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Flocking

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#1 Guest_**DONOTDELETE**_*

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Posted 01 February 2004 - 10:37 AM

In one of the light pollution threads running here, flocking the inside of the tube was mentioned. What is this? How do you tell if it has already been done?

#2 litespeed

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Posted 01 February 2004 - 11:15 AM

Roughing up the inside of the tube to absorb light and or prevent light scatter.

You can buy a paper. Or with paint (thick and knarly). There are lots of ways to do it.

Do a search and a bunch should come up.

AJ

#3 Guest_**DONOTDELETE**_*

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Posted 01 February 2004 - 11:28 AM

Flocking is usually a black flocking paper. On your dob, the tube is probably painted black, but the inside surface may be smooth. To enhance contrast with a reflector, flocking is often recommened, or repainting with a good dead-black paint. The rough surface of the paper helps cut down light scatter. It acts like a bunch of tiny baffles inside the tube, much like eyepieces have blackened threads in their barrels.

To boost your contrast you should 1.) cap the rear of the tube so that light from the ground doesn't get up to the secondary mirror and the eyepiece, 2.) flock the tube or install baffles, though some use crushed walnut shells embedded in black paint, or similar jagged material, which will, again, reduce light scatter.

To use crushed walnut shells or similar, paint the inside of the tube with a dead-black paint. While the paint is still wet, dump the crushed shells inside the tube and roll it around so the material is embedded in the paint. Let the paint dry, and brush out the loose material. Apply a coat of paint over the embedded material, and let dry. A second coat may be applied if needed. This will give you a very rough, non-reflective dead-black interior that will enhance contrast. Flocking paper is probably cheaper, easier, and lighter, and may work just as well. Baffles may be "ideal" but take some effort to calculate where to place them, how large to make them, and then you have to install them accurately.



#4 Scott Hamilton

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Posted 01 February 2004 - 11:34 AM

As long as we're on the subject, does anyone know if baffles can be
purchased for a reasonable price?

The Newt program will calculate their dimensions and placement but
I can't imagine trying to make them myself.

Scott

#5 Guest_**DONOTDELETE**_*

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Posted 01 February 2004 - 11:38 AM

I think that's why the crushed walnut shell thing got started.

#6 litespeed

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Posted 01 February 2004 - 11:54 AM

Scott,

You should contact Schultze. He has made some baffling. Did a beautiful job too.

Looks to be fairly easy.

AJ

#7 BCB

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Posted 01 February 2004 - 12:10 PM

I can't see installing regular baffling in a newt.. You will cut off the incoming lightpath to the outer edge of the mirror.. At first thought it makes sense, till you think about it.. You'll basically block the whole mirror between the baffling, and secondary..

Stick with reg flocking..

Would blotter paper painted black make for good flocking ???

#8 Guest_**DONOTDELETE**_*

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Posted 01 February 2004 - 12:29 PM

All the baffle rings will be larger than the primary's diamater, and none will intrude into the light cone. They won't change in diameter like a refractor's will. They are just to keep stray light off the inside of the tube wall so that the stray light won't get scattered and get to the eyepiece.

I don't know how blotter paper would react to being painted. I'd suspect that any rough surface could be painted, or painted onto, the inside of the tube.

I suppose you could even put a piece of self-adhesive black felt opposite the focuser so the eyepiece cannot see any stray reflections from the opposite tube wall. Many low-power, wide-field eyepieces have a field of view wider than the size of the secondary. So if you put a patch of something really black, like felt, on the tube wall opposite the focuser, you may be able to increase the contrast of the telescope with little expense or effort. And cap the mirror-end of the tube, or put a small baffle outside the mirror, of course, to keep light reflected from the ground out of the tube.

#9 jmoore

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Posted 01 February 2004 - 01:40 PM

This is great info...I was wondering the same things. I might try the crushed walnut in my Newt. Otherwise, if you say that I can get baffle rings of smaller diameter than my mirror, maybe I'll go that route. I guess these would just protrude < 1/2" from the scope walls then?

I also wish to increase baffling for my little 80mm refractor. It's a daytime spotter, so I think its baffling is inadequate. I get some glare when looking at Saturn. Any ideas how to increase baffling here? I don't want want to take the scope apart (don't think I could anyway), but could I create a well-baffled dew-shield or something? Would this help? Any pointers on doing so?

thanks
jeff

#10 litespeed

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Posted 01 February 2004 - 02:16 PM

Here is a good example of baffling on a dew shield for a refractor:

http://www.cloudynig...rt=7&thecat=504

Baffling for the inside of a newt. will be very similar. Here is a shot of a dob. with baffling and the roughed up paint I was speaking of earlier (Krylon). :p

AJ

Attached Thumbnails

  • 48416-baffle.jpg


#11 jmoore

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Posted 01 February 2004 - 02:21 PM

nice, AJ.

how do you make the actual baffles?

#12 litespeed

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Posted 01 February 2004 - 02:35 PM

Jeff,

That scope is not mine. They used thin plywood for the baffles. I am doing something very similar on the 10" scope I'm currently building. I used thin sheet balsa on mine. Easy to cut and very light weight. I have about 4 more in mine than the one in the picture (they are cut out but not installed yet).

There are a number of good materials you can use to make the baffles.

AJ

#13 Guest_**DONOTDELETE**_*

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Posted 01 February 2004 - 02:48 PM

Similar to the walnut idea, I used the "sawdust" method. First, you mix basic white glue and water so it's thin enough to brush easily, then brush the glue mix on to the inside of the tube. While this is wet, put a lot of sawdust inside the tube and roll or shake it to get the sawdust to stick to the wet glue (I did it in small sections at a time, starting in the center of the tube and working toward the ends).

After this has a chance to dry, then two coats of krylon ultra-flat black paint to give it the deep black as well as grab on to all the bits of sawdust and help hold them down.

When it all nice and dry, I gave the tube some nice thumps to get any loose stuff out.

I liked the sawdust idea better than walnuts because the particles are finer and, I thought, would stick better.

It works like a charm, was an easy afternoon project and cost about $10 for paint and glue. Flocking paper is cool, but it would have run about $50 for enough to do my whole tube...

BTW, I did this 5 years ago, and it's held up quite well.

#14 Relativist

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Posted 01 February 2004 - 04:02 PM

It's simple buy this:

http://www.fpi-proto...com/flocked.htm

remove all the stuff in your tube and coat the inside of the tube with it. Also if you make a dew/stray light sheild like shown above you can flock it also. Somepeople flock the inside of the focuser, and their barlows.


.....Curtis

#15 eric moerman

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Posted 01 February 2004 - 04:56 PM

hello ,

you can make baffels simply from thin plywood.
The inside ring should be cut out under a sharp angle so that you get a sharp edge.
They should al have different diam.otherwise they will vinget your FOV.
the biggest one should be at the front of the tube.
Its a loth of work buth deffently worth it.
For the inside you can use also black velvet,easy to work with and the darkest material you can find.Just dont try to glue it in verry flat,you should have some bumps,they will act in some way as baffels.
I included a picture of the baffels in my scope.
Greatings,eric

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  • 48476-eric7.jpg


#16 jmoore

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Posted 01 February 2004 - 05:32 PM

how many baffles is enough? I imagine the more the merrier, but realistically...with an 8" f5 Newt for example...3, 5, 10?

What's the best way to attach the baffles to the tube, once you've got them cut? Just wood glue or something?

Why would the diameter of baffles affect vignetting if they're all more open/narrower (larger inside diameter) than the primary? Anyway, by "front" of tube, do you mean the end with the secondary...closest to the sky? or do you mean the end that's closest to the primary?

#17 eric moerman

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Posted 01 February 2004 - 05:57 PM

mr.Moore

It depends on how big (diam.)your tube is and how high your focuser is.
you can calculate everyting with the newton desing program.
I always glue them in with sillicone(i dont know how they name this in english).just cut them pretty close to the inside diam.of your tube and then put sillicone to the corners.
With the front i mean the open end where the focuser(for a newt)is.
if you should put a baffel whit the same diam. in the front of your tube it will vinget the FOV.Its difficult or me to explain in english but you can compare it whit when you should look tru a long pipe,you will have a bigger field of vieuw whitout a baffel in front then when you should put a baffel there whit the diam. of your eye.
Now you could say that you should not put any baffel there at al but then you loose the effect ofcorse.
try to imagen that if you could make yourself small enouf to stand on one edge of your mirror (whipe your feeth first :lol:)looking at the open end of your tube,you should not be abel to see any part of the tube wall,you should always look at the back of a baffel.
My english writing gets worse and worse,sorry for that.
eric

#18 litespeed

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Posted 01 February 2004 - 06:17 PM

hello ,

you can make baffels simply from thin plywood.
The inside ring should be cut out under a sharp angle so that you get a sharp edge.
They should al have different diam.otherwise they will vinget your FOV.
the biggest one should be at the front of the tube.
Its a loth of work buth deffently worth it.
For the inside you can use also black velvet,easy to work with and the darkest material you can find.Just dont try to glue it in verry flat,you should have some bumps,they will act in some way as baffels.
I included a picture of the baffels in my scope.
Greatings,eric


Hey......

That looks like my garage!!

LOL...... :lol:

AJ

#19 Guest_**DONOTDELETE**_*

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Posted 01 February 2004 - 06:18 PM

You guys blow me away with all your knowledge. I have never seen this in any book or telescope article I've read.

Those of you with Hardin Dobs have you done this? They look nice and flat black to me. Can you physically tell the difference (on a mass produced scope) or is this more of a mental thing? Not doubting you all but if this is necessary why isn't it factory applied? - well the obvious answer is $$$

#20 eric moerman

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Posted 01 February 2004 - 06:37 PM

Kevin,

you can really see the difference if you do it right.
One time on a local star party somebody asked me to see M42.
he had been looking at it in hese telescope (also a 12.5") and than he looked true my telescope.
The first he asked me was"your using a OIII filter?".
Thats the difference.

eric


#21 eric moerman

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Posted 01 February 2004 - 06:44 PM

Kevin,

there are some manufacterers that do al this(Lightspeed,parrallax instr.)
The reason most of them dont do it is as you already mentiond $$$$
it take's a loth of thime and effort to puth baffels in if you want to do it right.
If you want to learn how to calculete you can find everyting in the book"telescope optics" from Rutten and van venrooij

#22 Relativist

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Posted 01 February 2004 - 09:16 PM

Um, I don't know about the rest of these guys, but I'm just going by what I've found on the internet, you should check they skyquest telescope yahoo group, they have links to modded GS/Synta Dobs, One of the other nice things you can do is put a knob so you don't have to put your hand on the OTA and make currents when you point the scope. Of course, I think another very important thing to do is have some sort of tracking, weather it's a platform or motors is up to you.


..........Curtis

#23 erik

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Posted 01 February 2004 - 10:03 PM

just a question about using baffles as opposed to flocking paper.even if they didn't enter the light path, wouldn't the baffles potentially interfere with the warm air that circulates along the edge of the tube, smearing detail, and making cooldown times slightly longer?isn't that one of the reasons that they make the tubes oversized?its probably minor, but maybe something to consider.-erik wilcox

#24 rboe

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Posted 01 February 2004 - 10:54 PM

Nobody mentioned black foam core matt board. I would think it would be easier to fab than plywood, cheaper and lighter.

Is it just over looked or avoided for some reason?

#25 litespeed

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Posted 02 February 2004 - 08:23 AM

Jeff,



There are a number of good materials you can use to make the baffles.

AJ


Nope..... Not overlooked......

AJ


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