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Date: 24 Apr 2007 14:44:51
From: Peter Weld
Subject: Flat Black - where, what ??
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Has anyone found a flat black that will not burnish when touched
and handled?
In the midwest.
TIA
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Has anyone found a flat black that <u >will not burnish when touched</u>
<br ><u>and handled?</u><u></u>
<p >In the midwest.
<p >TIA
<br >
<br > </html>
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Date: 29 Apr 2007 23:51:16
From: Knap
Subject: Re: Flat Black - where, what ??
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thanks Martin.
Martin Brown wrote:
> On Apr 26, 6:10 am, Weldon <weld...@mchsi.com> wrote:
> > understand the principle however there used to be flat blacks
> > like that sold by Edmund that did not burnish - the same for
> > most parts from Perkin Elmer, Melles Griot, etc ... Takahashi ...
> > whatever it is they are using. Take a good eyepieve and rub the
> > inside of the barrel - doesnt burnish. Maybe I should ask TeleVue
> > or somebody like that ....
> > Thanks -
>
> You are really up against it. The oils from your skin will change the
> surface characteristics of a matt black paint. Sometimes making it
> look blacker and almost always making it look less matt. However, matt
> finish isn't everything as others have said what matters is how much
> stray light can get through to where it isn't wanted. Grooves and
> other surface modifications are often used to make paints appear
> blacker than black.
>
> Under some circumstances a gloss black can be more effectively "black"
> for all practical purposes than a flat matt black. You just have to
> ensure that the stray light from specular reflections ends up in a
> safe place. A fairly obvious example is in photographic papers where
> the contrast visible in glossy prints look significantly higher under
> most lighting conditions. The only exception is when specualar glare
> directkly affects line of sight.
>
> Regards,
> Martin Brown
>
> > Chris L Peterson wrote:
> > > On Tue, 24 Apr 2007 14:44:51 -0500, Peter Weld <h...@mchsi.com> wrote:
> >
> > > >Has anyone found a flat black that will not burnish when touched
> > > >and handled?
> >
> > > What you want may not exist. Flat black paint works in part by leaving a
> > > surface of randomly oriented particles or fibers. They are naturally
> > > fragile, and can easily be polished off by contact, or filled with skin
> > > oils.
> >
> > > Normally, if you want a surface to have low reflectivity you need to
> > > modify it mechanically- some sort of bead blasting, cutting fine
> > > grooves, etc. Then you apply the flat black paint. A prepared surface
> > > like that is much more resistant to contact.
> >
> > > _________________________________________________
> >
> > > Chris L Peterson
> > > Cloudbait Observatory
> > >http://www.cloudbait.com- Hide quoted text -
> >
> > - Show quoted text -
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Date:
From: Martin Brown
Subject: Re: Flat Black - where, what ??
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Date: 25 Apr 2007 22:38:16
From: Chris L Peterson
Subject: Re: Flat Black - where, what ??
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On Tue, 24 Apr 2007 14:44:51 -0500, Peter Weld <hmido@mchsi.com > wrote:
>Has anyone found a flat black that will not burnish when touched
>and handled?
What you want may not exist. Flat black paint works in part by leaving a
surface of randomly oriented particles or fibers. They are naturally
fragile, and can easily be polished off by contact, or filled with skin
oils.
Normally, if you want a surface to have low reflectivity you need to
modify it mechanically- some sort of bead blasting, cutting fine
grooves, etc. Then you apply the flat black paint. A prepared surface
like that is much more resistant to contact.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 26 Apr 2007 00:10:23
From: Weldon
Subject: Re: Flat Black - where, what ??
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understand the principle however there used to be flat blacks
like that sold by Edmund that did not burnish - the same for
most parts from Perkin Elmer, Melles Griot, etc ... Takahashi ...
whatever it is they are using. Take a good eyepieve and rub the
inside of the barrel - doesnt burnish. Maybe I should ask TeleVue
or somebody like that ....
Thanks -
Chris L Peterson wrote:
> On Tue, 24 Apr 2007 14:44:51 -0500, Peter Weld <hmido@mchsi.com> wrote:
>
> >Has anyone found a flat black that will not burnish when touched
> >and handled?
>
> What you want may not exist. Flat black paint works in part by leaving a
> surface of randomly oriented particles or fibers. They are naturally
> fragile, and can easily be polished off by contact, or filled with skin
> oils.
>
> Normally, if you want a surface to have low reflectivity you need to
> modify it mechanically- some sort of bead blasting, cutting fine
> grooves, etc. Then you apply the flat black paint. A prepared surface
> like that is much more resistant to contact.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
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Date: 26 Apr 2007 09:37:04
From: Dennis Woos
Subject: Re: Flat Black - where, what ??
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"Weldon" <weldpet@mchsi.com > wrote in message
news:4630343E.EA524902@mchsi.com...
> understand the principle however there used to be flat blacks
> like that sold by Edmund that did not burnish - the same for
> most parts from Perkin Elmer, Melles Griot, etc ... Takahashi ...
> whatever it is they are using. Take a good eyepieve and rub the
> inside of the barrel - doesnt burnish. Maybe I should ask TeleVue
> or somebody like that ....
> Thanks -
Please post back on what you find out. Thanks.
Dennis
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Date: 27 Apr 2007 01:25:29
From: Pete Weldon
Subject: Re: Flat Black - where, what ??
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I did find Starlord's $1 WalMart flat black - what a deal!
But Chris and Brian etc now say reflective black might be
better and the principle is simple once you think about it.
In fact my own experience tends to back them up now that
I think about it. (It must be age finding me finally).
But, I also made a discovery at Starlord's WalMart.
A Krylon Ultra Flat Black Non Reflective Camoflague paint
like deer hunters use..... and when you spray it is very diffuse.
But, Im going to go with Chris and Brian and WH Greer because
I think they are correct. And oddly enough now that I really think
about the trully black tubes Ive had in the past, I think a little
reflectivity is not a bad thing at all!
Thanks to all -
Pete
Dennis Woos wrote:
> "Weldon" <weldpet@mchsi.com> wrote in message
> news:4630343E.EA524902@mchsi.com...
> > understand the principle however there used to be flat blacks
> > like that sold by Edmund that did not burnish - the same for
> > most parts from Perkin Elmer, Melles Griot, etc ... Takahashi ...
> > whatever it is they are using. Take a good eyepieve and rub the
> > inside of the barrel - doesnt burnish. Maybe I should ask TeleVue
> > or somebody like that ....
> > Thanks -
>
> Please post back on what you find out. Thanks.
>
> Dennis
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Date: 25 Apr 2007 18:44:18
From: W. H. Greer
Subject: Re: Flat Black - where, what ??
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In many if not most places (in a telescope) glossy black can be
substituted for flat black with superior overall results when viewed
at the eyepiece or focuser.
--
Bill
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Date: 26 Apr 2007 00:11:00
From: Weldon
Subject: Re: Flat Black - where, what ??
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"W. H. Greer" wrote:
> In many if not most places (in a telescope) glossy black can be
> substituted for flat black with superior overall results
now that is a novel principle - care to explain?
Pete
> when viewed
> at the eyepiece or focuser.
> --
> Bill
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Date: 26 Apr 2007 08:42:58
From: W. H. Greer
Subject: Re: Flat Black - where, what ??
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Pete wrote:
>"W. H. Greer" wrote:
>
>> In many if not most places (in a telescope) glossy black can be
>> substituted for flat black with superior overall results
>
>now that is a novel principle - care to explain?
Brian provided a good and accurate explanation.
The key to the successful use of glossy black is a knowledge of all
the angles from which light may enter a system, knowing where you
don't want the light, and a working knowledge of the law of
reflection: "The angle of incidence equals the angle of reflection".
When utilized in an intelligent manner, glossy black is superior to
flat black for minimizing stray light. The stray light is effectively
directed away from where you don't want it; but flat black is safer
and a good alternative if one prefers to not think so much ;-)
--
Bill
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Date: 27 Apr 2007 01:19:10
From: Pete Weldon
Subject: Re: Flat Black - where, what ??
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"W. H. Greer" wrote:
> Pete wrote:
>
> >"W. H. Greer" wrote:
> >
> >> In many if not most places (in a telescope) glossy black can be
> >> substituted for flat black with superior overall results
> >
> >now that is a novel principle - care to explain?
>
> Brian provided a good and accurate explanation.
>
> The key to the successful use of glossy black is a knowledge of all
> the angles from which light may enter a system, knowing where you
> don't want the light, and a working knowledge of the law of
> reflection: "The angle of incidence equals the angle of reflection".
>
> When utilized in an intelligent manner, glossy black is superior to
> flat black for minimizing stray light. The stray light is effectively
> directed away from where you don't want it; but flat black is safer
> and a good alternative if one prefers to not think so much ;-)
> --
> Bill
I believe you and Brian and Chris are probably correct, now.
Chris brings up the point of mirrors even being used to redirect light in
some situations and he's absolutely correct.
Thank you -
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Date: 25 Apr 2007 22:55:38
From: Brian Tung
Subject: Re: Flat Black - where, what ??
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Bill Greer wrote:
> In many if not most places (in a telescope) glossy black can be
> substituted for flat black with superior overall results
Pete wrote:
> now that is a novel principle - care to explain?
I'm not Bill, but I'm guessing it's because glossy black reflects little
light (because it's black), and what it does reflect, goes in a very
particular direction, which most of the time is not toward the eyepiece.
Whereas with flat black, which reflects diffusely, light hitting any
place in the tube has some chance of making it into the eyepiece.
It's like if you look at a streetlight in a mirror. Most of the mirror
is not reflecting any light into your eye; it's only the small part of
the mirror where you see the streetlight's image that is directing any
of that light toward you. Whereas if a cement sidewalk is the thing
that's reflecting the light, any individual part of the sidewalk is
less bright than the one part of the mirror, but all parts of the
sidewalk reflect *some* light toward you.
--
Brian Tung <brian@isi.edu >
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 27 Apr 2007 01:15:08
From: Pete Weldon
Subject: Re: Flat Black - where, what ??
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Brian Tung wrote:
> Bill Greer wrote:
> > In many if not most places (in a telescope) glossy black can be
> > substituted for flat black with superior overall results
>
> Pete wrote:
> > now that is a novel principle - care to explain?
>
> I'm not Bill, but I'm guessing it's because glossy black reflects little
> light (because it's black), and what it does reflect, goes in a very
> particular direction, which most of the time is not toward the eyepiece.
> Whereas with flat black, which reflects diffusely, light hitting any
> place in the tube has some chance of making it into the eyepiece.
>
> It's like if you look at a streetlight in a mirror. Most of the mirror
> is not reflecting any light into your eye; it's only the small part of
> the mirror where you see the streetlight's image that is directing any
> of that light toward you. Whereas if a cement sidewalk is the thing
> that's reflecting the light, any individual part of the sidewalk is
> less bright than the one part of the mirror, but all parts of the
> sidewalk reflect *some* light toward you.
>
You may have something here. I could set up a small experiment and test it
one way or the other but your principle sounds good.
This is not a telescope tube but an optical chamber consisting of
mirrors, gratings, lenses, etc all in diverse places and some impossible to
shield without blocking optrical pathways. A
double pass dual grating monochromator (photometer) chamber !
I did find one paint today which might be worthwhile. It is the
Krylon Ultra Flat Black Camoflague paint. Said to be "diffuse and
nonreflective". Found it at WalMart when I was looking and found Starlord's
$1 flat black spray paint.
But I think you may have something here in the principle you cite.
Now that I think back, some of the darkest newtonian tubes I
ever had were in satin dense black.
Thanks!
Pete
>
> --
> Brian Tung <brian@isi.edu>
> The Astronomy Corner at http://astro.isi.edu/
> Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
> The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
> My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html
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Date: 26 Apr 2007 14:00:53
From: Chris L Peterson
Subject: Re: Flat Black - where, what ??
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On Wed, 25 Apr 2007 22:55:38 -0700 (PDT), brian@isi.edu (Brian Tung)
wrote:
>I'm not Bill, but I'm guessing it's because glossy black reflects little
>light (because it's black), and what it does reflect, goes in a very
>particular direction, which most of the time is not toward the eyepiece.
>Whereas with flat black, which reflects diffusely, light hitting any
>place in the tube has some chance of making it into the eyepiece.
It is common to use mirrors as baffles or stray light management tools
in many optical systems, because they are much more efficient at
redirecting unwanted light than the best absorbers.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 25 Apr 2007 18:22:00
From: starburst
Subject: Re: Flat Black - where, what ??
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Peter Weld wrote:
> Has anyone found a flat black that _will not burnish when touched_
> _and handled?___
>
> In the midwest.
>
> TIA
>
>
>
If it's that much of an issue, have you considered roughing the surface
before painting it? I've seen folks who have used all sorts of things,
like sawdust and shredded pvc, glued to the inside of the tube and then
hit with krylon flat black. Works really well.
'luck - Chris
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Date: 26 Apr 2007 00:06:55
From: Weldon
Subject: Re: Flat Black - where, what ??
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starburst wrote:
> Peter Weld wrote:
> > Has anyone found a flat black that _will not burnish when touched_
> > _and handled?___
> >
> > In the midwest.
> >
> > TIA
> >
> >
> >
>
> If it's that much of an issue, have you considered roughing the surface
> before painting it?
Cant do that. Parts are machined and have to remain smooth
to fit, but must be flat black that will not burnish when touched.
These are interchangable lens housing, grating mounts, etc etc
all in confined light tight boxes.
Thanks -
Pete
> I've seen folks who have used all sorts of things,
> like sawdust and shredded pvc, glued to the inside of the tube and then
> hit with krylon flat black. Works really well.
>
> 'luck - Chris
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Date: 25 Apr 2007 09:52:14
From: Starlord
Subject: Re: Flat Black - where, what ??
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FLAT BLACK sold at wal-mart for just about $1.00 I have used it on my
Stargazer Seve Dob for over 6 years.
--
There are those who believe that life here, began out there, far across the
universe, with tribes of humans, who may have been the forefathers of the
Egyptians, or the Toltecs, or the Mayans. Some believe that they may yet be
brothers of man, who even now fight to survive, somewhere beyond the
heavens.
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Sidewalk Astronomy
www.sidewalkastronomy.info
The Church of Eternity
http://home.inreach.com/starlord/church/Eternity.html
AD World
http://www.adworld.netfirms.com/
"Peter Weld" <hmido@mchsi.com > wrote in message
news:462E5E32.76679D1A@mchsi.com...
> Has anyone found a flat black that will not burnish when touched
> and handled?
>
> In the midwest.
>
> TIA
>
>
>
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Date: 24 Apr 2007 14:48:12
From: Peter Weld
Subject: Re: Flat Black - where, what ??
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Burnishing means: flat black rubs to a reflective glossy surface
when touched which is the very opposite of what and why flat black is
for.
We need a flat black that will not burnish when touched and handled. A
flat black that stays FLAT!
Thanks-
Peter Weld wrote:
> Has anyone found a flat black that will not burnish when touched
> and handled?
>
> In the midwest.
>
> TIA
>
>
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