Jump to content

NLCbanner2024.jpg.2478be509670e60c2d6efd04834b8b47.jpg

Need to clean motes on CCD sensor

konstantinos75

Recommended Posts

konstantinos75

konstantinos75

Posted
Posted

Hello
 
I would like your expert opinion with a problem I have with my SBIG ST2000XM astronomical camera.
The camera has the CCD chip Kodak KAI-2020M +
 
My problem is that the CCD sensor is full of motes.
I have tried many times with a blower and a small brush to clean it but the motes still remain.
After blowing and using the brush I have noticed the motes change position but they still remain on the CCD sensor.
I am not sure if they are caused by dust or humidity on the sensor.
 
I send you an image I took with my camera to see the motes.
 
Could you recommend the best way to get rid of these motes?

I am asking this question because this is what I have done
 
Open the camera for the first time. Open the CCD sensor chamber. Use a blower to remove any dust from the surface.
Close the sensor chamber. Put back the filter wheel. Camera ready. Take a flat frame. The frame looks very good all clean.
 
Then after some time without opening the camera again, I noticed these motes on my flat frames. Could these motes be caused by the humidity entering the CCD sensor the first time? 
And for some reason the desicant has not absorbed the humidity or they are dust motes indeed which remain due to static electricity?

For your reference this is what SBIG recommends
https://www.sbig.com/site/assets/files/18147/cleaning_20ccds1.pdf
 
Thank you

flat.jpg

CCD sensor.jpg

Link to comment
Share on other sites
DHEB

DHEB

Posted
Posted

I have had marks like these in my DSLR. I guess they come from dew deposited on the sensor. I removed them by blocking the mirror and very gently sweeping the sensor with a cotton swap slightly wet with isopropyl. I understand this might sound heretic, but it actually solved the problem for me without any apparent damage. There are better options with special fluids and special brushes though. The usual caveat applies here: touching the sensor carelessly might damage it permanently, so this is nothing to be done on a daily basis, only when the marks have become a problem.

Link to comment
Share on other sites
ollypenrice

ollypenrice

Posted
Posted

Are you sure these are on the sensor? They look rather large and out of focus to me, suggesting they are made by dust further away. They also look transparent rather than solid and they all have a similar lighting effect in that they seem to be darkest in the lower left rim. Dust on the sensor usually makes a small, tight dark mark, jet black. Finally they are all remarkably round, which is what you'd expect from a small particle forward of the sensor. Could this be dust on the rear of the sensor window, possibly dust you blew loose inside the chamber? The more I look at the image the more convinced I am the dust is forward of the sensor.

Olly

 

Link to comment
Share on other sites
konstantinos75

konstantinos75

Posted
  • Author
Posted

Hi
 
Thank you for your reply. I got a hint that these dust motes are not on the sensor surface. If that was the case they would look focused and tiny dust motes in the flat frame.
 
They exist in the window glass which lies ontop of the sensor. 
 
So I will proceed to clean this window with isopropyl alcohol first. Then I will let you know my result.

Link to comment
Share on other sites
ollypenrice

ollypenrice

Posted
Posted

Much better to have them on the window than the sensor. It might be worth reading up on how to keep dust out when working in 'clean room' conditions. There are several things you can do to keep things clean but I don't know much about this. I do know there are rules to follow, though. It will all be on the net.

Olly

Link to comment
Share on other sites
konstantinos75

konstantinos75

Posted
  • Author
Posted

Hi
I will need to continue my experiments. I will use a micro fiber cloth and wet it with some isopropyl alcohol. Then wipe it gently on the sensor glass window both sides. Then same job with another micro fiber cloth on the ccd sensor chip. Then assemble the camera and place a new desiccant inside. Let it idle for a couple of days so that the desiccant absorbs all moisture in the ccd chamber. Then check again for motes. If the motes still appear I will take the camera to service.

Link to comment
Share on other sites
konstantinos75

konstantinos75

Posted
  • Author
Posted

Hi

I have good news this time!

I continued my experiments to clean the camera.
This time I used these glasses wipes from Lidl (cost 1,11 Euro)
https://www.pentaxuser.com/images/comment_pictures/20982/20982_1423777878.jpg
and a mobile phone monitor tissue.

Use W5 glasses wipes first then immediately the mobile phone monitor tissue to absorb the moisture.
I did this on the CCD sensor surface and on the glass window which covers the CCD sensor chamber.

Then I took flat frames with the camera connected to the FLAT BOX only and bingo!!! The flats look very good now the dirt has almost gone.
But as you can see there a few motes just a few. These dust motes are not on the CCD sensor surface but on the the glass window which covers the CCD sensor chamber. It's easy to see this because they are big and not focused..

See the camera flats here: https://www.dropbox.com/s/sq5gdb48i54elds/FLATS_camera.zip?dl=0

After that I connected the camera to my two telescopes one each time and took a flat frame.
Both telescopes show the same dust motes and in same position.

Vixen ED81s flat: https://www.dropbox.com/s/07h79ic9zmetzhj/FLAT-LUM-telescope-VixenEd81s.jpg?dl=0
Vixen VC200L flat: https://www.dropbox.com/s/dg9my8slmc7mabm/FLAT-LUM-telescope-VC200L.jpg?dl=0

My experiment proves that there are some dust motes on the the glass window which covers the CCD sensor chamber. I will need to repeat the cleaning only to this window.

Hopefully my problem will be completely solved after that :)

Link to comment
Share on other sites
konstantinos75

konstantinos75

Posted
  • Author
Posted

Hi

My assumption was wrong. The dust motes were not in the chamber glass window but on the surface of the CCD sensor.

I tried to clean again the CCD sensor and now almost all the dust motes are gone as you can see in the attached flat frame.

The flat frame was captured with the camera attached to my telescope Vixen ED81s.

Here's the latest flat frame: https://www.dropbox.com/s/e8cu002pybqkvmr/new-flat.jpg?dl=0

You can compare it with the old flat frame with this setup:  https://www.dropbox.com/s/07h79ic9zmetzhj/FLAT-LUM-telescope-VixenEd81s.jpg?dl=0

But unfortunately the sensor is scratched now in the top left corner you can see the black line.

I would like to ask you if this is a big problem or this scratch can be removed after calibration of my light frames with the master FLAT frame.

Thank you

 

 

Link to comment
Share on other sites
DHEB

DHEB

Posted
Posted

Are you sure that the streak is a scratch? I would say it is clean there. In any case, it is only the corner, so if you think it is clean overall it is probably better to leave it like this and not touch it anymore.

Link to comment
Share on other sites
DHEB

DHEB

Posted
Posted
33 minutes ago, konstantinos75 said:

Hi

I don't know if the streak is a scratch on the sensor surface or a fibre from the cleaning cloth I used which is stuck on the sensor.

More probably is the second option but I am not sure...

I don't really know, but I do not think it is a fibre either. If I were you I would leave it like this until further investigation and advice. Good luck.

Link to comment
Share on other sites
konstantinos75

konstantinos75

Posted
  • Author
Posted

Hi

I have measured the ADU value inside the area of the streak and as you can see it's about 31,000 ADU

This proves is not a scratch on the CCD sensor. Maybe the streak is a kind of salted substance on the surface of the CCD sensor.

This could explain why it always remain still despite the methods I have used to clean it (cotton swabs, microfiber tissue, blower).

If this is the case what is the most effective method to remove salted substances from the CCD sensor?

streak.JPG

Link to comment
Share on other sites
Dr_Ju_ju

Dr_Ju_ju

Posted
Posted

distilled, de-ionized, filtered water...

To me it looks like a smear caused by, for example, a cotton bud, that had been swiped down from left down right, lifting off towards the end....

 

Link to comment
Share on other sites
DHEB

DHEB

Posted
Posted
1 hour ago, konstantinos75 said:

Hi

Time now for more professional cleaning solutions. Hopefully the streak on the CCD sensor will be gone.

Otherwise I will have to live with it.

 

ccd-clean.jpg

Good luck!

Link to comment
Share on other sites
konstantinos75

konstantinos75

Posted
  • Author
Posted

Hi

The camera sensor was cleaned with above cleaning solution.

This is the latest flat frame with the camera attached to my refractor telescope: https://www.dropbox.com/home?preview=flat.jpg

Unfortunately the streak cannot be gone it is indeed a little scratch on the ccd sensor protective layer.

But the good news now.

This is a 20 min test light frame exposure: https://www.dropbox.com/home?preview=light-20min.jpg

This is the light frame calibrated only with the flat frame: https://www.dropbox.com/home?preview=light-20min---cal.jpg

Success the streak is gone also the dust motes and vignetting. Flat frame made its magic :)

Let's consider this topic as closed.

Thank you all for your support and understanding

Regards, Konstantinos

 

 

 

Link to comment
Share on other sites
neil phillips

neil phillips

Posted
Posted
On ‎5‎/‎25‎/‎2016 at 21:09, Dr_Ju_ju said:

distilled, de-ionized, filtered water...

To me it looks like a smear caused by, for example, a cotton bud, that had been swiped down from left down right, lifting off towards the end....

 

So is distilled water safe to use on a c moss sensor ?

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.