Re: (ATM)Dark Tube Linings
Chuck Grant (grant@aretha.llnl.gov)
Mon, 21 Aug 1995 15:45:15 -0700
> From: Doug Ferrell <dferrell@adoc.xerox.com>
>
> >
> > Tried it -- it shed hair...
> >
> > Steve <sft@aegis1.demon.co.uk>
>
>
> I have a 12x12" piece of black felt glued in my 10" Coulter's
> tube directly across from the focuser--makes a huge difference when the
> upstairs neighbors' lights are on. The felt I bought had shiny filaments
> so I gave it a quick, light coat of flat black paint. This should also
> help with the shedding problem. The difference between the flat black
> painted parts of the tube and the felt are obvious at all angles. I also
> added three baffles of 1/4"x1/2" foam weather stripping which seem to
> help (though the adhesive tends to release sometimes).
> On my new scope (under construction) I will have to try velvet.
> Where's a good source and how do you attach it? Won't glue seep through
> it? How much does it cost, typically?
>
> Doug Ferrell Xerox Desktop Document Systems
> dferrell@adoc.xerox.com Palo Alto, CA
>
The desirable property of velvet is that light tends to be reflected
back along the path from which it came, rather than on down the tube.
Felt does not have this property, but is very rough and traps the light
with multiple reflections. A thin coat of good flat black spray paint
will make the felt "blacker." A thick coat will make the surface too
smooth.
Even though velvet looks shiny at some angles, do *NOT* apply flat
black paint to velvet, as this will destroy the retroreflection property.
I usually find velvet at fabric stores. It is fairly expensive for
fabric.
Chuck