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300D (Digital Rebel) For Astrophotography?


jim_mueller2

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As a 10D owner, I'm a bit confused with the use of the 10D's sensor (and the 300D's) for Astrophotography. I assume this type of photography has exposures measured in minutes, and from the literature I've read, exposures running passed four minutes tend to give poorer results. It had something to do with some kind of amplifier mounted near one of the corners of the camera's sensor that, when exposed for many minutes, tended to heat up, causing markedly increased noise in that corner of the frame. The problem was more pronounced in non-Canon cameras, as the amplifier was mounted right near the sensor. Though it was less of a problem in Canon's 10D, thanks to Canon engineers who, aware of the problem, mounted the device farther away from the sensor to avoid the heat-caused noise, it was still something unavoidable in longer exposures.

 

I'm curious to know more...

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I have experienced a problem with my 300D that sounds like what you described. With exposures longer than 2 minutes, a red shading begins to appear in the bottom left corner. At 10 minute exposures (especially at higher ISO's), it can take up to 5-10% of the frame. I'm not convinced that all 300D's experience this, and I've certainly seen 10D long exposure examples that do not experience this problem, so mine is at the Canon service depot at the moment. Assuming this is just an anomaly, my other experiences are that the 300D lacks mirror lockup which the 10D has, possibly making a difference on the long exposures.
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My understanding is that for really long exposures MLU is not a requirement. It is for shorter exposures, where the exposure is mostly or entirely accomplished during the time the mirror has excited the mount, that it has value. If I understand correctly. This certainly seems to be my experience.
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