[Note April 11, 2001:  This page is for technical information only.   We have discontinued the ST-4 and are now sold out of our remaining stock.   For the next generation of autoguider / imaging camera please see the STV.]

Very few instruments have had the dramatic effect on astrophotography as the Model ST-4 CCD Imaging Camera/Autoguider. This thermoelectrically cooled CCD imaging camera is actually a dual purpose instrument that can be used as an automatic Star Tracker to take long guided exposures of the night sky or, in conjunction with a personal computer; as an introductory level Imaging Camera displaying 8 bit digital images.  The internal cooling of the CCD reduces the detector thermal noise and significantly improves the ability to guide on dim stars. The ST-4 is easy to use and will automatically track a guide star for professional quality astrophotographs, measure stellar magnitude, perform as a blink comparator or record images of galaxies.

When located at the prime focus of either a guide telescope or the primary telescope, the Model ST-4 generates control signals for guiding a telescope in Right Ascension and Declination. In operation a guide star is focused on the CCD detector; which consists of an array of elements, called pixels. These pixels, which are arranged in horizontal and vertical rows, convert photons into electrons. When a guide star's image is present at a specific pixel the ST-4's microcontroller will note the increased signal from that pixel. If the star is drifting it will appear at a different pixel in the next exposure. The microcontroller then calculates how far the star has drifted and generates a control signal to correct the position. The control signal's duration is a function of how far the star has drifted. The microcontroller can take an exposure, read out all of the pixel values, and calculate the necessary telescope correction in less than a second.

The ST-4 has a CALIBRATE mode in which the internal software automatically drives the telescope in all four directions sequentially. During this mode the ST-4 determines the amount of correction necessary to move the guide star one pixel in the North, South, East and West directions of the field of view. Once the CALIBRATE function has been completed the user presses the TRACK button and the ST-4 acquires a fresh star image, centers the image on a pixel and holds that star in position by constantly monitoring it and sending correction signals to the telescope drive immediately after each exposure. 

M51. Seven 1200 second Model ST-7 CCD images summed together and taken at the prime focus of a Celestron C14 at f/7.

The ST-4 is thermoelectrically cooled to enhance its sensitivity to dim stars. This extreme sensitivity enables guide stars as faint as 8th magnitude to be tracked utilizing a 60 mm guide telescope and 12th magnitude with a 20 cm aperture. The rapid calculating power of the microcomputer enables the guide star location to be determined within a fraction of a pixel, enabling better than 1 arcsecond tracking accuracy.

NGC2244. Two 60 minute integrated Model ST-4 autoguided astrophotographs taken on Tech Pan Film with a 120 format camera.

In the IMAGING mode, when used in conjunction with a PC or Macintosh, the ST-4 will record and display 8 bit digital images that are "seeing" limited.  It can be used for imaging faint galaxies, measuring the angular separation and orientation of close binary stars or determining the magnitude of any star within its field-of-view. A cable is provided to connect the Model ST-4 to the serial port on the host computer as is software to automatically configure the port. The microcontroller in the ST-4 is instructed to take an exposure by the host computer and to store the data in its internal memory. Complete control of the imaging camera is through the computer keyboard. The data is then transmitted over the RS-232 serial link at speeds up to 57.6K baud to the computer where it can be displayed and saved to the disk. A full image consists of 31872 bytes and is digitized to 8 bit accuracy.

The ST-4 now includes several additional software programs which greatly expand on it's capabilities as a stand alone autoguider.  When connected to a computer or laptop via the serial port, the ST-4 becomes a versatile instrument.  For remote operation the ST-4 now comes with CCDTRACK software which allows the user to perform all of the ST-4's stand alone guiding functions from a remote computer.  CCDTRACK software also includes several enhancements to the ST-4's guiding capabilities.  Remote control is very useful for observatory work or any application where the user wishes to manage the autoguider and telescope from more than a few feet away.  CCDBLINK software allows the ST-4 to be used as a very accurate blink comparator as might be used for asteroid hunting, comet tracking, etc.  CCDUTIL software contains image processing utilities and special file utilities for interchanging image files from the ST-4 with other programs.  The utilities include image translation and rotation with sub-pixel accuracy, flat field correction of images, filtering and scaling.  

The Model ST-4 is in world wide use. It has become the standard for precision telescope guiding. It is also a good low cost introductory imaging camera, but the autoguiding is the major feature of this product. Call us with questions about interfacing it to your telescope.

Model ST-4 CCD Specifications

Readout Specifications

Optical Specifications (8" f/10)

System Specifications

Physical Dimensions

Revised: April 10, 2002 01:36:12 PM.
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