Gluing the ronchi grating.  

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Here we have the materials assembled including a 100 line per inch ronchi grating from Edmunds Scientific.

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We drill holes around the periphery of the center of the gallon can lid.

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Next we snip out the center of the lid.

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We have unscrewed the tube from an eyepiece.  The lid is loose on the eyepiece tube.

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We crimp the lid edge in three places and then test on the eyepiece tube.

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OK, Its just snug now.

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Next the RTV sealant.

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And smear it around the edge with my finger.
Wipe off your fingers.

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And drop the ronchi grating in the center carefully to keep the glue from the grating center. The lined side of the grating is on the inside of the cap.

Now put a plastic cup over it and come back tomorrow.

Making a knife edge for testing your telescope is even easier and cheaper than making a grating.  Use another gallon can lid and proceed as before.  Be sure to sand or grind away the sharp utility knife points.

 

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