IMPORTANT (updated January 2016): This modification was pretty much useful during the time when parallel ports are still widely used. However, since parallel ports are now obsolete, this modification now suffers from major compatibility issues (simply because newer laptops no longer have parallel ports). I have written an update to this modification to allow the modified camera to be connected to newer laptops via USB ports (by using a USB-to-Serial Port adapter).

WARNING: I assume no responsibility for any damage caused to your camera/equipment by following the information presented here. Keep in mind that success cannot be guaranteed even if you have followed the instructions exactly as described. This modification must be attempted only with those who are comfortable working with electric circuits. Proceed with caution and follow instructions at your own risk.

A simple hardware modification allows the modest web camera to detect faint targets like galaxies and nebula by using a computer to externally control the camera’s exposure time. It involves severing some electrical connections and then soldering wires onto the camera’s circuit board in an attempt to bypass the web camera’s internal clock and image processor. This modification allows the web camera to take full advantage of its far more sensitive sensor — a CCD — to be used as an imaging camera, or as a dedicated guide camera for autoguiding purposes. In this article, I will describe how a Logitech Pro 4000/Logitech Pro 3000 can be modified for use in long-exposure and deep-sky photography.

A web camera modified for deep-sky/long-exposure photography

Below is a comparison between two images taken before and after the modification. An unmodified webcam (see left image) can only be exposed for a maximum of 1/5 of a second, too short to register an image in an extremely low-light situation (e.g., a room with the moonlight shining through a window as the only light source). A modified camera however (see right image), may be exposed for as long as desired (in this case, for about 60 seconds), and thus capable of collecting enough light to reveal ample amount of details. This newly-added feature is very useful for deep-sky photography where exposure of  a few minutes or more is not uncommon.

Shots taken before and after the modification: 1/5 second exposure (left), 60 seconds exposure (right)


This camera modification was based primarily on the original work of Steve Chambers, who was kind enough to freely share invaluable information to the astronomical community and asked nothing in return. To acknowledge this great contribution, this type of webcam modification and other succeeding modifications for that matter, have been named after him and have been given the ‘SC’ designation. The modification discussed in this article is what the astronomical community refers to as the SC 1 modification.

The circuit diagram I used in this modification was designed by Martin Burri. His design, particularly, the use of the 4066 bilateral switch has greatly simplified the circuitry of the module used for the long-exposure modification. His original diagram which appears in this page was used with his kind permission.

I have also based this modification on an article written by Andy Ellis. He has successfully modified a Logitech Pro 3000 web camera and provided a lot of useful information on how to proceed with the modification. His detailed instructions proved to be very helpful in completing the task.

If you were to attempt any web camera modification, I strongly encourage that you join the Quick Cam and Unconventional Imaging Astronomy Group (QCUIAG). Not only that you will have access to a huge amount of archived information regarding this topic, but you will also get to know like-minded individuals who are more than willing to extend help in any way possible.

Logitech 4000/3000 SC1 Modification

This modification applies for  both the Logitech Pro 4000 and the Logitech Pro 3000, since the two models are electrically identical. Test the camera first to make sure that it is working before attempting any modification. You may need to install the appropriate drivers supplied with the camera.

The modification requires the following tools and electrical components: (1) screwdriver, (2) fine-tip soldering iron, (3) soldering lead, (4) sharp cutter blade, (5) scissors, (6) glue stick, (7) super glue, (8) electrical tape, (9) fine wires, (10) 4066 bilateral switch, (11) IC socket for the 4066, (12) 4 pieces 15K resistors, (13) a length of telephone cable, (14) a DB25 male socket, and (15) a magnifying glass. Some optional components are: (16) a transparent plastic sheet, (17) clamping mechanism, (18) glue gun, (19) plastic housing, and (20) a multimeter.

The first task is to gain access to the circuit board by opening the cameras housing using a screwdriver. The two halves of the spherical case are held together by a single screw. Remove the screw then pull the two halves apart by applying a minimum amount of force.

Remove the screw to open the camera’s housing. Pull the two halves apart.

Connected to the circuit board are the microphone and the capture button which you may opt to remove. The camera will work just fine without these components. The lens and the CCD is mounted on one side of the board, while the two microchips we are interested in are mounted on the other side. The location of the Sony CXD1267AN and Philips SAA8116HL microchips are shown in the diagram below. A box marks the area where the modification will be carried out. Note also that I have used a clamping mechanism to hold the circuit board steady (you may just opt to tape the board securely on to a table if you don’t have a clamp).

Remove the microphone and the capture button. Locate the 2 critical components: the Philips SAA8116HL and the Sony CXD1267AN microchips.

Shown below are the two integrated circuits (or ICs, sometimes called microchips), the Philips SAA8116HL on the left, and the Sony CXD1267AN on the right. Marked also are 4 points of interests, A and B, and C and D. Points A and B are electrically connected; C and D are electrically connected as well. The blue lines map the actual electrical pathways. In this modification, we will attempt to sever (break) the connection between A and B, and as well as the connection between C and D. The precise points where the connection must be severed are marked by numbers 1 and 2.

Sever the connections mapped by the blue line precisely at points 1 (for C and D) and 2 (for A and B).

The connection between points C and D may be severed by carefully scraping the copper pathway that joins the two points. You may use a sharp cutter blade to complete this task. The image below shows a close-up view of the severed electrical pathway between points C and D.

Sever the connection between points C and D

Severing the connection between points A and B is a bit tricky. Instead of using a soldering iron, I just opted to use a sharp cutter blade to slowly cut through the relatively soft solder blob to somehow disconnect the IC’s pin number 4 from the circuit board. With extra care and using only the smallest amount of force, it is possible to successfully sever the connection with this method in just a matter of minutes, as shown in the image below.

Sever the connection between points A and B

Tap 4 separate wires onto each of the 4 points of interest A, B, C and D. Use a soldering iron with a very fine tip, and preferably rated at 20 to 30 watts to avoid applying excessive heat to the IC. In soldering very fine connections, I strongly recommend a technique called ‘reflow soldering’. Coat the wire’s tip with solder then let it cool. Use a few drops of super glue to secure the wire onto the back of the IC, then bend its tip such that it touches directly the solder blob where we want to make the connection. You can then use a soldering iron to apply heat onto the tip of the wire and as soon as the wire’s tip reaches a high-enough temperature, the solder blob underneath it will melt and flow (or reflow) to form a nice and clean joint. This is the most critical part of the modification and must be performed with the utmost care. You may need an hour to complete this task.

Solder very fine connections using a technique called ‘reflow soldering’.

Test the camera again by temporarily reestablishing the connections. You may also remove (optional) the green LED mounted on the circuit board to eliminate any possibility of stray light reaching the sensor.

Test the camera again by reestablishing the connections (left). Remove the green LED (right).

Use a transparent flexible plastic sheet to protect/cover the delicate connections and use glue as necessary. Just make sure to keep the pins neat and free from glue. For added sensitivity, you may opt to remove the IR-blocking filter of the camera. Remove two screws to gain access to the IR-blocking filter. Note that by doing so, the camera may no longer be suited for planetary imaging. This procedure however, is highly recommended if you intend to use the camera primarily as a guide camera.

Cover the delicate connections and use glue as necessary. Remove the IR-blocking filter if to be used as a guiding camera.

We now set this webcam aside and proceed on building the module that will make long-exposure imaging possible. We will get back to it as soon as the module is finished.

The Long-Exposure Module

Martin Burri’s circuit diagram below (used with permission) describes how to connect points A, B, C, and D to the 4066 bilateral switch. The 4066 receives 2 separate signals from a computer’s parallel port to momentarily ‘sever’ and ‘reconnect’ the path between A and B, and also between C and D. The 4 pull up resistors ensure that the ‘severed electrical paths’ remain ‘connected’ when no signal is received. We refer to this component as the long-exposure module. By default, the camera operates in ‘normal mode’ and can be set to ‘long-exposure mode’ whenever a signal is sent to the appropriate pins of the 4066 IC from the computer’s parallel port.

Martin Burri’s circuit diagram for the long-exposure module (used with permission)

To put things in context, I have prepared a diagram that describes how the components must be connected: the points A, B, C, and D on the web camera, the 4066 long-exposure module, and the 3 wires that lead to the computer’s parallel port.

A diagram illustrating how to interconnect the webcam, the long-exposure module, and the computer’s parallel port. Update: If you plan to use a Serial port, use this diagram instead.

The 4066 bilateral switch is a special type of electrical component that acts as an electronic switch. Take note of the orientation of both the IC and the socket by referring to the marker/indicator.

IC socket (left) and the 4066 IC (right)

The IC’s socket will serve as the main ‘assembly board’. With the socket faced-down on a table (take note of the pin numbers), solder the four 15K resistors on pins 5, 3, 2, and 13. Cut a length of wire (about 3 inches, preferably black) then solder it to pins 6 and 7. This wire will be connected later to the negative terminal of the webcam’s power supply. Pins 8, 9, 10, and 11 will not be used and may be trimmed off if desired.

Solder the four 15K resistors to pins 5, 3, 2, and 13. Solder a 3-inch long wire to pins 6 and 7. Trim pins 8, 9, 10, and 11.

Connect each end of the four 15K resistors together onto a length of wire (about 3 inches, preferably red). This wire will be connected later to the positive terminal of the webcam’s power supply. Connect pin 12 to pins 6 and 7 (negative terminal). Also, connect pin 14 to the positive terminal (red wire; along with the ends of the 4 resistors).

Solder each end of the four 15K resistors to pin 14 and onto the 3-inch wire. Connect pin 12 to pins 6 and 7.

A telephone cable has 4 insulated wires inside. We will only use 3 and then leave one wire spare (unused). Connect pins 6, 7, and 12 of the IC socket to the pin 21 of the DB25 male socket; pin 5 of the IC socket to the pin 5 of the DB25 male socket; and lastly, pin 13 of the IC socket to the pin 2 of the DB25 male socket.

Connect the 3 wires of the telephone cable to the 4066 IC socket (left) and to the DB25M socket (right).

Note however that the pin assignment for the shutter (blue wire) and the V-gate (white wire) is purely arbitrary. It means the shutter (blue wire), and the V-gate (white wire) for that matter, can be connected to any of the pins 2 to 9, for as long as you configure the software properly. Since in this particular modification I intend to use the K3CCD Tools for imaging and the GuideMaster for autoguiding, I have a few personal preferences on the pin assignment of the shutter (blue wire) and the V-gate (white wire). I have retained the pin assignment of the V-gate (white wire) leaving it connected to pin 2, but I have changed the pin assignment of the shutter (blue wire) and connect it not on pin 5, but on pin 3 instead. The pin assignment of the common ground (black wire) is also arbitrary since pins 21 to 25 are all electrically connected. I opted to connect the black wire (common ground) not on pin 21, but on pin 25 instead. If you have opted to follow my preferred pin assignment, then the camera should work well with the default settings of K3CCD Tools and GuideMaster with no additional tweaking required. The image below shows the final wiring diagram of my setup.

Preferred pin assignment for my setup: V-gate (white wire) to pin 2, shutter (blue wire) to pin 3, common ground (black wire) to 25.

Now that the long-exposure module is almost complete, we can now connect it to the webcam’s circuit board: connect point A of the webcam to pin 4 of the IC socket; point B to pin 3, point C to pin 1, and then point D to pin 2. The 4066 draws power directly from the USB cable: connect the positive terminal (red wire) to the +5V line and then the negative terminal (black wire) to the common ground.

Connecting the long-exposure module to the web camera

Carefully place the 4066 IC into its socket. Observe correct orientation. Double check all connections.

Place the 4066 IC into its socket

Use electrical tape to insulate all exposed wires.

Photo of the long-exposure module

Another photo of the long-exposure module

You may opt to house the whole assembly into another casing. Incase you wish to retain the original casing, you need to drill a hole for the ‘parallel-port cable’. The original housing should be able to accommodate all the newly-added components.

Drill a hole for the ‘parallel-port cable’. The camera’s original housing should be large enough to fit all the newly-added components

The camera is now ready for testing.

The parallel port (left), the DB25M connector (center), the web camera (right)

Testing the Camera

To test the camera, download and install the program K3CCD Tools by Peter Katreniak. Connect the web camera to the computer via the USB port and the parallel port then launch K3CCD Tools. Images may be captured by clicking on the ‘Long-exposure’ icon, setting the desired exposure time, and then clicking the ‘preview’, ‘record’, and ‘playback’ button. Images captured are saved by default on the My Documents folder (for Win XP).

To capture an image, click on the ‘Long-exposure’ icon, set the desired exposure time, and then click the ‘preview’, ‘record’, and ‘playback’ button.

For autoguiding purposes using the program GuideMaster by Matthias Garzarolli, the following are the recommended settings for the Guiding Imager tab. Detailed instructions on setting up a guiding camera may be found here.

Recommended settings for the Guiding Imager tab

The following are some raw (unprocessed) test images:

30 seconds exposure

dark frame at 30 seconds

60 seconds exposure

dark frame at 60 seconds

Here is a detailed comparison of images taken before and after the modification, and the use of the dark frame to subtract the electrical noise (hot pixels) from the image. The bottom row images (d, e, and f) were taken with the camera set to ‘normal mode’ and the top row images (a, b, and c) were taken with the camera set to ‘long-exposure mode’.

Top: (a) 30 seconds exposure, (b) dark frame for 30 seconds, (c) dark frame subtraction; Bottom: (d) 1/5 second exposure, (e) dark frame for 1/5 second, (f) dark frame subtraction

If you have questions, feel free to leave a comment. Clear skies!

Related articles:
DIY Logitech 4000 SC1 modification (Serial Port)
DIY Autoguider: Home-Built Autoguider Project

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© Anthony Urbano (Manila, Philippines)