Wednesday, September 9, 2009

Got Grit

After a brief delay in getting our grinding abrasives, we have resumed our telescope project. In the picture, you can see the mirror blank in the middle. Above the blank is optical pitch. It is literally tree sap and will be used in polishing and figuring the mirror.

To the left of the mirror are the abrasives used in rough grinding. This abrasive is made of Silicon Carbide and are graded by size. We will be using 60, 120, and 220. If you imagine sand paper, it is graded the same way, I believe. So the 60 grit abrasive feels the same to the fingers as 60 grade sand paper.

To the right of the blank are the abrasives that we will be using in the fine grinding and polishing. Three are made of White Aluminium Oxide. We will be using 25, 15, and 9 in the fine grinding. We will be using Cesium Oxide in the polishing.

The Amateur Telescope Makers website (http://www.atmsite.org/) has a number of links to suppliers. I considered 2, Willmann-Bell (http://www.willbell.com/Default.htm) and GotGrit.com (http://gotgrit.com/). Ultimately, I choose GotGrit. The owner, Tom Moulton, is an ATM (amateur telescope maker) himself and his prices were as good or better than the others. Just be aware that he usually ships orders out on Saturday.
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Naming a Blog

Choosing a name for a blog is very difficult and fraught with dangers, but in consulting with Mary Kathryn, my dear bride, we decided on "Kenning through Astronomy Divine."

The name comes from Meditation 6 by Edward Taylor, a New England Puritan, pastor, and physician. Every week he walked hunderds of miles to tend to his flock and care for the sick, and he still had time to be a prolific writer.

About Our Project

In 1978, when I was 12, I bought a book on telescope making at Davis Planetarium in Jackson, MS. It started me on a quest to grind my own telescope mirror. Two years later I order a 6 inch mirror blank and abrasives from Edmund's Scientific only to be crushed when the blank arrived without the abrasives. Edmund's had stopped carrying them. Over the next 30 years, I had thought about grinding that mirror that I had been carrying around for so long. Now as part of a homeschool Astronomy class with my children, we will complete a project 32 years in the making. I hope you all enjoy following our progress in this. We hope that it culminates in February or March with a West Virginia Star Party that will include some of my nieces and nephews.

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