Telescope Mount Controller using PERSEUS-9

A telescope mount controller using PERSEUS-9 and it displays the coordinate system of a homemade telescope equatorial mount.

Similar projects worth following
I have developed a hardware and software system that displays the equatorial coordinate system of an astronomical telescope mount using the self-made computer PERSEUS-9. The features of this development are as follows.
1) The equatorial mount for the astronomical telescope is made by myself using a motorized rotary stage.
2) I made my own motor controller for an equatorial mount with a simple logic configuration.
3) Display the right ascension, declination and sidereal time of the equatorial mount on my homemade computer PERSEUS-9.
As a result, the self-built mount system obtained a slewing speed of up to 1024 times faster than the tracking speed and a positional accuracy of about 1% with respect to the amount of movement. A position display update rate of 1.1 times per second is obtained.

1. Concept

As a practical application of my PERSEUS-9 computer for astronomical observation, I decided to create a hardware and software system to display the celestial coordinate system of an equatorial mount. This computer is not suited to perform a large amount of processing at high speed because of its 1970s processing speed. Therefore, instead of controlling the mount from the computer side, the PERSEUS-9 reads and displays control status of the controller. From the button operation of the hand controller to the counting of motor drive and drive pulses, the system is configured with homemade hardware MCT-6. The count values are converted to angle values in right ascension (R.A.) and declination (Dec.) by CI-2, a homemade floating-point interpreter for PERSEUS-9, and displayed in real time.  No automatic GoTo action or polar axis correction from the computer side is performed. Figure 1 shows the MCT-6 and the computer PERSEUS-9, and Fig. 2 shows the homemade equatorial mount.

Fig. 1  MCT-6 the telescope mount controller and PERSEUS-9.

Fig.2  Homemade telescope equatorial mount with a 7.6cm refractor optical tube.

2. Equatorial mount

Another major challenge for me in this project was to build an equatorial mount that would be practical for my own visual observations. An equatorial mount has two orthogonal axes, one of which is the R.A. axis, which is parallel to the earth's axis of rotation. The R.A. axis rotates once every 24 hours, 56 minutes, and 4 seconds, which means that the telescope can automatically track a fixed star. This is known as tracking diurnal motion. Assuming that the telescope's observation resolution is about 1 arcsecond in angle, the vibration during tracking must be kept to less than a fraction of that in order for the star not to appear shaky. On the other hand, if the telescope is moved in a different direction to slew another object, the speed must be several hundred times higher than the tracking speed.

    There are difficulties in satisfying these two conditions simultaneously. For example, if such a speed change is achieved using a normal stepper motor drive system, the step period during diurnal motion tracking will be about once per second of time or once every 15 seconds of angle, and the tracking image will appear to shake violently. Therefore, if a micro-step drive method that divides the stepper motor steps into smaller steps is used, it is possible to perform fine driving of several tens to several hundreds of steps per second even during tracking. In this way, a drive system with sufficiently reduced vibration is generally constructed.

    It has also been difficult for me to prepare mechanical elements such as shafts, bearings, and worm gears that can withstand a certain amount of moment. So this time, I decided to see if I could solve this problem by using a commercially available motorized rotary stage. This motorized rotary stage is used for optical experiments and industrial applications and is expensive, but recently I found that it is available at a relatively low price through a certain mail-order site. Figure 3 shows the appearance of the motorized rotary stage used. This motorized rotary stage has a 60 mm diameter rotating part, and a 200 P/R stepper motor directly connected to a 90:1 worm gear. Both sides of the stage can be connected to other structures with M5 and M6 bolts.

Fig. 3  Motorized rotary stage Y200RA60.

    The appearance of the self-made equatorial mount is shown in Fig. 4. The structures on the equatorial mount other than the rotation stage were made of 100mm x 100mm, 10mm and 7mm thick aluminum materials that were machined and used. On top of the pillar connection body, the rotation stage of the R.A. axis is fixed to the face of the aluminum material, which is assembled to be perpendicular to the latitude value. On the rotary stage of R.A. upper surface, an L-shaped...

Read more »


Short version of CI-2 application software for displaying RA, DEC.

Adobe Portable Document Format - 21.25 kB - 06/11/2024 at 12:51



Mechanical drawings of the telescope mount.

Adobe Portable Document Format - 1.79 MB - 05/16/2024 at 09:16



Circuit diagram of the hand controller part of MCT-6.

Adobe Portable Document Format - 48.08 kB - 02/02/2024 at 14:08



Photo with the 15cm reflector optical tube weighing 4.7kg.

JPEG Image - 2.66 MB - 02/02/2024 at 10:52



Overall circuit diagram of the counting unit portion of MCT-6.

Adobe Portable Document Format - 122.41 kB - 02/02/2024 at 10:50


View all 9 files

  • 3 × SN74HC00 Logic ICs / Gates and Inverters
  • 2 × SN74HC04 Logic ICs / Buffers, Drivers, Transceivers
  • 1 × SN74HC14 Logic ICs / Buffers, Drivers, Transceivers
  • 2 × SN74HC138 Logic ICs / Decoders, Encoders, Multiplexers, Demultiplexers
  • 22 × SN74HC191 Logic ICs / Counters

View all 11 components

  • Telescope Mount Controller using PERSEUS-9 Log

    Mitsuru Yamada01/23/2024 at 12:46 0 comments

    1.  The article was first posted on Jan. 21, 2024.

    2. Revised on Jan. 23, 2024

        Added photo of aluminum materials in process to attachments.

    3. Revised on Jan. 25, 2024

        Added photo of the crystal oscillation section of the MCT-6 control unit.

    4. Revised on Feb. 2, 2024

        Added photo of a maximum payload of 15cm F4 reflector optical tube weighing 4.7kg to Files. 

        The counting unit circuit was modified so that the +5V power supply for the counting unit is supplied from the control unit.

    5. Revised on May. 16,2024

        Added a mechanical drawings of the telescope mount to the attachment files and added the link in the details body text.

    6. Revised on Jun. 11, 2024

        Added Chapter 7, Observation of globular clusters.

        Added a short version software MCT-6_1.TXT to the attachment files.

    7. Revised on Jun 13, 2024

        Added a Fig. 16, a sketch of globular cluster M10.

View project log

Enjoy this project?



David S wrote 01/25/2024 at 01:11 point

Is the purpose of this project to avoid using a laptop with auto guiding software? Why not control the motors with a more modern microcontroller, such as Arduino or Raspberry Pi? Or are you repurposing old hardware (which is awesome, BTW)? I'm just trying to understand the reason behind why you used the Perseus 9.

  Are you sure? yes | no

Mitsuru Yamada wrote 01/25/2024 at 01:48 point

Thank you for your comment. The purpose of each of my projects is to re-evaluate the early microcomputer technology of the 1970s. While today's developments in computer technology are impressive, I try not to lose sight of the basic theories and principles. I believe that the computer and electronic circuit technology of the time was somewhat simpler, making it easier to build from the principles up, and I have created a floating point interpreter calculation system using the same CPU that Apple and others used in their first computers in the 1970s, with built-in functions such as trigonometric and exponential functions. The system is my PERSEUS-9. The project is part of evaluating the validity of this system.

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates