CLICK HERE
for the "Big Dob" DewBuster™ Controller order form."Big Dob" DewBuster™ Controller
What is the
BDDB "Big
Dob" DewBuster™ Controller?
The BDDB is a special version of the DewBuster™ Controller tailored to the
needs of the large Dobsonian telescope. It was developed in collaboration with
Markless Astronomics to give the Big Dob owner
the benefits of a dew controller with a built-in power distribution rail for
powering accessories on the upper cage.
Markless Astronomics has developed a
mounting bracket, power cables, and DewGuard
wiring kits to make the installation of the Big-Dob DewBuster™ Controller (BDDB)
a simple plug and play installation. Contact
Charlie Starks
of Markless Astronomics for information and assistance with the mounting bracket
and wiring for installation of the controller on your telescope. The Big-Dob
DewBuster™ Controller may be ordered using the
order form on
this web site and you may
contact me if you have any questions about the controller or options
available on the order form.
The BDDB has 6 Heater Outputs and 4 Power Outlets for 12V accessories. Any heater or power outlet is capable of providing the 10 Amp maximum of the controller. Over-current protection is provided by a self-resetting PST fuse inside the controller (no need to carry spare fuses). To facilitate mounting the controller on the Upper Cage, power input to the controller is through a female RCA jack that your telescope wiring plugs in to. For those who wish to share the controller with a second telescope, an optional RCA to Cigarette Plug Power Cord is available (power cord does not need to be purchased with controller, it may be ordered later using the Accessories Order Form). Since many big Dob's already have an AstroSystems Dew Guard on their secondary mirror, you may not need a Temperature Sensor for your DewBuster™ Controller so the Big Dob model is sold without the sensor to reduce your cost. However the controller is equipped with all circuitry necessary so implementing Temperature Control is as simple as plugging in a Temperature Sensor. The order form has a place to add a Temperature Sensor to your order or you may purchase it at a later date by using the Accessories Order Form. When a Temperature Sensor is not used the associated outputs are not wasted, they switch over and function as Medium Power outputs. The DewBuster™ Controller has a control knob which is normally used to control the differential temperature (degrees F above air temperature) of the Temperature Controlled heaters. However the control knob has a dual function and when set below 10 the Medium Power Heaters operate at 40% duty cycle which is enough heat in most cases. When the control knob is set above 10 the duty cycle of the Medium Power Heaters will start increasing and by the time the control knob reaches 20 the duty cycle of the Medium Power heaters will reach 100%.
.
CLICK HERE
for the "Big Dob" DewBuster™ Controller order form.
"Big Dob"
DewBuster™ Controller
Do you offer any power cords to fit the Big-Dob
DewBuster™ Controller?
I offer a fused Cigarette Plug power cord to fit the RCA Power Input Jack
but I do not offer ring terminals because they do not have a fuse. The fuse is
necessary because the tip of the RCA plug is connected to the battery + and must
be fused in case it comes into contact with a grounded part of the telescope. I
also offer a banana plug power cord which is intended to be used with a power
supply (power supplies are fused internally). You may contact
Charlie Starks
of Markless Astronomics who carries a greater variety of wiring options for
powering the Big-Dob DewBuster™ Controller. Another option is to order the
standard DewBuster™ Controller which has more power cord options available since
it does not use an RCA Jack for power input. If you have an unusual situation
you may contact me
and I can probably build a custom power cord to suit your needs.
I have a Schmidt-Newtonian, should I use the standard
sensor or the special Newtonian sensor?
Schmidt-Newtonian telescopes use heater strips so the standard sensor should
be used. The standard sensor clips onto the heater strip and the heater strip
holds it in place. Follow the
same guidelines as for Schmidt-Cassegrains.
Can the DewBuster™ Controller be used on a Newtonian
telescope?
Newtonian primary mirrors seldom dew up because they are a relatively thick
chunk of glass so they retain heat, but a shroud is very important because it
acts as an extremely long dew shield. Most large Dob's use fans that blow air on
the back of the primary mirror to cool it down to the air temperature. The fans
also serve as dew control, the air blowing on it keeps the night sky from
cooling the mirror below the air temperature which helps keep the primary mirror
from dewing up.
The secondary mirror will often dew up because it is closer to the open end of the tube so the shroud is not an effective dew shield for it. The secondary mirror is also a much thinner glass and mounted in an aluminum housing which robs the mirror's heat and radiates it to the night sky. If the only component you need to heat is the secondary mirror then the AstroSystems Dew Guard is probably the best solution. If you have a stalk mounted secondary mirror or if you need to heat other components, then the DewBuster™ Controller may be used with a Newtonian Temperature Sensor to control a heater attached to the back side of the secondary mirror or stalk. The Newtonian Temperature Sensor may be purchased alone or substituted for the standard sensor when ordering your DewBuster™ Controller. Click Here for more information on the Newtonian Temperature Sensor
The DewBuster™ Controller can also be used without a temperature sensor in Manual Mode (see page 4 of Owners Manual ) to warm the eyepiece, finderscope, Telrad, and other accessories. It will still utilize the Low Battery circuitry to prevent running your battery too low and damaging it.
Where is the best place to mount a DewBuster™
Controller on a Newtonian telescope?
The controller weighs about a pound, so on small Dobs a counterweight may be
required on the mirror end to offset the controller mounted near the eyepiece.
However this can be a plus as it may make the scope less balance-sensitive when
changing eyepieces. On larger Dobs, mounting the controller on the upper cage
reduces the need to run heater cables down the truss tubes and the optional RCA
Power Jacks can power accessories such as the
AstroSystems Dew Guard. A Special "Big Dob"
DewBuster™ Controller is available with options that many large Dob owners may
find useful.
Why does my primary mirror stay dew free all night yet
it dews up in the morning ?
Large Dobs may experience condensation when the morning sun rapidly warms
the air and then moisture condenses onto the primary mirror which is still cold
from the night before. The most efficient way to prevent morning condensation is
by keeping the moist morning air from reaching the cold mirror until the mirror
has warmed up to daytime temperatures. You may have success using the wood cover
over the front and a plastic bag over the back of the mirror box.
