Section Contents:
| System Introduction | Heater Tapes | Controllers | Power Units | Battery Packs | Complete Small Anti-dewing Systems | Connection Accessories | Anti-Dewing Heater for Telrad | Main Components Price List | Heater Tapes & Pads Price List | Notes on Heater Tape Sizes | Notes of Power Ratings | Dew Blaster Gun

Wheel-Easy Telescope Moving Dolly
Mini Heater Controller
A low power, low cost controller for dew protecting the smaller telescope

If the lens cell of your telescope is under 140mm (5.5") the "Mini" may be all the heater controller you need. Although the Mini will only handle 1.2amp maximum continuous load, this is more than enough to power, say a primary heater tape AC353 (see table below for spec) and also the AC350 eyepiece heater. Alternatively it could also power the AC351 2" eyepiece tape as the ampere ratings are based on maximum continuous loading ­ if the controller is used at less than full power, which it normally is, some flexibility in amp matching can be allowed. The Mini Heater Controller runs from a 12 to13.8V power supply, has a single six step power output setting and can be split to drive two heater tapes with the addition of an AC297 splitter jack. The Mini has a 1.8m (71") output lead and has an integral cigar lighter plug for power input. With red LED "on" indication. Includes full instructions.

Requires 12 to 13.8V power supply and heater tape to function, not included in the price.

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power
Heavy Duty AC Mains to 13.8V Power Supply
An observatory-quality 6amp (max) regulated power supply
with cigar lighter output for anti-dewing equipment

The perfect power supply for observatory-based anti-dewing systems. Regulated 13.8V 6amp(max) output via "banana" plug and spade terminals as well as cigar lighter socket. In steel desktop case with green LED indicator and power switch. Only available in 220/240V for UK usage currently.

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battery
Heavy-Duty Field Power Station 12V 17.5Ah Battery
A high-power battery system for night long dew protection

The HD Field Power Station has a cigar lighter socket and meter to indicate battery charge and output level. This unit has power to spare and will run an LX200 all night long with a complement of anti-dew heaters running at the same time. Includes integral red night-vision utility light. Even includes built-in jump leads to start your car with its 400amp cold cranking power! High-impact slimline case with carrying handle. Complete with in-car recharging cable and AC mains recharging transformer (220-240V for UK use only available at this time).

Includes a 1.2m long LX and ETX telescope connection cable.

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webcam
4Ah 12V Portable Astro Power Station
A battery power system for the smaller Anti-Dewing rig

The Astro Power Station is a useful power supply for the smaller Anti-Dewing System based around the "Mini" controller above (See below also). With a two-heater setup running at a typical half power, depending on air conditions, it is capable of protecting the smaller telescope from dewing virtually the whole night long (8 hours). The Portable Astro Power Station is packed with features: 1. Twin 12V 12amp cigar lighter sockets - 2. A built in red night light - 3. Three additional output terminals offering 3V, 6V and 9V - 4. A standard Meade type ETX connecting cable with right angle plug (2.5mm jack) - 5. LED battery condition and charge indicators - 6. All power outputs controlled from single switch - 7. In-car recharging cable - 8. AC mains recharging transformer (220-240V for UK use only available at this time)

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smaller
Complete Anti-Dewing Heating System for smaller Telescopes

Based around the "Mini Controller" (AC377), this complete temperature-controllable anti-dewing system is the best way to keep dew away from your 5" (tube) diameter or less telescope optics all night long.

The kit comprises the AC377 Mini Controller with six temperature-control steps and either our 350mm (AC352) or 400mm (AC353) standard heating tape ­ see chart below for detailed specifications. The controller needs to be plugged in to a suitable 12 to 13.8V DC power supply available separately. The tape is a standard model and is plugged into the controller lead, and is then simply attached around the front of the optical tube with an elasticated Velcro strap. When assembled the total lead length is 2.8m (110"). The kit also includes a splitter plug to allow the use of an eyepiece anti-dew heater (see item AC350 or AC351 below). Note: the combined heater tape rating must not exceed 1.2amps which is the maximum continuous load of the Mini controller. The controller can be plugged into the Portable Astro Power Station (see above AC338), and at a typical low to mid-range heat setting the Power Station will keep your optics dew free for over 8 hours! Both kits require a suitable12 to13.8VDC power supply to function (not included in the price).

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socket
Heater extension cable
To extend heater power input cable

The heater extension cable is 1m (39") long and is designed to provide greater convenience in positioning heater tapes and heater controllers on larger instruments ­ especially longer focal length refractors and Newtonian reflectors. The extension cable plugs directly onto the end of the existing heater power cable, and has an anti-moisture shroud to protect the plug and socket connection.

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Auxiliary Cigar Lighter Socket
For direct battery terminal connection

The Auxiliary Cigar Lighter Socket is equipped with large crocodile clips that fasten directly to the terminals on a car, marine or leisure battery. The socket is un-fused.

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Socket splitters for input and output sockets
For direct battery terminal connection

Splitter plugs allow two connections to be made to one socket. The AC297 controller output splitter is useful for connecting more than 4 tapes to the Standard or Deluxe controller. In this way up to 4 splitters can be used to allow 8 tapes to be driven from the one controller!

The AC319 cigar lighter splitter allows any anti-dewing controller to be used with any other 12V accessory from just one cigar lighter output socket.

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telrad
Anti-Dewing Heater for Telrad™

The AC281 Anti-dewing heater has been designed exclusively to fit the popular Telrad reflex sight and provides dew protection for both optical elements. The heater fits at the inside base of the viewing window and generates enough heat to keep the lens and window dew free. The heater will easily shift accumulated dew if the heater was not switched on at the start of the session (see Flexible Dew Shields section for a Telrad fitting dew shield) The heater requires a controller and suitable power supply (see Controllers and Power Units below) and are not included with the tapes.

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blaster
Dew Blaster
Portable 12V Anti-Dew heat gun kit

A simple warm air gun to evaporate dew from optics. Warm enough to remove accumulated dew quickly. Kit includes 13amp 12V warm air gun with cigar lighter plug fitting and auxiliary cigar lighter socket with crocodile leads for speedy attachment to car or leisure battery. Warning, this product can deplete a weakened car battery with a couple of hours use to the point where the battery will fail to start the car! Not a cheerful discovery to make at the end an observing session we can assure you.

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Temperature regulating heater controller
Further information

Precise and stable temperature regulation is achieved using a proportional integral and derivative (PID) control algorithm coded into a RISC microprocessor. In simple terms, PID control uses the dynamic response of the heater system to the application of power, to predict the power level required to maintain the desired temperature. PID control allows the system to cope with a very broad range of dew heater and telescope combinations, and still give good temperature regulation with rapid stabilisation and minimal oscillation.

The user controls are relatively simple, consisting of three buttons and a variable-brightness four-digit dot matrix display. In addition to the manual controls, a serial interface (RS232) allows full remote control of anti-dewing functions on both main and auxiliary circuits. All control parameters are stored in an on-board non-volatile memory, which restores all parameters to previous values and maintains temperature regulation if activated at the time of the power-down.

The power to the heaters is controlled using a mark/space ratio switching technique incorporating radio frequency interference suppression. The controller outputs are designed to deliver a maximum total current of 6 amps.

Operating the controller

The controller comes supplied with two identical temperature sensors, which plug into the two 3.5mm jack connectors at the lower left-hand side of the unit marked Dew and Ref. The sensor connected to the upper Dew input measures the dew heater temperature, and should be fixed in good thermal contact with the telescope tube very close to, or preferably under, the dew heater tape on the main objective of the telescope. The sensor connected to the lower Ref input measures the ambient (or reference) temperature, and should be fixed to another part of the telescope. It should be placed at some distance from any dew heater tapes; it may be carefully positioned (away from external influences) in free air, but sheltered from the effects of wind, to monitor the ambient air temperature: the fork arm of an SCT would be a good typical position. The operating range of the temperature sensors is ­50 to +76 C. It is important that the sensors are connected to the correct inputs when temperature regulation is activated, as reversing them will eventually cause the TRHC to deliver full power to the heater in its attempt to achieve the desired temperature differential. Similarly, if the Dew sensor becomes dislodged from its position close to the dew heater, the controller will attempt to achieve the desired temperature differential by delivering full power to the heater.

For temperature differential regulation mode, the dew heater tape should be connected to one of the Main outputs. To start temperature regulation, use the menu button to enter the readout mode (see below) and use the and buttons to enter a differential temperature value. Temperature regulation starts immediately, provided both temperature sensors are connected to the controller. If one of the temperature sensors becomes disconnected during temperature regulation, the power to the heater tape is switched off until the sensor is re-connected. The main outputs may also be operated with or without temperature sensors in constant power mode (see main output power readout mode).

Heater tapes connected to the auxiliary outputs work in constant power mode. To set the power level, enter auxiliary output power readout mode (see below) and use the and buttons to enter a power level.

Menu operation

The various menu modes are accessed sequentially by pressing the central menu button on the front panel. Six menu modes are available, and pressing the menu button six times returns you to the initial mode. The and buttons are used to change the parameter values in the mode being displayed. The current menu mode is stored in non-volatile memory, so after a power down the display will return to the same mode. Each menu mode is identified by a character in the left hand column of the display as shown below:

D value readout mode

Dew sensor temperature readout

Reference temperature readout

P Main output power readout mode

A Auxiliary output power readout mode

BC&F Display brightness mode

readout mode

This mode displays the target temperature differential () in ºC which is used to regulate the temperature of the dew sensor above that of the reference sensor. The value may be decreased or increased by pressing the and buttons, respectively. Holding one of the buttons down causes the value to step in the desired direction. values are available in a range from 0 to 20 ºC. Setting the value to zero allows use of the main outputs in constant power mode ­ any other value automatically switches the main outputs into temperature regulating mode. The value is stored in non-volatile memory, so after a power down the current value will be restored.

Dew sensor temperature readout

This mode displays the current temperature of the dew sensor in ºC. If the temperature is negative, the in the left column is replaced with a "-" sign. If no sensor is connected to the Dew input a "?" is displayed. The and buttons have no action in this mode.

Reference sensor temperature readout

This mode displays the current temperature of the reference sensor in ºC. If the temperature is negative, the in the left column is replaced with a "-" sign. If no sensor is connected to the Ref input, a "?" is displayed. The and buttons have no action in this mode.

Main output power readout mode

This mode displays the current power level of the main outputs as a percentage ranging from 0% (power off) to 99% (maximum power). If the main outputs are in constant power mode (this requires the T value to be set to zero) the power may be decreased or increased by pressing the and buttons respectively. Holding one of the buttons down causes the value to step in the desired direction.

Auxiliary output power readout mode

This mode displays the current power level of the auxiliary outputs as a percentage ranging from 0% (power off) to 99% (maximum power). The power may be decreased or increased by pressing the and buttons respectively. Holding one of the buttons down causes the value to step in the desired direction. The auxiliary power level is stored in non-volatile memory, so after a power down the current value will be restored.

Display brightness mode

In this mode the display brightness may be decreased or increased by pressing the and buttons respectively. Holding one of the buttons down causes the brightness to step in the desired direction. The display brightness is stored in non-volatile memory, so after a power down the current brightness will be restored.

Remote operation

For remote operation of the TRHC, a bi-directional RS232 serial port interface is provided. This is connected to the serial interface via a standard 4-way modular jack connector, located on the bottom right of the unit. The full range of operating parameters can be controlled and interrogated using any simple terminal program directly via a dedicated serial port. A full list of command codes is given in the supplied instructions.

PC cables are available in the following lengths: 5m (AC424), 10m (AC150), 20m (AC269), 30m (AC140). Custom length cables can be made to order.

To overcome the need for a dedicated serial port, a jumper link is provided inside the unit next to the modular jack connector. By removing the jumper link and parking it on one of the pins, the RS232 transmit line is disconnected from the modular jack connector. With the transmit line disconnected; the controller serial connection can be "piggy-backed" on an existing serial connection used to control a telescope. Any telescope control program such as 'The Sky', that includes the Meade-type reticule brightness control or has an inbuilt terminal program, can be used to control the unit remotely. When used in this mode, the TRHC will react normally to commands, but the confirmatory and interrogation responses will not be received.

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