here.
Finally, you will need to supply the correct cord to go between most battery packs
and the scope. Astronomy dealers that sell Celestron
equipment can provide the cord or you can try an electronic parts store like
Radio Shack in the US. The cable you are looking for has a cigarette
lighter plug on the end to connect to the battery pack and the plug for the scope end has an inside
diameter of 2.1mm and an outside diameter of 5.5mm with positive (+) on the
inside conductor. Note that the more common connector is 2.5mm inside
diameter. This will not provide a positive connection and leads to
many problems with operation of the scope as momentary power interruptions
cause misbehavior of the electronics of the scope. Again, the CGE Pro
uses a different power connector and includes a power cable with the
required cigarette lighter plug.
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