Aperture Fever

Aperture fever

Aperture fever is what you get when you want to see more with the telescope you have made and find that you are not satisfied with what you see. It is also a disease suffered by ATM’ers who are more inclined to find satisfaction in making than in observing.

Pictured above is my latest work in progress. A 10 inch (well, only 9.5 inches, actually) blank hoggged with 60 grit to a depth of 2mm in the centre. The ruler above is a 12 inch footrule, and the little thing lying on the mirror is a 2mm drill bit whose end just slides into the gap between the edge of the ruler and the glass.

The weird cylindrical object on the left is the tool used for hogging out the blank.

An iron pipe, 1 and 3/4 inches in diameter.  It is a standard plumbing item, threaded at both ends, and is available in all hardware shops. One end of it is covered with an iron cap, which has been welded on to it, and the other end is open.

The tool is held in the hand and the flat cap is used to crush and grind the grit on the glass surface. The activity is similar to what is done when crushing plants and herbs in order to extract their juices (using a mortar and pestle) , or for making chutney on a stone slab with a stone roller. (the word chutney, by the way, has made it into the Oxford, so I will not explain further).

This page is under construction, and will be updated periodically.

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