Poor man's LED aligment tool

I just finished a prototype of a Poor man's LED alignment tools and it works
beautifully!!   It is nothing extraordinary but thought to post a
description for the sake of those that like me are looking for a cheap way
to align their enlarger.

Took a piece of plywood 1/8"x5"x5", made a 1/2" hole at its center and 4
holes 1.5" from the center and equidistant from each other, these holes were
just big enough to allow the insertion of  4 standard LED's (one in each
hole), the LEDs were series connected, a 50 resistor was added to the
circuit to limit the current and LEDS+resistor fed by a 9volts battery. The
configuration of holes of the piece of wood was replicated at the end  side
on one of the mirrors, holes were not made on the mirror, instead its
backing was scrapped.  The piece of wood with the circuit was glued onto the
mirror.  I happened to have the prism of my defunct very first SLR (Minolta
XG2), I placed this prism on the center hole of the piece of wood and can
see very clearly the alignment dots-cross pattern thru the prism.  A prism
is not absolutely necessary, one can peek from above the mirror and thru its
center hole, but a prism make the alignment so much easier.  A prism can be
easily obtained from a defunct SLR camera, eBay lists many broken SLRs going
for very little money.  Edmund Sci. has a right angle prism for about $10,
this place also sells surplus prisms http://www.anchoroptics.com/

Guillermo