Best black paint for inner tube

[Adaaam75]

Fellow Stargazers,

I have very bravely and carefully cleaned the corrector lens, primary and secondary mirrors of my C9.25 SCT today after extensive research (and NO washing up liquid!!!) and when I removed the lens I noticed some pitting in the black paint within the inside of the tube. I imagine this was caused by moisture in the tube however there is no other damage other than the paint itself. It is quite extensive though throughout the tube and caused some of the tiny black paint particles to fall off when touched.

I'd like to resolve this by prepping and painting the inside of the tube and wondered if there is a go to paint? Some quick research recommends Sennelier Mars Black however this dries to a satin finish and I imagine the preferred finish is Matt for less reflection.

I invite your thoughts on this and the best type and brand of paint for the job.

Clear Skies.

[astronymonkey]

Have you thought about flocking the inside of the tube rather than paint ?

I'd do that on a Newtonian but I'm sure others.will be able to say if should be done on an SCT.

Cheers

[RT65CB-SWL]

Vantablack... before you rush out and buy a can... win the lottery. It's not cheap.... 🤑🤣

[bottletopburly]

Or black3.0  absorbs 99.% of visible light even blacker than  vanta not sure how far 150ml will cover , black 2.0 available too 

https://culturehustle.com/products/black-3-0-the-worlds-blackest-black-acrylic-paint-150ml

[PeterStudz]

I tried Black3.0 but found that it would not adhere to metal (or plastics & glass for that matter) and would flake off at the slightest opportunity. Personally I would not allow it anywhere near optics. 

In the end I flocked and used blackboard paint for small areas and back/sides of the secondary. At least blackboard paint had good adhesion. 

Edited January 12, 2023 by PeterStudz

[Ratlet]

I'd look at flocking the inside rather than painting.  I did paint some parts of my 130pds (focuser tube and mirror edges) and just used some generic blackboard paint.  Very dark and Matt finish.

To make life easier I got a plastic poster cover ( https://www.ebay.co.uk/itm/261693313857?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=EKBTSg_tQPW&sssrc=2349624&ssuid=PvuSuZhdTlO&var=&widget_ver=artemis&media=COPY ) and cut this to fit the tube.  The spring in the plastic will force it onto the tube walls.

I then cut the flocking to fit the plastic poster tube and stuck that it.  Darker than a polar bear's nose at night.

[AstroKeith]

If it's flaking you are absolutely right to stabilise it. Else flakes on the optics!

The light it needs to absorb is mostly coming in at a grazing angle. Many so called black paints are almost shiny at these angles. The really black surfaces include a texture, even if it's too small to see. black3.0 is good.

The tube is I believe aluminium, therefore needs a special primer (acid etch).

Flocking can be effective, but can also hold moisture. So depends on where you will be storing the scope.

[Craney]

I'm not fully convinced that  Black3.0 is  the best out there..... as some advertising would promote.

I tried to darken a dew-shield that had seen better days with an undercoat of Black (v1) then a topcoat of Black3.0.

Start

During

end

It dries to a matt finish, but it does have a dull sheen to it.  That is,  it looks darker when wet.     The Black(v1) undercoat was not enough by itself.

It improved my dew-shield (slightly)  but   maybe flocking paper and blackboard paint may have been cheaper in the end.

Hope this helps.

Sean.

Edited January 12, 2023 by Craney

[drjolo]

I did a small test some time ago, and that is very true that at a grazing angle many black paints shines like crazy diamond.

Looking at 90 degrees

at 45 degrees

at 15 degrees

The numbers are mean level read with sampler.

Starting from the left there are:

• flock (velor)
• bottom: black acrylic mat paint with talcum powder, top: the same plus black mat spray (Boll)
• bottom: black acrylic mat paint without talcum, top: the same plus black mat spray (Boll)
• black mat spray plus talcum powder
• black mat spray
• nothing (aluminium) 

[AstroKeith]

25 minutes ago, drjolo said:

I did a small test some time ago, and that is very true that at a grazing angle many black paints shines like crazy diamond.

Looking at 90 degrees

 

at 45 degrees

 

at 15 degrees

 

The numbers are mean level read with sampler.

Starting from the left there are:

• flock (velor)
• bottom: black acrylic mat paint with talcum powder, top: the same plus black mat spray (Boll)
• bottom: black acrylic mat paint without talcum, top: the same plus black mat spray (Boll)
• black mat spray plus talcum powder
• black mat spray
• nothing (aluminium) 

Good examples! Shows that texture is very important.

When I worked in the optical industry we used Nextel velvet paint. Trouble is its about £500 a tin! They do a suede for the more commercial market which is much cheaper.

[doublevodka]

https://www.amazon.co.uk/Musou-Black-Water-based-Acrylic-Paint/dp/B08QSFNKYG is allegedly supposed to be good although I've not used it

Because I do everything on a budget I've used this stuff for "flocking" https://www.amazon.co.uk/BENECREAT-Adhesive-Self-Adhesive-Resistant-Multi-purpose/dp/B07BGZ82XH?pd_rd_w=P3GYq&content-id=amzn1.sym.e9c30756-181a-4068-ac3a-74afd7f110a2&pf_rd_p=e9c30756-181a-4068-ac3a-74afd7f110a2&pf_rd_r=FE419QEVEJC7JBKSE887&pd_rd_wg=TAqKe&pd_rd_r=1f96cefe-6995-44ce-9269-e04ba776fe7f&pd_rd_i=B07BGZ82XH&psc=1&ref_=pd_bap_d_grid_rp_0_21_t  whilst it's not as good  as proper astro flocking material it does a better job than the paint that's been in my scopes

FLO have a couple of options too - https://www.firstlightoptics.com/telescope-flocking-material.html - Protostar is supposed to be very good

[Ricochet]

I used a combination of Musou and flocking on my 72ED, there is a thread somewhere with photos in. I found that brushing the Musou straight onto the tube didn't leave a great looking finish and was still reasonably shiny under bright light at shallow angles. I think that spraying it if you have the tools and skill is likely to give a much better finish. I also tried painting it onto flocking and this actually gave the best result and improved the flocking at shallow angles. It does make the flocking hard so I think I only did this on the inside of the scope and left the flocking as it is in the dew shield where it is more likely to get knocked. I think that with either Musou or black 3.0 the key would be to undercoat with a textured paint and then just use the expensive paint as a top coat. 

[Adaaam75]

5 hours ago, Ratlet said:

I'd look at flocking the inside rather than painting.  I did paint some parts of my 130pds (focuser tube and mirror edges) and just used some generic blackboard paint.  Very dark and Matt finish.

To make life easier I got a plastic poster cover ( https://www.ebay.co.uk/itm/261693313857?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=EKBTSg_tQPW&sssrc=2349624&ssuid=PvuSuZhdTlO&var=&widget_ver=artemis&media=COPY ) and cut this to fit the tube.  The spring in the plastic will force it onto the tube walls.

I then cut the flocking to fit the plastic poster tube and stuck that it.  Darker than a polar bear's nose at night.

That's great advice thanks mate, I'll look into it 👍🏼

[ONIKKINEN]

+1 vote for flocking.

This stuff is much darker at an angle than Black 2.0: https://www.firstlightoptics.com/telescope-flocking-material/black-velour-telescope-flocking-material.html

Cheap and easy to apply, highly recommended. The adhesive is strong once you rub it in place and let it be for a while, but you can peel it off and reapply it if you make a mess or leave bubbles and want to reapply. It also sticks to itself so you can eyeball the cut and have it overlap.

[bottletopburly]

I believe there is a flocking material that blocks 99%  of light too , expensive though , I see if I can find it .

[PeterStudz]

26 minutes ago, bottletopburly said:

I believe there is a flocking material that blocks 99%  of light too , expensive though , I see if I can find it .

I think you talking about Protostar flocking material. But it’s not the cheapest!

https://www.firstlightoptics.com/telescope-flocking-material.html

[great_bear]

On 12/01/2023 at 11:23, Ricochet said:

I found that brushing the Musou straight onto the tube didn't leave a great looking finish and was still reasonably shiny under bright light at shallow angles.

Yes, I did the same with the baffle tube of my Mak 180.

It offered no improvement at all over the Sky-Watcher factory finish (although it wasn't any worse, either). Musou clearly offers no benefit at oblique angles although may be of some use when painted onto small parts which are too fiddly to be flocked.

[Adaaam75]

I bought the flocking from FLO after some excellent customer service and advice as they sent my photos of the tube to Celestron U.S. and got good feedback however Celestron predictably advised against after market upgrades!.

FLO advised 2 rolls of flocking based on the surface area of my Celestron 9.25 SCT and that flocking cost £20 Inc postage however I had a full roll left over so that will be going in my second scope.

The flocking adds such a smooth dark finish that hardly any paint could match especially at that price and was very easy to apply with some confidence of removing the lens and mirror (they got a clean too) in comparison to painting.

Now I don't have to worry about any more internal issues and although the scope will need a little more cooling down time, it's a very Matt dark black inside! 😎

[Louis D]

Did you flock the interior of each baffle tube as well?  That's where I'm getting most of my internal reflections in my 127 Mak.

[Adaaam75]

I removed the corrector lens and the primary mirror housing on the Celestron SCT so I was just left with a metal tube which made it easy to line. The Skywatcher 130 reflector was a little harder as it's longer and narrower but after removing the mirror and secondary mirror it was simple enough.

A quick collimation later and both sorted 👍🏼