# will 50 minits of exposure shooting star trails pics brake my camera



## dub-sport (Feb 16, 2008)

hi there im quite new to all this any way iv brought the canon eos 350d dslr and im taking about 50 minit exposure   pics of the stars this is in the south of england im taking these pics late at night so it aint worm thats for sure i got told its the heat that brakes the camera and basicly is this true long exposure shortens the camera life very quickly i use my camera every Sunday thats about it really and now and then on family and sunsets an thats it if this is true how long do u think it will last .....any info on this will be great and im sorry for and spelling ..thanks


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## MichaelT (Feb 17, 2008)

I'm no expert at astronomical photography, but most digital camera's designed for that application have coolers to keep their CCD's stabilized.  If your camera has a CMOS sensor, they run at a lot less power, so you might be safer.

Maybe someone else has more information for you.


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## dub-sport (Feb 17, 2008)

thanks for your reply Michael T


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## Bill Boehme (Feb 17, 2008)

You can leave the shutter open for as long as you wish ... it won't hurt the camera, but make sure that the battery is charged so that it doesn't go dead in the middle of an exposure.


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## kundalini (Feb 17, 2008)

Sorry Bill Boehme, but your twelve exposures have nothing to do with the OP's original question. I'm guessing that each of those 12 exposures is no longer the 1/100th to 1/160th second. Much longer than 1/100, you will start to get blurs as the moon orbits.

As an example this one exposure was taken at shutter speed 1/160:








Long...really long exposures can possibly have a detrimental effect on the image with a cropped sensor. I can't remember the thread, but have a search within the last 3 months from a poster called Garbz with regard to long exposure. Best of my recollection is that it is possible to fry pixels, but there is more to it as far as image quality.


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## Sideburns (Feb 18, 2008)

the image quality will degrade so quickly, you'll probably never try to do it again.


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## Garbz (Feb 18, 2008)

The problem is heat which causes 3 issues.

1. Heat "kills" pixels. Some are more sensitive to this than others. Anything from shooting about 1/2 second upwards can drop out one or two pixels. It's the same ones each time. This is not dangerous and the pixels will be fine again next shot. But after 90 minutes you can expect a significant percentage of pixels to be stuck giving you an image literally full of red green and blue specs.

2. Heat causes a colour shift in pixels. After about 15-30 minutes this colour shift presents itself as a pink glow starting at the edge of the frame and moving inwards, and it builds up over time. At this point the camera should become noticeably warm. Again this is not damaging.

3. Finally sensors are not designed with heat in mind. Eventually if you're not lucky the sensor will cook itself. This depends on the individual sensor's failure, but the damage is permanent so I suggest you do NOT try and find out how far you can push it.

Given that film exhibits none of these problems this is a perfect excuse to grab your old film SLR out of the closet or grab one of eBay. The cost is not that much and you will get usable shots rather than noisy pink garbage.


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## Bill Boehme (Feb 18, 2008)

kundalini said:


> Long...really long exposures can possibly have a detrimental effect on the image with a cropped sensor. I can't remember the thread, but have a search within the last 3 months from a poster called Garbz with regard to long exposure. Best of my recollection is that it is possible to fry pixels, but there is more to it as far as image quality.



Overheating sensor elements (not pixels, which are image file elements) is an old technicians tale.  What will happen with really long exposures and extremely low light levels is that semiconductor thermal noise becomes the more significant contribution component of sensor output than actual light detection and the result is that the image will be very noisy, but it has nothing to do with sensor heating, per se.  The noise factor is actually an issue of the ambient temperature and is noticeable on long exposures only because the noise component has had time to integrate to a much greater level than it would otherwise.  Some specialized imaging sensors used in astronomical observation use cooling (sometimes even cryogenic cooling for highly specialized sensors), but the purpose is not to keep the sensor from getting hot -- it is to reduce electronic noise which is a function of temperature.

You are correct in your observation that the moon exposures were short, but the point of mentioning stacking had to do with noise reduction which will be a significant problem when weak light signals result in images with a poor S/S+N ratio.  Your assumption of blur on a longer moon exposure than about 0.01 seconds assumes that a lunar rate tracking system is not being used.  With my camera piggybacked onto my telescope drive, that is a non-issue.

Now, if you were to point the camera towards something really hot like the sun for a long exposure ... there would be some genuine heating -- the difference is that would be heat from an external source.  There is no significant internal heat generated in CMOS sensors.


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## dub-sport (Feb 18, 2008)

thanks for all your info its helped out alot Garbz i do seem to be getting little red and blue dots is it possible to get this sorted and how much would it cost to get my sensor cleaned in GBP i aint got the balls to do it my self  and when i take long exposures pics of the stars i seem to be getting a dark red ish back ground is this were there is lights around ? ........thanks peeps:thumbup::thumbup:


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## Bill Boehme (Feb 18, 2008)

dub-sport said:


> thanks for all your info its helped out alot Garbz i do seem to be getting little red and blue dots is it possible to get this sorted and how much would it cost to get my sensor cleaned in GBP i aint got the balls to do it my self  and when i take long exposures pics of the stars i seem to be getting a dark red ish back ground is this were there is lights around ? ........thanks peeps:thumbup::thumbup:



If you have dust on the sensor, it will show up as very large (and usually faint) fuzzy blobs.  The dots that you see do not sound like contamination on the sensor -- it sounds much more like it is just noise.  That can be minimized by using the shortest practical exposure time coupled with the largest aperture that your lens can provide.

In the US, the cost of having a camera's sensor cleaned is typically around $50.  Cleaning it yourself is quite easy and the first thing to try is very simple and safe -- just use a bulb type blower -- not the tiny cheap kind that comes with lens tissue as part of a $5 kit, but something comparable to a Rocket Blower.  That takes care of the dust bunnies in the majority of situations.  The next step is to use a wet cleaning method -- my favorite is #2 Sensor Swabs and Eclipse E2 fluid from Photographic Solutions.  Like most people, I was very nervous about trying that the first time, but I found that it was very simple and easy to do.  For anyone lacking manual dexterity, it might be best to pay a shop to do the job.

The dark reddish background is simply sky glow caused by light pollution.  The UK isn't known for having dark skies and so you can expect to have lots of glow in the sky.  Since your camera is mounted on a fixed tripod, image stacking is not an option, but if you had a tracking system to counteract the earth's rotation, you would be able to benefit from stacking programs to process multiple exposures into a single merged image.


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## dub-sport (Feb 19, 2008)

thank you for that im thinking of cleaning it i think its just were i dont want to c_ck it up that tho mate u have been a great help :thumbup::thumbup:


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## brileyphotog (Feb 24, 2008)

I'm still wondering what kind of results you're getting with 50 minute exposures due to the blur problem, as someone mentioned before.


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## Garbz (Feb 25, 2008)

Bill Boehme said:


> There is no significant internal heat generated in CMOS sensors.



Take a 50min exposure and then feel the back of your camera. It's not as bad as the heat generated by a CCD but that statement is utter hogwash.


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