I've been looking into long exposure photography for star tracking. How does it negatively (if at all) affect your camera?
There might be some repercussions, especially on very cold or hot nights. Long exposures and continuous use of the sensor does cause it to heat up. This is really not that much of a problem for most modern cameras as they have adequate heat sinks and other features to bleed off heat and prevent too much buildup. (Some newer cameras may even prevent you from starting a new shot for a while if it detects the sensor is too hot.)
On extremely cold nights, you might encounter some trouble with your batteries, as cold tends to reduce their effectiveness and life. Poor current flow can occur during extremely cold or very hot nights, which can mess with the camera's electronics itself. This sometimes manifests as funky menu behavior and the like. I have not seen any permanent damage from such a thing, but I have also never spent a truly extensive amount of time photographing in very cold weather (probably the longest was during a total lunar eclipse which spanned several hours in sub-freezing temps.)
LCD displays perform poorly in very cold environments as well, and can end up damaged due to extreme cold. Most normal cold temperatures won't be a problem, but sub-freezing temps with an added windchill can bleed off every scrap of energy held in a camera, sometimes resulting in dead LCD pixels or possibly worse damage. Normally, you'll encounter problems due to poor battery performance, however if you are doing something like taking a time-lapse sequence of shots over the duration of a whole night, and intend to sleep through much of the night...you might want to pick nights that are not extremely cold. There really is no telling what super cold temperatures might do to your equipment if its exposed for an extended duration of time.
Weather sealed gear is obviously going to hold up better in more abusive conditions, however most sealed gear is only available in the top of the line equipment. Most cheaper gear has minimal weather sealing or resistance features, if it has any at all.
As you hold open the shutter and maintain the exposure, there is heat build up on the sensor and this will translate into noise in the image, but I'm not aware of any long term negative effects resulting from this. I've personally done up to an hour on an exposure in bulb mode, many times, and I've never encountered any ill effects to the camera.
So, unless the manual has a warning about this, I wouldn't be worried about it.
As John Cavan has said, the camera sensor probably won't get any damage from the long exposures.
But keep in mind that keeping the camera itself exposed to the elements for long periods increase the chances of bad things happening to it. For example:
- Rain/Snow/Wind/Animals can hit the camera/tripod in a bad way.
- Too low temperatures can cause some impact to the batteries and some components of the camera.
- Someone may consider that camera quite a catch if found alone in the dark... :o)
In this video, sunlight destroys a cmos sensor. https://www.youtube.com/watch?v=jw53YPDzqWA
So stop the exposure as soon the sun rises.
There is one simple rule: what hurts your eyes hurts your sensor, too.
Think of a lens like of a burning glass. If you have a big enough lens, then you can even burn paper with plain moonlight.
images containing bright stars will be overexposed and leave ghost images that are visible on subsequent images taken by the telescope. In a shared telescope, we cannot allow that to happen.
Text from an observatory in California.