Telescope Making

Making of Ronchi Grating

More than one method can be used to make a Ronchi grating.

Method 1

One method is to use thin fishing line. For the Ronchi grating described here, fishing line of 0.148 mm diameter has been used which gives 25.4/0.148/2 = 85.8 lines per inch.

Photos

Below is photos of the grating (click of the thumbnails):

Front of grating showing the fishing line grating. Back of the grating. Two plate clamps help to keep the fishing line in place. It has been found that the epoxy alone is not strong enough to keep the line in place.  

 

Making

The grating is made as follows:

  1. Make a 32 x 32 mm square plate and drill a 22 mm hole in it. Drill four 3 mm holes in the corners. Make two 32 x 5 mm plates and drill two 3 mm holes in them. The plate used in the grating is 1.6 mm aluminium. The dimensions is not critical.
  2. A double layer of fishing line must no be wound on the plate. Tie the 2 pieces of fishing line to one corner hole. Wound the 2 pieces as tight and neat to each other as possible. When the other side is reached tie the one piece to the corner hole. Unwound the other piece so that only one piece is left on the plate.
  3. Mix some epoxy and apply it to both sides on the fishing line as in the photos above. Also apply epoxy to the back. Let the epoxy dry.
  4. Fix the two clamp plates with M3 bolts. It may even be better to apply the clamps when the epoxy is still wet. However it was not done with the grating described here.
  5. Cut the fishing line away on the side with the 2 clamps.

Method 2

Another method to make a grating is to print a grating on a transparent film with a printer. A test print wat made with a Inkjet printer. One problem is that the ink would not dry en would smudge when anything comes in contact with it. Another piece of transparent film will have to be placed over it to protect it. A view under the microscope reveals that the printed lines is not continuous but has spaces in them. Thus it is unclear whether this grating would work. Further testing will have to be done.