Equatorial (paralactic) platform help to use no motion telesopes eg. dobson style telescopes. Just put on platform Your favorite dobson and enjoy stable magnificated picture during minutes. "Equatorial" in name means that platform symulate daily Earth moving so in efect this moving is compensated and telescope point still the same place on sky. My platform has unique technical solution called 'one point south bearing' and construction is simply but this way is also very accurate and reliable. Basic elements are made with plywood, brass and polycarbonate on CNC machines. Main parameters are the following: running time about 70 minutes rewind time about 3 seconds load capacity up to 35 kg latitude 47-55 degrees (nominal is 51 degrees) weight 8kg dimensions 630/680/200mm power supply 9-14V/1A stepper motor diven by programable quartz generator
Equatorial platform consist with 2 main parts: top and bottom plates. Shape of both parts looks as big T letter and this way easy can be oriented before using. Wider part (T letter bar) is called NORTH side and narrowed side is called SOUTH side. Similary, NORTH platform side should be oriented to North direction (Polar Star direction) and SOUTH side to South direction. For simple visual observations is enought to rough setting platform along North - South line. You can use as well compass.
Bottom plate stand on 3 regulated legs and carrying most of elements: regulated legs allow to adopt to local latitude two rubber rollers ensure correct run of top plate stepper motor drive active roller programable generator/driver ensure precise and exactly steering signal runing limiter setting working range brass pivot establish proper position of top plate Stepper motor has 7.5 deg rate (48 steps/revolution) and inner gear with rete 1:120.
One point south bearing means that, in oposition to traditional solution with bigger south sector and two bearing rollers, this construction use as bearing brass pivot with small ball at the end and brass nest with ball hole. This way position of running plate is always unequivocal and accurate and all manipulation during setup and rewinding are as easy and save as never before. As the effect top plate is supported in three point guarantied stability.
Heart of drive system is EQ Tracker. It is combination of programable quartz generator and microstepper driver. Quartz generator coming from another project called AstroPilot and has possibility to setup steering frequency with two buttons and one digit display. Microstepper driver can divide one step on 1:1 to 1:128 range and gives stepper motor precision to make platform running smooth enought for biggest magnifications and astrofotography. Default microstep rate is 1:32. EQ Tracker inerface has 4 buttons and one digit display. Two gray buttons working in second (De) ax and has no role in basic platform. Red button is mode button and green button working as Enter button for action confirmation. EQ tracker is ready to use, just power it on with 9-14V/1A and enjoy of sky beauty but in some cases, specially in astrofotography, system can be regulated more precisly and accurate. Follow the link to check how can You do it Yourself. EQ Tracker can drive two stepper motors for Ra i De axes but basic model has only one port for Ra ax motor. Basic model can be expanded to full model any time. Another end of EQ Tracker has power suply socket and guide port. Power supply should be 9-14V/1A. It could be battery or another power source 9-14V with minimal efficiency 1A (voltage need not to be stabilised but it's adviced). Guide port working properly in modes 6-8 but probably most usefull is in mode 7 (sideral tracking). Full guideing is possible of course in two ax model but even one ax allow to control Ra ax speed with GuideDog, GuideMaster or SBIG relay guide systems. Measured accuracy under guide control has level of 1-2 arcsec. More about it You can read in the following link.
Power suply cable, spare power plug and transport shield are the three additional elements in eq platform set. Cable You can connect directly to battery. Spare power plug can help adopt Your power supply. Transport shield allow safely carrying eq platform. Shield is aplicated on north side of platform. When shield is on place then runners and rollers lost directly contact so this way life of that elements became longer. Rubber holder stabilise shield on place and central screw keeps both plates together and platform can be carrying in one piece by holding on brass pivot.