Adding fine crosshairs

[sculptor]

Trying to glue fine copper wire crosshairs onto a ferrule to fit a 50mm barrel. Out of superglue. Reach for horrible stringy snotty syrupy acrylic glue. Gets everywhere. :mad2: Keeps forming fine threads exactly where I want the crosshairs ... DOH!

Throw out copper wire. Pretend to be silkworm. Dab nozzle at one edge of ferrule. Draw stringy strand of clear acrylic "silk" across tube and dab on other side. Repeat at 90 deg. Two strands bond together so centre will not flop about. As strands dry, they pull very tight and straight. (Don't try this with the ferrule in the eyepiece, or goodbye lenses!)

Spider, spider, twisting tight, in the eyepiece of the night, to misquote MacNiece and Blake.

The 'silk' threads are much thicker at the edges, so you can find them, but transparent and much thinner in the middle, so they don't obscure the alignment star! :thumbsup:

[bojan]

Why don't you try a cob web? It is not hard to persuade the little spiders to contribute some silk, especially in this part of the year.

Another way to obtain the thin transparent fibers could be to try and find optical cable with suitable lightguide strand, but it is not easy as today they use only plastic and quite thick fibers.
Or to make one of your own, from old bulb glass, it is easy to melt on alcohol flame... the procedure is the same as you described for thick glue.