Noise associated with warm sensor temperatures during long-exposure shots usually has an effect of turning a supposedly black region into noisy and grainy one. In a typical DSLR, the imaging sensor heats up during exposure, causing its temperature to reach up to 10 deg C above ambient (with sensor temperatures reaching up to 35 to 40 deg C), further increasing the thermal noise. By cooling down the imaging sensor, it is possible to eliminate or somehow minimize this thermal noise.
Important: This project is a work-in-progress. Learn about the most recent modification attempts here. Links to other related prototypes are listed at the end of this article.
In this project, I will describe how I modified my Canon 450D DSLR to become a dedicated astronomical camera, with all functions intact including the auto-focus capabilities, and thus, may still be used for non-astronomical purposes.
Part of the modification is the replacement of the camera’s stock (built-in) filter with a Baader BCF. The filter allows greater sensitivity to H-alpha wavelengths emitted by most deep-sky objects, while at the same time eliminate unwanted UV and other IR wavelengths. This filter is necessary for any system that uses lenses in the optical train.
In my first prototype of a cooled DSLR camera, I used a Peltier module to directly cool down a Canon 450D’s imaging sensor, through cold plate (or cold finger) approach. Through this method, I was able to lower the temperature to up to 21 deg C below ambient, even when the camera is operating. To avoid issues related to condensation, the camera was equipped with nichrome wires to maintain the front of the sensor a few degrees above ambient (same principle in a dew heater).
To effectively dissipate heat buildup on the hot side of the Peltier module, I used an aluminum heat sink with a fan. I specifically used a magnetically-levitated fan (Sunon) mounted on rubber pads for this purpose to minimize vibration.
Below are some photos of the project during construction and detailed descriptions of some of the key steps in the modification.
This is still a work-in-progress. Results of field-tests conducted recently and actual shots taken with the camera will be discussed in my future posts. Clear skies!
For DIY astronomy projects useful for astrophotography, click here.
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