The Low-Profile Focuser

 I am machining it mostly from acetal (black already, low density, easy to machine).  It will start as a block with the same footprint as the current focuser, so I can reuse the existing holes, and 1" tall.  Then I will drill a 1.5" diameter hole through,then  turn a piece of 1.75" long aluminum tube to 1.49" OD, 1.255" ID.  (I want a loose fit for eyepieces; they will held in place by a 8-32 set screw.)  One end of the tube will have a collar 1.6" OD and perhaps .1" long, so it cannot fall through the base block.  Then drill and tap a 1/4"-20 hole in the side of the base block for a set screw to lock the tube in place.  This is the coarse adjustment.  The aluminum tube needs to be black.  If I can talk myself into learning how to anodize at home, great!  If not, flat black paint.  I will likely need to see how thick the paint dries before turning final OD.

I will then buy one of the helical focusers that slide into a 1,25" focuser.  This will provide fine adjustment.  With this combination of coarse and fine adjustment, I really do not need a rack and pinion or Crayford focuser.  

I have parfocalizing rings on most of my eyepieces so they come to same focal point in the focuser.  There are a couple odd ones that are simply outside the normal range (like the 35mm Super Plossl that focuses way in from the other eyepieces.  Hence the coarse adjustment.  This looks like fun!