On my trip to HomeDepot the finest grit sandpaper I could find was 400 grit. It seemed to work well.
Mike

If not using sandblasted or chemically etched glass, I would be inclined to get hold of some 600 grade lapidary grit (silicon carbide), clamp two clear CD disks back to back with a firm seal around the inner hub and outer diameter edges, put a bunch of bearing balls into a gemstone tumbler barrel with the grit and water, turn it on and leave it to its own devices for a few hours.

As long as the two disks have not moved against each other or grit got in between them, you should end up with two clear disks with a translucent surface on one side and smooth on the other.

I would do only one pair in a barrel at a time as sliding edges will cause long scratches not short pitts.

Just a thought.

i am using 2 AAA batteries (1.5 volts each) on the cd motor and I think thats going too fast and making more noise then it should... not nearly as much as the radio shack kiddie motors but noticable noise... any suggestions?

BTW: What project box size you guys using?

Bob, you're actually close to the mark on how to create real ground glass. You basically take the grit, add a bit of water, and rub two pieces of glass together for about 20 minutes. Using that method you can create better-than-professional-grade true GG, if you take your time at it :-)

paulb

<<<-- Originally posted by Peter Sciretta : i am using 2 AAA batteries (1.5 volts each) on the cd motor and I think thats going too fast and making more noise then it should... not nearly as much as the radio shack kiddie motors but noticable noise... any suggestions?

BTW: What project box size you guys using? -->>>

7x5x3, its takes a bit of heat to make the GG fit without rubbing

Using a 9v battery....
 

may burn the motor out if it doesn't it will spin REALLY FAST!

I took the motor/CD holder out of an old portable CD player, snapped a CD into it and connected it to 3v. WHOA! It spins too fast. The gyroscopic effect was very pronounced and I was concened if my"Agus35 Mark 12 Pro Rev 1.0" was jerked to quickly the CD might come of holder!

I then connected it to a single 1.5v cell and its much better. It still spins at a good rate.

Tom

www.elpez.com/agus35test.mpg linked

Here are two pictures of my quick-and-dirty attempt to make one of these things. It works! Now I'm going to spend a few dollars and make a nice one.

The lense was biult into a 35mm camera and by the time I wrestled it out it could no longer be focused. I changed the motor on it and had to mount the lense backward to get it far enough from the GG. The big gash in the side is from only having 100 packs of CDs and having to cut a huge hole to shove my camera into.

http://vistatheater.org/~rhenry/agus...35-1-front.jpg
http://vistatheater.org/~rhenry/agus...s35-1-side.jpg

For those looking for fine grit sandpaper, try the auto parts store in the paint section. They usually have really fine grit wet/dry paper for doing touch up or other paint/body work. I have gotten 1000 grit at auto part stores before. They should at least have 600...

I added an adjustable fresnel lens

http://www.imagestation.com/picture/...8/fa528f0c.jpg

edited to say: HELL YEA! thats what i needed! its adjusted out a little over 1/4". This fixed any vignetting.

<<<-- Originally posted by J. Clayton Stansberry : John,

A couple of questions:
1. Where did you get the freznel lens?
2. Where did you get the fan?
3. Is the box the one from Radio Shack?
4. When are we going to see some footage with the fix?
5. Plans?

Agus,
How are your plans coming?

Thanks in advance...
Clay -->>>

1-Walgreens $1.50
2-computer store
3-radio shack
4-I need a better GG, so in a while
5-Just look at the pictures for now

<<<-- Originally posted by Paul Bettner : Hey John, what tool did you use to cut such perfect holes in the box? -->>>

I used a hole saw attachment on my milling machine, a drill should work tho

<<<-- Originally posted by Peter A. Smith : John what's the size of the fresnel lens 2x3? -->>>

it was 2x3 :) then I cut it up into 2x2

http://scientificsonline.com/search.asp?t=ss&ss=fresnel+lens

Here's are several decent Fresnel lenses you can get and then cut down to what size you need.

Here's another place as well:

http://www.3dlens.com/fresnellens.htm

Do you see the lines from the fresnel lens on your recorded image?

To invert the image you could also inster a dove prism in between the GG and the camcorder lens or fresnel:

http://www.optosigma.com/miva/merchant.mv?Screen=PROD&Store_Code=OS&Product_Code=pg137&Category_Code=Dove+Prisms