ETX TECHNICAL TIPS Last updated: 15 February 2005

ETX-70 electronic focuser

Sent:	Saturday, February 12, 2005 06:33:04
From:	Mirko Mattioli (smtfun@aliceposta.it)
it will be a great pleasure if you can to publish this memo on your ETX
web site. It's concernig a homemade electronic focuser for ETX-70 (but
probably works also on ETX-60) with very common components for a few
dollars. Hereby in detail.

"Specially when I use a webcam on my ETX-70 Telescope, is very difficult
(impossible?) to reach a good focus, due a movements of the mounting. On
the market I never found an electronic focuser, so I have decided to
build one myself. The philosopy was to use common materials at
low/effordable cost (sometimes with the right materials the cost is
below than "flexible" focuser knob on the market). This project is based
on a stepper motor in order to achive a precise focus using a digital
control pad, with the possibility to connect the system with a PC for
remote control and for save/load the focus positions usually used (i.e.
whith different eyepieces, or particular regions of the sky). The
stepper motor cames from "floppy drive" of the personal computer (a
new/sealed floppy drive = 10-15 USD) and it is interface with a
microcontroller (PIC or ATMEL = 10 USD) closed in a plastic enclosure
with 4 push-buttons ( movement +, movement-, fast movement +,fast
movement -) and with a 9 pin connector for serial cable to PC (cost = 10
USD). It's necessary to build a bracket in order to attach the stepper
motor; this bracket can be made from the alluminum cover of floppy disk;
the bracket will be fix near the original focus knob of etx (due the
small size of stepper motor), with the two screws above and below the
focus knob (see my datasheets for detail). Than is necessary di fitting
the stepper motor shaft with the focuser shaft of ETX telescope,
remouving the original knob. And that's it ! I don't have a personal web
page, so please e-mail me at smtfun@aliceposta.it for datasheets,
materials, microcontroller and pc software (if you need the
microcontroller already programmed and/or already soldered on electronic
circuit boad, please let me know: I will be very happy to send them to
you at the cost, NO extra-charge (max 40-50 USD).
Enjoy, Mirko"
 
Thanks and regards,
Mattioli Mirko - Italy

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