The modification involves physically removing the “hot plate”, a kind of filter that blocks infrared light. Manufacturers install it in cameras in order to correct for the reddish hue inherent to CCD or CMOS sensors. Removing such filter makes the camera more sensitive to IR and as well as H-alpha wavelengths, which is particularly useful in deep-sky photography.

Modified Canon PowerShot S3IS camera

WARNING: I will not be responsible for any damage caused to your equipment. Follow instructions at your own risk!

I only used a screw driver to dismantle the camera, and then used a cutter to gently pry out the hot plate. It is secured in place with some sort of a double-sided tape or some form of an adhesive.  It took me 1 day to do all the task (which could have been done in an hour, but I wanted to go slow on this one so as not to make any mistakes). Just a note, be careful not to short any loose terminals especially the part of the circuit where the flashbulb is connected as it could literally fry the circuit board even when the batteries are not connected (the capacitor stores charge/power).

Removing the plate alters the light path such that it now focuses at a point a few millimeters in front of the sensor. Thus a replacement clear glass is needed to restore focus. If you do not have access to it, another option is to cut a few millimeters from the 3 plastic pillars that support the sensor. By doing so, you are actually moving it by a few millimeters closer to the lens, thus, focus is achieved. You may however, just remove the hot plate and leave it as is. Just use manual focusing. The only drawback would be difficulty in achieving focus at infinity.  It shouldn’t be a problem however,  if you will use it in conjunction with a telescope through afocal imaging as shown below:

Image taken with an IR-modified Canon S3IS through afocal imaging

While the camera was intended primarily for imaging targets at H-alpha and infrared wavelengths, as a consequence of the hardware modification, the camera now has an added feature typical to cameras with the hot plate removed, as shown below:

Through this modification, your photos will have a different feel, you can see through thin plastic, and you can take photos even in complete darkness (like the one you see in movies), using an infrared lamp.

I also took this opportunity to install a do-it-yourself (DIY) cable release to the camera. Each key in this numpad is connected electronically to a particular key on the camera. I resorted to this because I wanted to be able to operate that camera remotely while imaging. It’s a bit frustrating to lose a target simply because I ‘touched’ the camera. The cable release is connected via a 25-pin connector which could be clearly seen protruding from the side of the camera.

Do-it-yourself cable release

Wires leading to and from the camera

Canon S3IS modified for astrophotography: DIY hot plate removal, DIY adapter, and DIY cable release

Keep in mind however that by opening the camera, please understand the risks involved in the event of an accidental damage.

About CHDK

CHDK stands for Canon Hack Development Kit, a free software that can greatly enhance the capabilities of a number of Canon PowerShot cameras by overriding its native firmware (software). Through CHDK, you can unleash the full potential of your camera. It’s like teaching your camera new tricks: a point and shoot camera with full manual control on features normally locked by the manufacturer. For instance, a typical camera would only allow a maximum of 15 seconds exposure. Such short duration is not suitable for deep-sky imaging. With CHDK, it is possible to increase exposure time up to 10,000 seconds (up to 63 seconds only in earlier models). Since CHDK turns your point-and-shoot into a fully-programmable camera, it is possible, with the help of dedicated developers, to add a particular feature to address a particular need.

For more information about CHDK, you may visit the CHDK website at
http://chdk.wikia.com/wiki/CHDK
. For queries regarding the project, please leave a comment below.

Related link: Timing Occultations using Canon PowerShot S3IS and CHDK

For tutorials on how to get started with astrophotography, click here.

For DIY astronomy projects useful for astrophotography, click here.

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© Anthony Urbano (Manila, Philippines)

 

 

 

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