Blackout paint

[Jonk]

I'm looking at the options, had anyone tried this or similar?  http://www.uvgear.co.uk/product/product315.htm

It's stage paint for blacking out areas that have UV lighting so appears to be ideal.

I've read that blackboard paint is ok too, but appears a lot cheaper, so I'm thinking is is water based?

[cosmojaydee]

Blackboard paint is Ideal for this and its not water based, if you want to spray paint then have a look at BBQ paint , I used this to spray paint my exhaust pipes on an old bike , its a mat finish also and all weather proof

[JamesF]

I recall some time back Olly (I think) posting some information suggesting that some types of black paint are quite reflective in near IR whereas others aren't.  Allegedly the paint used for barbeques and suchlike is supposed to have low reflectivity for near IR, so that's what I use.

James

[Jonk]

Ok cool - I'll look up BBQ paint.

What about log burner spray paint, same thing?

[Jonk]

AEROGLAZE Z306 FLAT BLACK appears to be the business, if I can find some.

[lensman57]

I recall some time back Olly (I think) posting some information suggesting that some types of black paint are quite reflective in near IR whereas others aren't.  Allegedly the paint used for barbeques and suchlike is supposed to have low reflectivity for near IR, so that's what I use.

James

I have read that even anodised Aluminium though none reflective in the visible spectrum is reflective in IR up to 90%. so much for our black extension tubes and so on.

A.G

[Mr Spock]

I find a lot of these paints can be quite reflective at low angles of incidence.

[lensman57]

I find a lot of these paints can be quite reflective at low angles of incidence.

That is my understanding too. There are some true light absorbing paper available in the US with an almost negligible reflectance but the price is anything but negligible. I have also heard that blackboard paint can be mixed with  very fine flour for a very effective anti reflective effect, I guess the fine flour particles act as a light  trap not unlike a stealth paint.

A.G

[AndyH]

Someone, somewhere, recommended this stuff. Possibly a member here on SGL?

http://www.astrogeraete.de/Antireflexfarbe.html

[PeterW]

Flock paper is good below 700nm. There re good paints, but they can be hard to obtain. E.g Mankiewicz Nextel Velvet-Coating 811-21. Otherwise krylon matt black seems to be used by some... Maybe put on more layers to get it rougher to see if it makes any difference to glancing incidence light.

A decent matt black spray paint should work. You might need to try adding baffles to stop reflections and scatter getting too far up the tube.

Cheers

PEterW

[Jonk]

I've had a quick look for baffle ideas - what have people fitted to their SW 150Ps (or 200s / 250s etc.)?

I also read that mixing some sand into the paint can help as a diffuser.

The reason I want some paint is for the spider viens and round the aperture, as it's all a bit too shiny for me - the OTA and focuser are flocked.

[Fred_76]

Hi

I wouldn't black paint the spider vanes. Black colour pumps calories out and the vanes will cool down below ambient temperature very quickly. Not only will it also cool you secondary mirror cell and accelerate apparition of dew, but also this temperature difference will induce a laminar air flow hence increase the apparent thickness of the vane.

The best solution for the vanes is a very reflective coating such as polished inox steel. If you look at "high end" reflectors, you will see that there design is like that.

Fred

[lensman57]

Hi

I wouldn't black paint the spider vanes. Black colour pumps calories out and the vanes will cool down below ambient temperature very quickly. Not only will it also cool you secondary mirror cell and accelerate apparition of dew, but also this temperature difference will induce a laminar air flow hence increase the apparent thickness of the vane.

The best solution for the vanes is a very reflective coating such as polished inox steel. If you look at "high end" reflectors, you will see that there design is like that.

Fred

That is interesting, do you have a link to a photo of these scopes please?

A.G

[JamesF]

Black colour pumps calories out and the vanes will cool down below ambient temperature very quickly.

Do you have any references for this?  It seems somewhat counter-intuitive, not to mention that different black coatings and paints have significantly varying emissivity across the IR and visible spectrum, so it might be interesting to get a better understanding of what is going on.

James

[Jonk]

Interesting - I'd like to see something on that too.

I've bought some stove paint for now.

[Calypsob]

Chalkboard paint is latex I think, its more matte than 4 other paints I tried. If you have a modded camera throw on an ir pass filter and check for reflectivity. I can tell you that anodized black aluminum reflects ir light 100% and the chalkboard paint reflected none.