Grampian Stars 37.11 Sth. 142.36 Est.
	Grampian Stars ATM Mods

ATM Mechanical Goto Modifications

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Mel Bartel's Goto Drive Front Panel

Built by Richard Fobister

The Drive Controller with all components installed, including ammeter, voltmeter, power switch, motor connections, power plugs, handpad RJ12 connection, reverse polarity protection and parallel port connection, is built to exacting standards by Richard located in Canberra Australia. The double sided control board is sourced from Mel Bartel in the USA.

Mel Bartel's Goto Drive Rear Panel

Built by Richard Fobister

The front and rear panel pictures are taken from a system, built by Richard, that has an optional autoguider relay board, an encoder board and an automated focuser that uses the optional field derotator circuit. The excellent software scope.exe, designed and written by Mel Bartel, is free and can be downloaded from his web site.

Stepper Motor 1.8 deg. Step Angle

Chasing down and choosing stepper motors, The motors I chose were both 500mNm (70 oz-in) holding torque, frame size 23, rated at 5.1V, 1A, 8-wires and 1.8 degree step angle,(ie: 200 steps per revolution). I bought two of them from RS Components part number (440-442). The motors are 4 phase construction resulting in a much higher working torque whilst maintaining very high resolution due to the small step angle.

Wiring Diagram

A data sheet showing the wiring diagram for the motor came in the package which saved a lot of time trying to figure out the connections

Gearbox Adaptable 4Nm

I chose RS Components gearboxes. Part number (718-852) a 5:1 ratio 4Nm gearbox, sintered bronze bearings and sealed output shaft, of robust metal construction for high reliability, performance and positional accuracy. They easily fit to the standard frame size stepper motors with an adaptor kit, part number (718-953), which contains the drive pinion (small cog) to go onto the motor shaft and engage with the gearbox. The 5:1 ratio is a little high resulting in slower slew speeds and finer arcsec per microstep. Ideal for immaging with a ccd camera.

Installation

The drive pinion (3) is glued on to the motor shaft with LOCTITE 601, a high strength adhesive, to a critical depth of 12.5mm as shown to mesh freely with the first gearwheel in the gearhead..

Great Inspirations and ideas are had from ScopeDrive a forum to discuss topics related to Mel Bartels' computerized telescope control system, also check out RoboScope a forum to discuss topics related to creative GOTO projects of any kind.

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