Lens system project donation?

[David Knaack]

The lens system project is progressing. 

Last time I was at the Makery I went through the donated lenses to clean, catalog and repack them (they are in the Edmund Optics box on the shelf if anyone wants to take a look).

I'm still thinking about the design for the rail mount system. I experimented with mounting lenses in plywood cut by the laser cutter, and that work out brilliantly. I think I'm going to go with that for most of the smaller lenses at least. It should work for the bigger ones too.

So on to the question: Surplus Shed has an educational eyepiece kit for $20 that includes 9 lenses and a nice 4-element objective. These can be combined in different configurations to create different kinds of telescope eyepieces. I think that this would be a good addition to the kit. By assembling an eyepiece and mounting it on the rail with an appropriate objective we could make different kinds of telescope assemblies.

Would anyone be interested in donating a few bucks toward the purchase of this kit? 

 

[Eric Kaplan]

I'm in for $5

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[Dave Thacker]

I'll kick in $5 as well.  

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[Kevin Fusselman]

I'm in as well. I'll take it off your tab :-)

[David Knaack]

Excellent. I placed the order. I put a $2 telescope building book from 1946 on the order too. Maybe it'll have some interesting ideas. $27 total, not including the additional pair of lenses I added for a laser project.

[patrick]

You guys have all the fun.

[David Knaack]

The eyepiece kit arrived on Saturday. It includes a little history of lens development and a list of lens configurations, many of which can be constructed with the kit. I'll have to go through the designs and lenses and see what assembles can be made and see if I can find suitable objectives for them. 

I'd like to see if I can come up with a good way to build mounting hardware that will make it easy to set the lenses together. Many of the configurations have two or more lenses mounted as close together as possible without touching. I'm thinking that mounting them in thin plywood plates or boxes such that the lens surfaces are just inside the bounds of the plate/box would make it easy to stack them in whatever configuration is desired while using only one mounting stand.

On Thu, Feb 14, 2013 at 10:18 AM, David Knaack <david...@gmail.com> wrote:

[Kevin Fusselman]

Remind me again, what's the "objective" of this exercise?

:-)

[Dave Thacker]

I still owe my donation for this.  I've had several conflicts with Makery work days.  Hopefully I'll be over to the space this weekend to pay up.  

Dave

[David Knaack]

There are several. They range from about 7 to over 100mm :D

Once I get things put together, and if there is any interest, I can probably do a short optics talk. I've always found the subject a little mysterious, so perhaps others do too and would be interested in a brief overview of why quality lenses are complicated.

[David Knaack]

Oh, I forgot to mention, the telescope booklet includes some instructions on drilling asbestos, sounds like fun.

[Kevin Fusselman]

Such a presentation sounds really interesting, to me.. Lenses are magic.

[David Knaack]

Keeping the ball rolling.. Thanks to Don who donated a big box of assorted lenses for the project!

I'm still looking for ideas on making a good ground glass. Silicon carbide sandpaper on regular glass kinda works, but the result isn't very bright. Red automotive rubbing compound makes a finer texture, but is extremely tedious. Frosted scotch tape actually works surprisingly well for the level of effort, but it also isn't very bright white. Wax, parchment, and tracing paper all work, but the paper pulp has a very visible texture that isn't ideal.

Anyone have hydrofluoric acid for glass etching that they could bring to the space to etch a few square inches?

Alternatively, if anyone happens to have some ground glass with a nice fine and bright surface, and wouldn't mind parting with it, I've got a use for it!

DK

[Ben Hutcheson]

Have you considered or tried commercial arts-and-crafts glass etchant?  You can get small bottles of Armour Etch brand etchant paste at Hobby Lobby for about $10.  I don't think I have any left, but I remember it leaving a very consistent fine frost effect.

[David Knaack]

I was hoping to obtain a sample of either the result or the etchant before I bought some. Or maybe find someone who had used it themselves and could compare the paste to what I'm getting with sandpaper.

[Ben Hutcheson]

I'll look around and see if I have any hiding in my supplies.

[Steve Sanders]

Saw this the other day.  It's awesome and might even be relevant to your interests:
https://www.youtube.com/watch?v=XFw7U7V1Hok

[Rob Townley]

Great video...  free lenses and other optics all in free projection screen televisions.  Instant fire, boiling water, and melted zinc all in a four minute vid.  awesome.  thanks.
Some screens are better than others as this related video demonstrates:
https://www.youtube.com/watch?NR=1&feature=endscreen&v=xExXjXm0YV0

[Patrick Joseph]

I can get you some lenses also, but not glass.
I use hydrofluoric acid to remove anti-reflective coatings from lenses.
Obviously, it is freaking dangerous.  I wouldn't know how to package it safely.
Even a small amount leaking out of a container could be dangerous.

At 10:26 AM 3/15/2013, you wrote:

Keeping the ball rolling.. Thanks to Don who donated a big box of assorted lenses for the project!

I'm still looking for ideas on making a good ground glass. Silicon carbide sandpaper on regular glass kinda works, but the result isn't very bright. Red automotive rubbing compound makes a finer texture, but is extremely tedious. Frosted scotch tape actually works surprisingly well for the level of effort, but it also isn't very bright white. Wax, parchment, and tracing paper all work, but the paper pulp has a very visible texture that isn't ideal.

Anyone have hydrofluoric acid for glass etching that they could bring to the space to etch a few square inches?

Alternatively, if anyone happens to have some ground glass with a nice fine and bright surface, and wouldn't mind parting with it, I've got a use for it!

DK


On Mon, Feb 25, 2013 at 2:35 PM, Kevin Fusselman <ke...@fusselman.org> wrote:

Such a presentation sounds really interesting, to me.. Lenses are magic.

On Feb 25, 2013 2:12 PM, "David Knaack" <david...@gmail.com> wrote:

Oh, I forgot to mention, the telescope booklet includes some instructions on drilling asbestos, sounds like fun.

On Thu, Feb 14, 2013 at 11:11 AM, David Knaack <david...@gmail.com> wrote:

Excellent. I placed the order. I put a $2 telescope building book from 1946 on the order too. Maybe it'll have some interesting ideas. $27 total, not including the additional pair of lenses I added for a laser project.

On Thu, Feb 14, 2013 at 10:49 AM, Kevin Fusselman <ke...@fusselman.org> wrote:

I'm in as well. I'll take it off your tab :-)

On Feb 14, 2013 10:27 AM, "Dave Thacker" <dtha...@gmail.com> wrote:

I'll kick in $5 as well. 

On Thursday, February 14, 2013, David Knaack wrote:

The lens system project is progressing.

Last time I was at the Makery I went through the donated lenses to clean, catalog and repack them (they are in the Edmund Optics box on the shelf if anyone wants to take a look).

I'm still thinking about the design for the rail mount system. I experimented with mounting lenses in plywood cut by the laser cutter, and that work out brilliantly. I think I'm going to go with that for most of the smaller lenses at least. It should work for the bigger ones too.

So on to the question: Surplus Shed has an educational eyepiece kit for $20 that includes 9 lenses and a nice 4-element objective. These can be combined in different configurations to create different kinds of telescope eyepieces. I think that this would be a good addition to the kit. By assembling an eyepiece and mounting it on the rail with an appropriate objective we could make different kinds of telescope assemblies.

Would anyone be interested in donating a few bucks toward the purchase of this kit?

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[David Knaack]

I was at the craft store the other day, so I went ahead and picked up the little bottle of the usual HF-based etchant, Armour Etch. I forgot that they had these inexpensive little bottles of it.

It occurs to me that if someone was looking to do decorative glass etching, a bit of contact paper and the laser cutter or cricut would make it very easy to do. We should do some OMG beer glasses or something. 

[Ben Hutcheson]

I actually did just that with some Christmas ornaments a couple months ago.  I cut stencils out of that pink vinyl we've had sitting around and used it as a mask to etch glass ornaments.  It worked quite nicely, although I was trying to cut details finer than the Cricut could really handle.  The laser would do better for resolution, if you could get a clean cut in your stencil material.

[David Knaack]

The etch works very nicely for this purpose. The frosted surface is more opaque than what I was getting with either silicon carbide sand paper or red automotive rubbing compound. I think this sort of ground glass screen can also be prepared with media blasting, but I don't have any media that is consistent and fine. That's ok though, this looks like it will work very nicely.

Next up is to mount some lenses in holders and get the holders put on the rails.

[Eric Kaplan]

I don't know the specs on our blast media here at work, but I'd be happy to run some sample parts through it for you if you want to try some.

[Matt Hester]

Here's a projection tv on CraigsList $25 bucks. Might be good for
components.

http://omaha.craigslist.org/zip/3651344518.html