ATM another newbe question

["john" <jp@premier1.net>]

ive made a focal tester.
my lightbulb is inbedded into a piece of 3/4 inch cherry block,
above that i have a 3/4 hole too look through,
my blade is screwed into the face of the block,
(on the mirror side of the 3/4 block)
is it too far from my eye too do me anygood,?
,
when i put a ronchi screen 25lines per inch in place of the blade,
i see no lines,
if i pull away from the bulb about 2-3 inches then i see lines,
i looked at mells tester but couldent see enought to figure anything out,
if i build another light platform ,
can the light be further back,?
,
as long as the light and screen moves,togeather.
or does the screen have to be at the light source for accurate
measurements,.?
,
for some reason im interpeting that you have the screen over the light
source,
and up into the viewing hole also,
tell me im confused here also.
.
thanks in advance,
john pike.
marysville wa.
cold and rainy, a fine polishing day,
i really need to buy that book.