The Telescope Drive Master (TDM) is an extremely accurate drive correction system which is retrofitted to the "standard" model iEQ45 mount, increasing mechanical rotational tracking accuracy to approximately one arc second*. This betters the performance of mounts costing many times the price. The
Even the most expensive equatorial mounts, designed especially for advanced amateurs have some periodic and non-periodic tracking errors, which are impossible to eliminate from a mechanical standpoint.
While it is possible to reduce these errors using PEC (Periodic Error Correction), by recording variations causing by the worm gear which rotates the telescope along the polar axis, and then using them to guide out the errors, this has it's limitations because the worm gear errors themselves vary according to the loading or position of the mount, and other factors.
Therefore a "real-time" method of electronic correction is the only way to eliminate these errors for the ultimate in accurate tracking.
The TDM can make your iEQ45 mount perform way beyond it's mechanical tolerances by using a special high resolution optical encoder connected to the mount's RA axis. This enables you to use autoguiding which corrects for mechanical flexure in the optical train, as well as mechanical variations in the mount.
The combined result is incredibly accurate tracking and performance from the mount, which is now only limited only by the resolution of the telescope, your CCD camera pixel size, flexure in the mounting hardware and optical tube, atmospheric air currents, which cause star scintillation.
By using auto-guiding in addition to the TDM the effects of these errors are also reduced, which is why the TDM is compatible with auto-guiding. The high precision encoder unit is attached directly onto the Right Ascension shaft of the iEQ45 mount.
An electronic processor device receives the electrical signals arriving from the encoder unit and sends control impulses to the mount's motor drive, via its auto-guider input connector to compensate for RA drift. Because only one axis is affected (the RA axis), it is therefore important to make sure the telescope has very accurate polar alignment.
Please note that the unit effectively blocks the mount's polar scope, therefore polar alignment will need to be achieved using external software via your CC camera or manual drift alignment. There are several 3rd party software products which enable reasonably quick polar alignment (link below), therefore this isn't necessarily an issue, however we do recommend the TDM for use on a permanently mounted iEQ45, or for example a temporary setup where you polar align your mount and keep it aligned for a couple of imaging sessions.
The TDM unit comes with comprehensive installation instructions, and an adapter which attaches to the iEQ45 mount (you can de-select the adapter to buy the TDM unit only below). Necessary cables to connect to the iEQ45 are included.