The cigarette plug is a convenient way to tap into 12V power, but it is not the best connector for passing large amounts of current. This is not due to quality issues, it is simply a design limitation of cigarette plugs and receptacles because their contacts do not make sufficient metal to metal contact. A good electrical connection has a quality known as "low-resistance" which keeps it from getting hot and reduces voltage losses resulting in higher voltage at your heaters (important for large scopes). So if you find your cigarette plug gets hot after a while then the connection is unable to handle the amount of current flowing through it. In addition, cigarette plugs have standard fuses in their tip and since all standard fuses have resistance this creates a voltage loss.
As a general rule, telescopes under 10" will not have a problem with the Standard Cigarette Plug power cord because the amount of current is 3 amps or less. Scopes 10" to 12" will usually work with the Standard Cigarette Plug power cord but the Heavy Duty Power Cord will insure maximum voltage at the heaters and provide the best dew-fighting performance. Scopes 14" or larger will draw over 5 Amps and really need the Heavy Duty Power Cord. If you absolutely must use a cigarette plug with a large scope then I would suggest ordering the Heavy Duty Power Cord with the Cigarette Plug Pigtail. The heavier gauge wire will help and you can always order another pigtail if you decide to switch to a better power source (to order pigtails alone use the accessories order form).
The Heavy Duty Power Cord (see photo below) allows maximum current flow by keeping resistance as low as possible with larger gauge #16 AWG wire and by using an internal low-resistance solid state PST fuse. The PST fuse never needs replacement, if it triggers it will reset on its own when the over-current condition is removed and the fuse cools off. Another advantage of the PST fuse is that it has extremely low resistance so higher voltage reaches the heaters allowing them to produce more heat at full power.
The Heavy Duty Power Cord is available with the following connectors:
Molex Connector - used in conjunction with a "Pigtail" that adapts the power cord to fit your power source. Many different pigtails are available including ring terminals, RCA plug, banana plugs, and cigarette plug. This allows flexibility to have several pigtails to adapt to multiple power sources. For example, you might use one pigtail at home with a Power Supply to operate on 120 VAC, but then use a cigarette plug pigtail in the field when operating from a battery pack.. Please note that the Cigarette Plug Pigtail is offered for convenience, it has no greater current capability than the Standard Cigarette Plug Power Cord. When ordering a Ring Terminal Pigtail you will need to specify the size of the hole in the terminal. Standard sizes are 1/4", 5/16", and 3/8" and if your positive and negative terminals are different sizes you may specify this in the comments section of the order form. Other sizes are available upon request. If you are using a Pyramid Power Supply the ring terminal size is 1/4" and they will also accept banana plugs.
Banana Plug - a universal connector that will fit the Pyramid Power Supplies as well as most others. It is a good choice if you will only operate from a power supply and never intend to use a battery.
Stripped & Tinned Leads - you can order the Heavy Duty Power cord without a connector if you would like. The end of the cord will have the wires stripped and tinned and polarity marked. You can then connect to your own terminals.
