grinding my own lens ? grinding my own lens !

[Mongo]

The book "Primitive Photography" has a section on some of the classic lens designs. The assumption in the book is that you'll buy the individual elements already made (not at all far-fetched...SurplusShed sells lots of individual lens elements in many sizes and focal lengths) and build the lens from those. No Hyper- or Metro-gons, but a few classic designs that should give you a good foundation to work from. The books well worth it as the ultimate "build everything yourself from scratch" resource...it even gives detailed instructions on making your own paper negatives.

Using the book, your time, and very little money, you could be making prints using negatives you coated, shot in a camera you built with a lens that you built and a negative holder that you built. Pretty fun stuff to read even if you never intend to do any of it. And it's the ultimate antidote to digital angst...even if every supplier in the world gets out of the analog photography business, you'll be able to make pictures using the instructions in the book.

Be well.
Dave

[Rock Poper]

you could be making prints using negatives you coated, shot in a camera you built with a lens that you built and a negative holder that you built.

thats the idea! - neg's I coated ? thats one I hadnt thought about yet -

[phfitz]

Lee L:

thanks for the link, the program looks interesting. 10 surfaces would cover Heliar, maybe I can find the reason for the magic;-))

Now to find what to polish a lens with and where to get it. Any ideas people?

Thanks.

[Lee L]

Lee L:

thanks for the link, the program looks interesting. 10 surfaces would cover Heliar, maybe I can find the reason for the magic;-))

Now to find what to polish a lens with and where to get it. Any ideas people?

Thanks.

Willman-Bell has stuff for making astronomical optics, especially mirrors, that might be applicable to refractive lenses as well. However, I don't know where to find that part of their catalog online. Find them online and ask for a copy of their catalog, which lists those supplies.

I'm sure there are other suppliers, but I don't know them off the top of my head.

Lee

[Donald Qualls]

Yep, look up astronomical suppliers. There used to be a place called "got-grit.com" (give or take a hyphen) that would sell all the grits you could want from 60 carborundum down to rouge. For grinding a lens, you're going to want 60 to 90 for roughing, then 120, 220, 320, 600 (silicon carbide to this point), 15 micron, 10 micron, and 5 micron (aluminum oxide for the fine stuff). Some folks use 3 micron alox as well.

Once you're done removing glass, you'll need to polish; that calls for optical pitch (though I've heard of one fellow successfully using road tar and another tempering roofing tar to get usable pitch) and some kind of rouge. The most common now is cerium oxide, but some folks use tin oxide and a few prefer to finish with genuine rouge, an iron oxide compound (but watch out for lumps in the red rouge, they'll scratch your glass).

I'd also very strongly recommend working with a local telescope making group to gain the hands-on experience you'll need to make a lens. A simple lens (one element, plano-convex, like the objectives Galileo used 400 years ago) isn't difficult to make, but if you want to make an achromat or more complicate lens you'll be looking at developing some considerable skill before you get one that's usable.

[Murray@uptowngallery]

Do not breath dust from the very fine grit. In particular, cerium oxide at the fineness used is bad news for lungs. I read also it's slightly radioactive. The jeweler/gemologist who gave me some only knew about the lung issue.

[Donald Qualls]

Given that the grits are used wet, this isn't a significant problem during actual work. Letting the grit dry on the work surface is probably a bad move, and one should avoid breathing the dust (or any fine mineral dust, for that matter) from the supply cannister...

[phfitz]

Hi there,

Thanks to everyone for the info. I found everything at a lapidary supply shop in town, just look in the phone book under lapidary, jem stones, rock polishing, you may have a local store.

I just wanted to polish out some cleaning marks from a 100 year old B&L Tessar. I will use a 2 part acrylic/urethane seam sealer instead of pitch and see how that works out. I don't like the idea of cooking up roof tar, it would smell like death.

Have a weekend.

[fparnold]

I'm sure there's a modern equivalent, but for pitch you might want to look for Bassists' Rosin. When I was trying to finish a mirror another telescope maker hadn't, I had a box of pitch and my brother, the Bass player, borrowed some chunks to use as rosin. Said it had the same texture and behaviour as the official stuff.

[Sparky]

My father told me when he was very young, that astronomers of old started out by taking two flat lens blanks and rubbing them together. Interestingly, one would take on a convex, and the other a concave, curvature after a short while.

I wonder if this might be the key to getting a good quality cementable surface between two adjacent elements.