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Newb - just started with "black spots" question

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#1 rj144

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Posted 31 October 2020 - 03:17 PM

Hello.  This is my first post/thread.  I literally just started last week. 

 

Now this might seem like an obvious question to answer, but I can't can't seem to figure the whole thing out.  I am using a Celestron 6se and an adapter for a camera.  I first tested this with a Sony NEX 3 (an older camera) that's APSC, here is the result:

 

https://youtu.be/RkURrALT_bg

 

See those black spots all over the place.  So, I cleaned every optical piece to get rid of them:  the eyepieces, the right angle adapter, the adapter to the camera, blew out sensor dust, and even the front of the telescope.  Didn't really help much (after doing all that the spots were as present as before), but then I changed to my a7iii and this is the result:

 

https://youtu.be/_sl5fF7gH5M

 

It is much better, but there are still some small spots  if you look closely (look in the corners when that area passes over the brighter areas) and it annoys me.  It's not sensor dust either.  I've taken videos of white fully exposed walls and don't see any dust at all (actually on either camera).  I also can't figure out why changing cameras would make that much of a difference as both don't have dust.

 

So, does anyone have any experience with this and maybe knows what to pinpoint.  Like I said, I really have cleaned everything possible.

 

Thanks.


Edited by rj144, 31 October 2020 - 03:18 PM.


#2 sg6

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Posted 31 October 2020 - 03:28 PM

Can only see the first one, the second is classed as Private.

First thought is "dead pixels".

 

Basically they are dead and will never produce anything so appear black. They seem too small be be anywhere over then the sensor. Often occurs the other way where they are "hot pixels" and produce bright pixels all the time.

 

That is my guess anyway.

Not sure how many pixels on a Sony NEX3  but you cannot expect 100% or them to work.

 

Also No Astrophotography in this section and that is some form of imaging. Ask about a move to something like Solar System imaging, or whatever it is called now.


Edited by sg6, 31 October 2020 - 03:30 PM.

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#3 rj144

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Posted 31 October 2020 - 03:40 PM

Can only see the first one, the second is classed as Private.

First thought is "dead pixels".

 

Basically they are dead and will never produce anything so appear black. They seem too small be be anywhere over then the sensor. Often occurs the other way where they are "hot pixels" and produce bright pixels all the time.

 

That is my guess anyway.

Not sure how many pixels on a Sony NEX3  but you cannot expect 100% or them to work.

 

Also No Astrophotography in this section and that is some form of imaging. Ask about a move to something like Solar System imaging, or whatever it is called now.

 

Thanks for the reply.  It's not dead pixels though.  When I take a pic a video of a white wall with the same camera, no spots show up.

 

Also, the other video is now able to be viewed.  Sorry about that.



#4 Daveatvt01

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Posted 31 October 2020 - 03:57 PM

It’s most likely sensor dust.

Based on the vignetting in the white wall pics, I’d hazard a guess that your wall photo was not taken at f10 or slower. Try stopping your lens all the way down and see if the sensor dust shows up then. 
But since it is in focus (or almost in focus) it has to be on or right up against the sensor. 
 


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#5 rj144

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Posted 31 October 2020 - 04:02 PM

It’s most likely sensor dust.

Based on the vignetting in the white wall pics, I’d hazard a guess that your wall photo was not taken at f10 or slower. Try stopping your lens all the way down and see if the sensor dust shows up then. 
But since it is in focus (or almost in focus) it has to be on or right up against the sensor. 
 

You know, I'm usually pretty good with cameras, but I normally shoot wide open and I always forget sensor dust isn't resolved wide open.  I should have known that, but this is why I posted here. It is mostly sensor dust.

 

Thanks!



#6 Daveatvt01

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Posted 31 October 2020 - 08:22 PM

Glad you got it sorted out, welcome to the forum!




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