Hi everyone. I'm in the process of designing a telescope mount, and am now trying to figure out how to drive the thing. Ideally I would like to go with an off the shelf dc motor and gearhead setup, as this appears to be the cheapest option. My problem is, that I don't know how slowly you can run a dc motor before you start to cause issues - like cogging, or maybe burn-out, or who knows what. So I was hoping that you guys could give me some pointers.... Here's some specs that I think are required: -The system must turn at around 1 revolution per day. -Start-up torque, with safety factor included, is about 20Ncm. -Normal running torque will be significantly less than above. -Budget is around AU$200 per axis (this is the main problem!) Stepper motors are not an option, unless someone can help me prove that the cogging of a micro-stepped stepper is comparable or less than that of a standard dc motor. Becuase I've come in on this project three quarters of the way through, I'm a bit limited by the design so far - so a great big worm gear arrangement probably will be a little too tricky to implement (and would play havoc with the budget too I think). I guess what I would primarily like to know (at this stage ) is how to figure out how slow a dc motor can safely go given the data provided by manufacturers such as mclennan.co.uk and pittmannet.com. I'm sure there are a million other questions too, but I just don't know them yet! I've trawled the net and various textbooks too, so if anyone can suggest some good texts etc, that would be great.