Here’s an upgrade of my previous TEC-cooled 450D project. It uses a cold copper plate mounted directly at the back of the imaging sensor, which is then cooled by a stack of 2 Peltiers, one being more powerful than the other (40 mm and 30 mm modules). Non-electrically conductive thermal paste (Zalman) has been used to promote effective heat transfer and yet avoid electrical hazard. A12V 12A DC adapter powers the fan, Peltiers, and the heater. A standard Canon adapter powers the camera.
I’ve decided to seal the camera in an airtight case (Lock and Lock), and remove the stock filter as well as the dust-cleaning filter. A 2-inch Baader UV-IR filter serves as the airtight chamber’s optical window in front of the imaging sensor, with nichrome wire heaters to prevent formation of dew. Initial tests show that the desiccants placed inside the sealed chamber were successful in drying the air and completely prevent condensation on the sensor itself. All gaps, including the thread of the filter, are sealed with melted plastic (glue stick), to ensure perfect seal.
The whole assembly was then housed in a rigid plastic box to serve as a support structure for the heat sink and fan and to provide protection as well as eliminate clutter. A 1.25 inch T-adapter provides a means of connecting the camera to a telescope. Since the adapter is mounted directly onto the rigid box, it can actually be replaced with other types of adapter to accommodate other preferences (e.g., a means to connect with standard Canon lenses). Special attention was given to ensure that proper spacing was maintained between the sensor and the front side of the housing so that the camera could still reach focus when the current T-adapter was eventually replaced with a custom-fabricated adapter for Canon lenses (I have yet to visit a machine shop for this).
The camera can be connected to a computer (USB) through a port mounted on the side of the housing, or may be operated as a stand-alone unit through a cable release port. I have also fitted a clear glass window to gain access to the LCD display and have rewired the buttons onto external keypad/switches.
I have not measured with a thermometer how low it can go, but I could see ice forming on the cold side of the smaller Peltier. Initial dark frames/images taken during active cooling show an apparent decrease in noise.
To view other my other DSLR modification projects, follow the links below:
August 2014 Modified Canon 450D DSLR for Astro-imaging (improved sealed chamber prototype)
March 2014 Modified Canon 450D DSLR for Astro-imaging (sealed chamber prototype)
February 2014 Modified Canon 1000D DSLR (Baader BCF filter replacement)
December 2013 Modified Canon 450D DSLR for Astro-imaging (custom-fabricated lens mount)
November 2013 Modified Canon 450D DSLR for Astro-imaging (sealed chamber prototype)
February 2013 Modified Canon 450D DSLR for Astro-imaging
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© Anthony Urbano (Manila, Philippines)