Telescope Drive Master

Driven to Perfection…

The Telescope Drive Master, or TDM, is the vision of accomplished Hungarian amateur astronomers, Istvan Papp & Attila Madai of MDA Telescoop. It was their desire to solve the problem of tracking imperfections that, to some degree or another, are inherent in all equatorial mounts, and the Telescope Drive Master was the result. The TDM is designed to attach to popularly available equatorial mounts, such as the Celestron CGE & CGE Pro, as well as mounts by Synta, iOptron, and Meade. The Telescope Drive Master™ (TDM) uses a mount-specific adapter, an ultra-high resolution encoder, and an electronics package that transforms your drive system into a super-performance, research-grade drive. This device does not require tedious PEC training. Just turning on the TDM eliminates nearly all of the periodic and non-periodic tracking error of your equatorial mount.

How does the Explore Scientific TDM Work?

The Telescope Master Drive electronic controller unit compares the incoming signals from the high precision rotary encoder, which is mounted onto the RA shaft, with the time signal of its quartz oscillator. Any deviations of the angular velocity of the RA shaft from the prescribed drive rate are compensated by feedback regulation in real time by accelerating or slowing down the drive. If further correction is needed because of errors other than periodic drive error, the TDM allows auto-guider input as well.

How Much Better Can My Drive Perform with the TDM Installed?

A typical drive on a moderately-priced equatorial mount can easily have 20-30 arc seconds (or more) of periodic error. The Telescope Drive Master can easily improve it down to 2-to-2.5 arc-seconds peak-to-valley or less, which is what you would expect from equatorial mounts that cost many thousands of dollars. However, it is possible to get even better performance with the TDM. Attila Madai explains:

"TDM’s control range is +/-0.5 arc-seconds (or 1” ptv) in more than 95% of the exposure times in optimal cases. The user needs to test and adjust the guide control speed of the Hand Controller (e.g. Autostar), which fits to Controller-TDM combo on the best way. (Optimum point can be found between 0.15x and 0.5x sidereal speed; depending on the mechanical behaviour of certain mount and monitoring frequency of HC’s guide input port)."

What are Typical Results from the TDM?

Most users of the TDM are making unguided images of up to 20 minutes or more in a single exposure with perfectly round stars. Here are some examples of long-exposure, unguided astrophotos taken with the TDM installed:

How Can I Test the Performance of my Drive?

You can download TDM Monitor Software free of charge! This program can read TDM correction values in real-time via the PC serial port (or via RS232-USB adapter) from USART Port of TDM box.

The installation package contains the LabView runtime environment as well for using this application. In this way, the user can check the tracking error of any mount in real time in his/her warm room (without autoguider support).

There are two versions of TDM Monitor: v1.0 with +/-16" (1/8" resolution) or v2.31. Both have +/-16" (1/8" resolution) and +/-32" (1/4" resolution) range of tracking deviation display. Before installation, it is recommended to read "ReadMeFirst.txt" file.

Why Would You Invest in Improving Your Drive?

"I remember learning the techniques of making an astro-photograph through long exposures on film. It was a tedious process of learning how to properly guide on a star. Most of my exposures were 30 minutes or longer, and on the rare occasion that I was able to keep my guide star perfectly centered in the crosshairs of my high-power eyepiece to produce an astrophoto that I was willing to show to others, I felt that I had conquered Mt. Everest!

The problem was that my equatorial mount had significant periodic error, which caused me to chase the movement of the star in the crosshair, by making rapid button presses to the drive corrector hand-controller. You had to learn the rhythm of the error in order to anticipate which button that you were going to press next. Over the years, I improved but I never fully mastered manual guiding, so my good astrophotos were few and far between.

When astronomical CCD cameras became available, the exposure times became much shorter, so other problems, such as getting a proper focus, proper centering of the object in the field of view, and proper exposure became much easier to manage, because you could see the results right away, but the problem of drive errors still plagued astrophotographers. The only solution at that time was to invest in a better mount, and perhaps, an autoguider. Software was also developed to help improve the periodic error control (PEC), but training the drive with software to get the best results required a bit of skill and a lot of patience. Even with the advance of PEC software, it is still not easy to make top-quality astrophotos using most of the popular equatorial mounts available today.

However, if you could improve the tracking accuracy of the mount by eliminating most of the large-scale drive errors, then your energy would be focused towards improving the skills of acquiring the images and image processing, instead of fighting drive errors in your mount. This is what the Telescope Drive Master can do.

Frankly, I think that every equatorial mount should have one attached to it, because the Telescope Drive Master is one of the easiest and most effective ways to improve your astrophotography. I just wished that I had one for my telescope twenty years ago, but I will say that it has been worth the wait!" --Scott Roberts

Jerry Hubbell and the TDM

In my opinion, the TDM is the perfect solution for portable observatories. Because it allows you to setup quickly and start imaging right away, you don't worry about your mounts tracking ability, or it's performance... It just works. 

"The unit required 30 minutes to install (only because I did not take the 16-inch LX200 apart). The Telescope Drive Master was turned on and started working immediately while my supernova run was activated, at 72 images an hour.

The initial result: 90% of my images had no guiding error with the TDM running. My 16-inch LX200 Classic has no PEC on the internal chips, (so my yield of perfectly round stars without some sort of guiding assist is very few). This makes it a worst-case scenario for the Drive Master to correct!"

The TDM performance

The TDM performance measured on the EQ6 Pro mount. Click image for full size view.

A close-up of M13 - The Great Hercules Cluster

A 10x90 second stack unguided using the Carbon Fiber ED127 Air-Spaced Triplet and the Telescope Drive Master. Click here for the full size image.

Jerry Hubbell and TDM software

- Hubbell TDM TE Recorder User Guide ver. 1.0.2
- Hubbell TDM TE Recorder Software Installation ver. 1.0.6b (Windows zip file)

This software is a beta test version, please forward all questions to Jerry Hubbell via email.