Motorising Dob mounts

[pepston]

If any DIY geeks out there have fitted motors to a Dobsonian mount I would be most greatful for any advice on how you geniuses did it.

I`d thought about purchasing a couple of windscreen wiper motors from a scrapyard and gearing them down further to acquire the required speed of travel on the base. I have to stress that every piece of my scope is handbuilt so anything can be customised. I can control motors fairly easily via electronic gadgetry. My quandry at present is the transmission of the power to the said base for rotation and to the pivotal point of the vertical axis. I`m not that concerned about perfect tracking as I`m only observing Lunar and Planetary objects at the moment and taking images using a webcam then using software to overlay etc. Any input is warmly welcome.

[NGC 1502]

Not exactly what you are asking, but another route is to buy or make an equatorial platform - http://www.equatorial-platforms-uk.co.uk/

Regards, Ed.

[skybadger]

In my opinion windscreen motors would be too powerful and large. I use them for the dome.

Their gearing also puts them at one rev about every 3 secs through the output worm wheel. So you still have alot of gearing down to do.

PIck a smaller stepper or servo motor and apply some judicious gearing to get the step size or pulse width modulation controllable and work out whether you want to do alt-az driven to match RA motion or a dobsonian platform.

Cheers

Mike

[pepston]

Mike/ Skybadger, many thanks. I didn`t realise that windscreen wiper motors were that powerful so obviously vibration would be an issue there. Also gearing. The idea of stepper motors has crossed my mind but I just did not consider them poweful enough. I`ll lighten the load on the mount I think by holesawing and reducing the weight without compromising the integrity of the structure but I`ll leave the base as it is for the moment and with the addition of bearings rather than teflon bushes I`ll get less rotational friction. Do you know of a company that could supply steppers?

Ed/NGC 1502 Had a look at site link you sent and am seriously considering equatorial now as it eliminates the one plane of control I was most concerned about and I`m sure I could modify my base plate to accommodate. I looked at equatorias website but they are out of stock on products and limited information as to how their idea works but it was well worth the browse. I thank you both.

[NGC 1502]

Link here to DIY equatorial platforms - http://stellafane.org/misc/links.html#EquatorialPlatforms

Hope it's useful, Ed.