Can the DewBuster™ Controller handle a 14" SCT?
Yes, the DewBuster™ Controller works well on a 14 and eliminates the need
for a second controller. Efficiency is very important so be sure to
place the
heater strip around the aluminum tube just behind the corrector plate casting
and use a dew shield. The
ring terminal option is strongly recommended to
reduce voltage losses.
Will the cigarette plug power cord work on a 14" SCT?
If your only means of connecting is a cigarette socket then the cigarette
plug will work but it is not ideal. The big 14" heater demands quite a bit of
electrical current which requires very low resistance in all wiring and
connections. DewBuster™ Controllers equipped with
heavy
duty power cords have a solid state PST fuse and heavier gauge wire
for low resistance and efficient current flow. This delivers full voltage to the
heater allowing it to produce maximum heat. For best results I recommend
ordering your controller with the heavy duty power cord and banana plugs,
stripped&tinned leads, ring terminals, or a Molex plug with one of these
connectors. Note that while a cigarette plug pigtail is available for the heavy
duty power cord with Molex plug, the cigarette plug will be the bottleneck as it
is not a low resistance connector. It does however allow you the flexibility of
using a cigarette plug and if you upgrade to a better power source all you need
is the appropriate pigtail. If you order your controller with the standard
cigarette plug power cord you may send your DewBuster™ Controller in at any time
for an upgrade to the heavy duty power cord (cost will be $10 return shipping
plus the cost of the power cord and any pigtails).
How can a DewBuster™ Controller keep my 14" SCT
from dewing up if my old controller couldn't? Can it produce any more heat than
other brands?
Small changes in battery voltage cause large changes in heat output (see
chart below). Most controllers have cigarette plug power cords and standard
glass fuses, both of which cause voltage losses when large amounts of current
are flowing. This prevents your 14" heater from producing the maximum heat it is
capable of. In addition, the resistance in the cigarette plug causes it to get
very warm and this heat is wasted energy. A DewBuster™ Controller equipped with
the
heavy duty power cord has heavier gauge wiring, a solid state PST
fuse, and low resistance connections which will not get hot when large currents
are flowing. This means full battery voltage reaches your heater producing
maximum heat with very little wasted energy. The DewBuster™ Controller's also
conserves battery power by using the temperature control to only apply heat when
needed. This results in energy savings early in the night when the outside air
is cooling down. The energy savings translate to higher battery voltage later in
the night when you need it the most. For maxim performance, be sure to
place the
heater strip properly and use a dew shield. Also consider wrapping
the heater with insulation to reduce heat loss.
How much does battery voltage affect heater wattage?
As shown in the graph below, a fully charged battery will produce
almost twice as much heat as a discharged battery. Note that the heat generated
depends on the actual voltage reaching the heater, not just the battery voltage.
Because a cigarette plug power cord has resistance in both the glass fuse and
the cigarette plug connections, the voltage at the heater will probably be about
one volt less than battery voltage which translates into a 20% reduction in
heat. A
heavy duty power cord has much less resistance
which means the heater voltage is much closer to the battery voltage and your
heater will be able to produce more heat.
Can a second heater strip be added?
The 14" heaters are marginal in heating capacity, so if the DewBuster™
Controller's Temperature Controlled heater LED remains on constantly this tells
you the telescope is not warming up to the desired temperature despite the
heater applying maximum heat. Before adding a second heater, try to reduce
wasted heat by wrapping your heater with insulating material to improve its
efficiency. A DewBuster™ Controller with
ring
terminals can handle the extra current for a second 14" heater
(second sensor is not needed, just plug heater into second RCA output of the
Temperature Controlled output that the first heater is on). Since the DewBuster™
Controller monitors temperature, once temperature is reached it will reduce
power and both heaters will use no more power than than a single heater.
