Adventures in Optics

That 52mm 152mm F.L. achromatic lens arrived Monday.  It seems a decent piece of glass for its intended purpose: a wide angle low power finderscope.  I had considered making the rest of the scope from carbon fiber composite, but this is perilously close to polishing a cow pie to perfect brilliance.   It turns out that perfectly respectable refractors can be made from lens like this and PVC plumbing pipe.  SCHEDULE 40 pipe in 2" nominal diameter is just about exactly the right size for this.  A 2" to 1" nominal size coupler allows you to use a PVC tube that is 1.31" OD.  To make go through the coupler I will bore through the coupler.   The 1" nominal tube will need boring to accept the 1.25" eyepiece.  I will tap the coupler to accept a thumb screw.  This will five a drawtube for coarse focus.  I have a helical focuser that goes into the draw tube for getting this nice and sharp.

Another fitting whose purpose is unclear (at least for plumbing) is the right ID for the achromat lens to rest in it.  I will put some 52mm O-rings at the front to hold the lens in place.  I need to figure some way to add set screws for adjusting the collimation of the lens to the tube.  I suspect my solution will only be approximate and that is probably good enough for intended purpose