BoBfest - The Regional Gathering of Amateur Astronomers

Saturday, January 25, 2020
West Wing of Catawba Science Center,
Hickory, North Carolina
Only 214 Days Until BoBfest 2020

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Introducing the Hickory Community Telescope Project!

We are not absolutely certain that this will happen at BoBfest 2019.

The idea here is to construct from scratch a working telescope to be used by the public somewhere and somehow in this area. If we start it, we will begin by grinding the main telescope mirror - maybe an 8 inch diameter.

Our dream is to start rough grinding a telescope mirror during BoBfest! Everyone including children will have the opportunity to help grind this mirror. It will not be completed in one day but all who participate can tell their friends that they helped make a telescope mirror!

Here's about how it will work....
Rough grinding a telescope mirror involves taking two 8 inch diameter by about 1.5 inch thick round pieces of glass known as blanks. One of the blanks is secured to a sturdy table. This mounted blank is known as the tool. Water and coarse abrasive starting with 60 grit are applied to the blank.

The other other blank will become the mirror. It is placed on the tool and simply pushed back and forth with random rotation and position changes. What happens is that the mirror blank on top will begin to hollow out to a concave shape. The tool will round over at the edges to become convex.

This process is repeated for several hours, adding abrasive as needed. The mirror is checked periodically to see if it has the proper shape. Grinding continues until this approximate shape is obtained.

Once the rough curve of the mirror is established, everything is thoroughly cleaned and finer and finer abrasive grits are used until the surface is very smooth and has the correct curve.

The grinding tool is then modified with a grid of pitch or hardened tree resin. Jewelers rouge is then applied and the mirror is very carefully polished until completely smooth.

The final exact shape of the mirror is determined - to an accuracy of abouth one millionth of an inch! - and final delicate corrections are made. This is called figuring the mirror. If it is not done correctly, the mirror will not be good. This is what initially happened to the Hubble Space Telescope!

Once the mirror shape is final, the mirror is sent to be coated with aluminum. When the finished mirror returns, then and only then can construction begin on the telescope!