ATM FOCAL PLANE QUESTIONS

["(RIA) Durkin, Kenneth M" <k.durkin@state.gov>]

I have just about completed my 8" F7 Dobsonian.  I did the calculations for
the focuser hole and cut it in what should be the right place.  I am waiting
for the eyepieces (orion plossl 7.5, 17 and 26 mm,  to arrive), but in the
meantime, since I find it hard to do nothing on my treasured telescope
project, I want to verify that the focuser hole is in the right spot for the
eye-piece to pick up the focal plane.  Yes, yes, I've done the math, but I
want to know that it actually works, and I want to know now, before my
eyepieces arrive. 

When the primary and secondary are installed I can look through the focuser
tube (no eyepiece)  and see whatever the telescope is aimed at.  What
concerns me is that when I took an eye-piece off of an old, but working  35
X 50 pair of binoculars and set it on the focuser tube for fun (it does not
fit into the tube because of an oversized mount on the binocular eyepiece)
I could see nothing at all, no matter how far in or out I moved the focuser
tube.   Is this cause for alarm?  Even though I haven't collimated the
primary mirror yet, surely I should see something.  Before installing the
primary and cutting the sonotube, I checked the focal length of the primary
using a flashlight and a piece of paper.  It was within one-eight inch of 56
inches, so I used the 56 inch number (trusting Coulter more than my shaking
hand).  Even if its off, while the focal plane may not be centered, I should
at least see it, right?   

Most important, and please please answer this - is there any way to actually
see where that focal plane is inside the main tube before making another
hole, if necessary,  in the main tube?

                                Thanks,

                                Ken