Hi All,
Great forum, and very interesting to read. Not that I get a lot of time to loiter!
Whilst I've yet to purchase my first scope (looking at getting a Dob - but finances dictating the size). My question relates to trying to get some form of tracking facility attached to any future dobsonian. I had a friend many years back who had a 10 or 12 inch Dob, who had a worm drive attached to its basic Alt/Az mount. It wasn't a go-to nor any form of tracking device. It simply was a worm drive that as soon as you finished moving to any new position it would start tracking that object and keep it centred.
I've seen the Argo-Navis thingamajig and wished I could afford it. But to be honest I don't need anything that expensive.
Does anyone know of any web links to sites that can tell us how to build a simple worm drive of the type described above? or even purchase one that is relatively cheap?
For me I would just 'love' to by a Go-to but in Oz thats prohibitively expensive. I want the largest aperture I can afford so $'s to spend on the rest will be seriously depleted (I'll add what I can in later years), but having to continuously move the scope to keep up with a constantly moving object (from looking through other scopes) would be quite frustrating long term.
David
The issue with using worm drives on a dob is that you need 2 and they must work together and the rate that they work at will have to vary as an object moves across the sky. Think about an object that is in the northern hemisphere, for example M31. It will rise in the north east heading west, but for an alt az mount to track it, the mount will need to move both the alt and the az axes. When it reaches it's highest point the alt axis will momentarily not move at all and only the az will work then the alt will have to start up again, in the reverse direction. So simply putting worm gears on a dob without some sort of controlling circuitry will not work unless you are prepared to rig up something so you can manually operate them, but then it is probably easier to just push the dob!
Personally I would consider saving up for an Argo, brilliant bit of kit, easy to use with second to none customer support.
David, there are plenty of links for those with thinner pockets, but who have the wish and ability to DIY.
Try those: http://soundstepper.sourceforge.net/ ( I am using this system, low cost and very accurate, requires PC or lap running windows) http://www.bbastrodesigns.com/StepperSystem.html (I am still using this sytem on my dobson, requires cheap PC or lap running DOS)
There was a lot od disussion about this subject on this forum in the past.. see some links below (just tri search for "Bartels" or "Stepper motors".. or "GoTo dobson" or "encoders"..)
fficial&channel=sb&biw=1775&bih =752&tbm=isch&source=univ&sa=X&ei=D FxyVObALs3k8AWLwoGoCw&ved=0CBwQsAQ& q=encoders%20telescope%20images
