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Paint coating inside spacers and extension rings

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#1 unimatrix0

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Posted 20 June 2021 - 11:39 PM

When I look at the inside of the spacer rings and parts, they are black inside, but it's shiny black. 

As far as my understanding goes, the last thing we want is the light to bounce around the imaging train so it's a reason why even the cheapest telescopes have flat /matte black finish with baffles, to minimize light reflection. 

On the other hand, most of these spacer rings and extensions are shiny and they are the closest to the sensor. 

Wouldn't it make sense to buy a flat black paint and lightly spray inside of them, to cut any chance for the light to cause weird effects ? 

Or, has anyone done anything similar or is this something too insignificant and it'd be a waste of time for little benefit? 



#2 astrokeith

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Posted 21 June 2021 - 02:19 AM

Good point.

 

In theory , at the back of a well built OTA, there shouldn't be any light hitting these surfaces so as to bounce off them. All light should be in the light cone converging on the eyepiece or sensor.

 

Stray light from filter slide mechanisms etc would be reflected.

 

It isnt easy to get a good flat black surface, especially at low angles of incidence. Ordinary matt paint would help a bit, but not completely. There are special paints, but they tend to be porous and have a habit of creating flakes. Especially a risk near edges and threads.

 

So unless you have a problem, dont worry would be my advice!



#3 unimatrix0

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Posted 21 June 2021 - 09:39 AM

Good point.

 

In theory , at the back of a well built OTA, there shouldn't be any light hitting these surfaces so as to bounce off them. All light should be in the light cone converging on the eyepiece or sensor.

 

Stray light from filter slide mechanisms etc would be reflected.

 

It isnt easy to get a good flat black surface, especially at low angles of incidence. Ordinary matt paint would help a bit, but not completely. There are special paints, but they tend to be porous and have a habit of creating flakes. Especially a risk near edges and threads.

 

So unless you have a problem, dont worry would be my advice!

Good point on the flaking. Possibly the risk of having those paint flakes falling on the sensor is worse than trying to stop something that may not cause any issues. 



#4 calypsob

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Posted 21 June 2021 - 09:48 AM

Ive only had issues with flaking if paint gets on the threads.
My favorite tools for spacer darkening are a Testors ultra flat black enamel pen and also I have a roll of black flocking adhesive used to make a border on a wall projected theatre screen. The adhesive is good for ota tubes and the pen is good for small stuff.


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