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How to know if mirror/shutter is failing and how?

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#1 StarBurger

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Posted 26 September 2020 - 03:37 PM

Try as I might I cannot find a way of knowing what my shutter count is. I have a Canon XS and a 3 Ti and in spite of posts telling me how, none seem to work for me.

I ask this as I am suddenly seeing much more debris arriving on my sensor with the XS even in a closed OTA train.

The arriving "rocks" are more than just dust motes.

Is there a typical way in which the mirror/shutter mechanisms fail? Am I seeing a deterioration in any "soft" components, e.g. flaking rubber/non-metal part/trims?



#2 otoien

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Posted 26 September 2020 - 03:59 PM

Try ExifTools (I prefer to operate it with EXIFToolGUI), and look in the maker notes. However time to shutter failure can vary widely from the nominal shutter life, so a record of shutter actuations might not be a too useful metrics to predict shutter failure. If source of debris is crumbling foam I would think that to be more of an aging phenomenon. Also look into the optical train as a source of debris (not sure what "closed OTA train" implies).


Edited by otoien, 26 September 2020 - 03:59 PM.


#3 StarBurger

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Posted 26 September 2020 - 04:34 PM

By "closed" I mean the camera stays attached to the focuser so in theory nothing should enter the OTA column.

I have looked hard and the OTA train contains nothing I suspect could generate large particles. 

At one time I supported the OTA and optical train inverted while I ran an electrical massager up and down to vibrate possible debris out of the OTA. Nothing fell out onto a white tissue.

I am realistic enough not to believe it's impossible! I just suspect that the likeliest source is the camera.

And it is an aging camera.

Does anyone know this camera (Canon XS) and know where to look if there is any organic deterioration?

This may appear a little OCD but random c**p is ruining long exposures.



#4 kathyastro

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Posted 26 September 2020 - 05:31 PM

I don't know that camera, but I know that some cameras have foam at the edges of the mirror to make a light-tight seal when the mirror is up.  It is likely synthetic rubber, which deteriorates over time.  Deteriorating foam rubber does get crumbly.



#5 nofxrx

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Posted 26 September 2020 - 05:35 PM

Shutter failure almost always presents itself as a partially exposed image, meaning part of the sensor is not exposing anything due to a shutter leaf still being in front of it. There will be a large black shaded portion of the image. You would clearly notice this and it would become more frequent as time goes on.
You should be able to get shutter count on those models using EOScount. It will cost you a dollar or two...
Don't worry about shutters until you see what i described above, then consider it to eventually become unusable. Shutter repairs (replacememts) are no easy feat and would probably not be cost effective for those old models. I have torn down / modified hundreds of cameras and replaced one shutter over the years. I will not bother trying again.

If you are seeing lots of dust in your images it's probably time to give the camera and sensor a good cleaning. Dust is a way of life with removable lens cameras. You can mitigate it as best you can with good clean practices but even then you WILL need to clean occasionally.

Good luck

#6 nofxrx

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Posted 26 September 2020 - 06:00 PM

Edit, this would be the symptom seen with standard daytime images where fractions of a second are used and a shutter leaf getting sticky or not moving at the right speed would be clearly visible.
For astro i honestly do not think you would ever really notice it, but maybe you would. I would think if you blink through your flat frames from each night you could see this issue since those would use much shorter exposure than your light frames.
Hope this all makes sense. Sorry i forgot which forum i was on when i first replied thinking it was general (normal) photography LOL


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