Eyepieces, Barlows and diagonals - reducing internal reflections

[Mr Spock]

I've noticed quite a few components, despite having black interiors, reflect quite a bit of light. So I've bought some of that (expensive) non reflective black paint to try and reduce reflections as much as possible. I'm doing the insides of the tubes I use for Barlows and eyepiece barrels to start. I'll then be taking the lenses out of my Barlow nose piece to do that; I'll also be dismantling my diagonal to give that the same treatment.

I've only done one coat so far, and missed a few bits, but the difference is still remarkable. I did the inside of one of my Svbony 70mm tubes I use with a Meade 140 apo nose piece to give x2.18; also the barrels of my orthos. I used the 9mm ortho with a painted and unpainted 70mm tube (I have two, plus a 56mm). The painted tube gave a much darker sky background making stars stand out more. I used Castor as the main test subject. It was much easier to pick out fainter stars with the painted tube, though the poor seeing conditions didn't help. The 9mm + 70mm Barlow is x173. 

I'm not going to do more tests in better conditions. I've seen enough already to show me it works and was worth the cash.

[Roy Challen]

You can see the difference just from you picture. What paint is that? Google lens brings up sake😂

[Alien 13]

Nice, have thought about getting some of that paint for the focus tube of my Mak. maybe it will then transform into a "Questar" 😀

I imagine that paint would be brilliant for camera lens hoods too.

 

Alan

Edited May 5, 2022 by Alien 13

[Mr Spock]

Google Musou black paint. It absorbs 99.4% of light. I got mine from Amazon.

[johninderby]

Just hope the paint doesn’t flake off.

[Captain Scarlet]

Christ you said expensive but I wasn’t expecting that! £45 ish for 100ml. But I’m still tempted.

M

[Carbon Brush]

Thanks for posting. Was it OK going over existing paint? Just a small brush? Noting the seller recommends airbrush for best results.
At £450/litre I don't want to waste a drop learning the best application methods!

[Mr Spock]

Ordinary brush is fine. It only needs a thin coat though.

[Louis D]

11 hours ago, Alien 13 said:

Nice, have thought about getting some of that paint for the focus tube of my Mak.

I'm thinking of using some Protostar flocking material to line the rear baffle tube of my 127 Mak.  I just haven't had the time to work on that project.

[Alien 13]

1 minute ago, Louis D said:

I'm thinking of using some Protostar flocking material to line the rear baffle tube of my 127 Mak.  I just haven't had the time to work on that project.

Thanks, I did mean the baffle tube but there is not a lot of room in there so its either the flocking material or maybe a rolled cylinder made from a cut up bear can painted with the special paint stuff.

Alan

[Mr Spock]

My 12" needs flocking. It won't get to see this paint, not at those prices. The paint would cost as much as the scope!

[Alien 13]

10 minutes ago, Mr Spock said:

My 12" needs flocking. It won't get to see this paint, not at those prices. The paint would cost as much as the scope!

I am sure some critical items like the spider vanes and the focusser tube could be done.

Alan

[Ricochet]

That's a great change. Now I've seen the difference I'm sure I'll start spotting things that could do with being a darker black. 

[Don Pensack]

Flocking will make a huge difference:

https://www.cloudynights.com/topic/523747-deadening-a-6-f5-newtonian/?p=6993629

 

[Paz]

On 05/05/2022 at 09:33, johninderby said:

Just hope the paint doesn’t flake off.

This looks good but I do wonder about how well it lasts and how resistant it is to being disturbed / chipped / worn off. I am tempted to get some and test it out. It sounds expensive for some paint but it's not expensive in the context of astronomy stuff, and probably especially not for those of us who are always looking for improvements.

[Mr Spock]

It's not for hard wearing areas. For the insides of tubes it's going to be fine. 

From the bottle I have, I've barely used any. Given the substantial improvement it's made, it's good value for money.

[PeterStudz]

2 hours ago, Paz said:

This looks good but I do wonder about how well it lasts and how resistant it is to being disturbed / chipped / worn off. I am tempted to get some and test it out. It sounds expensive for some paint but it's not expensive in the context of astronomy stuff, and probably especially not for those of us who are always looking for improvements.

That’s what I’d be interested in. I tried some of that Black 3.0 - the blackest black black in the western universe - and I wasn’t impressed. With the test sections of plastic, aluminium, glass & steel that I tried it would flake off if you sneezed, especially on glass & metal. It went straight in the bin. Fortunately I’d only purchased a small sample bottle.

I then went back to blackboard paint. The adhesion on that was good and it’s black enough, or far blacker than what I was painting. 

Edited May 6, 2022 by PeterStudz

[PeterCPC]

Another alternative. I used some stove paint. I saw how flat it was when I sprayed a previous fire grate. I have used it to spray inside a barlow lens and looks good. Quite cheap too. 🙂

[Carbon Brush]

Wandering slightly off topic perhaps.

Some of our eyepieces, barlows, etc. are the £1.99p quality that came with the £50 scope.
Others have 3 figure price tags.

I would expect the quality stuff to already be made as black as black can be.

But across the (less than eye watering price) range, from the posts above, I get the impression that there are easy improvements to be made at low cost.
Do the low cost manufacturers really put in the effort?
Taking Celestron and Skywatcher as examples. They make (or have made for them) parts for low cost and premium scopes.
Compare the 10mm stock eyepiece provided with a cheap scope to what you expect to use with an ED80 or Esprit.
The cost difference is principally the glass. The cost of a couple of mL of paint for an eyepiece is surely negligible - at the wholesale price.
Is it too much ask the manufacturer to use decent paint over all of his product range?

Alternatively. Are we seeing the results of scope brand owners sub contracting the work and not watching quality?
I have seen paint flaking from inside finders (retail £50/£60 types) for no good reason.
I am not the only person who thinks the inside of the 'average' Skywatcher or similar newt is dark grey rather than black.

I appreciate that painting or flocking an OTA is far more effort and cost than for an eyepiece. I'm only thinking here about small parts.

Anyway. I'm sold on the £450/litre stuff for small areas. Maybe something more affordable for larger areas.
 

[Alien 13]

Slightly off topic I noticed that you can also get "whitest white" and "mirror" paint, the white reflects 99.9% of visable light so could be handy for painting tripod feet etc so you dont trip over them in the dark..

Alan

Edited May 7, 2022 by Alien 13

[Ricochet]

2 hours ago, Carbon Brush said:

Compare the 10mm stock eyepiece provided with a cheap scope to what you expect to use with an ED80 or Esprit

I've just bought a 72ED and the inside of that is what I would consider a dark grey like you describe their Newtonian insides. In fact I've just been inspired to dig through my astronomy drawer for the small piece of flocking left over from when I did my (Bresser) dob. The inside of the OTA could do with some attention too but I'll have to figure out how the lens cell comes off first. However, if they are going to scrimp somewhere I guess it is better that they scrimp on something I can fix rather than the quality of the optics, which so far seem very good. 

The inside of the dew shield showing the difference between the flocked area and the original paint (hidden under the lens cell when the dew shield is screwed back on). 

[jetstream]

This works.

 

[Louis D]

10 hours ago, jetstream said:

This works.

 

I've used it before for DIY projects.  While it's better than nothing, it's doesn't really have any light trap effect at grazing angles.

[bomberbaz]

Very interesting thread. I will have to dig out all my items that may benefit from a light coating to see if it is worthwhile. 

After that is my fishing tackle and box get their pre summer season tidy and clean.

Pfft, too many hobbies!

[v4cascade]

Did this to all my collimation EPs as well especially that tiny hole on the reflective angled piece that you look through. One was a cheap hollowed plastic and the other was a solid block of aluminum. Just let me say the drill bit they used to drill that hole was extremely worn. The tooling marks on the inside of that hole was ridiculously bad. The black paint covered up all those flaws although I'm not sure how much of an improvement it had but I'd like to think that it did.