Lurking Optics Experts?

[Thomas Droege <tdroege2@earthlink.net>]

The Big Black Box (BBB) is now working and I have checked out my first
spare board.  Things should now go more easily for fixing boards in the
system.  I can be pretty sure that a board works if I can get an image in
the BBB.  

If there are any optics experts lurking, my brother and I have been having
a discussion about what to expect when a lens designed to focus at infinity
is set up in the BBB where the object is only about 4 focal lengths away. 
Lee points out that all those lenses are set up to get a good image at
infinity.  For close ups, things need to be moved around.  Our narrow
bandwidth might help somewhat?  

In any case, I get a pretty broad focus in the box looking at the test
screen 4 focal lengths away.  The V lens is soft like the I lens is
normally.  Not an awful focus, but not as sharp as I expected.  Any coments
from experts, or those who just want to put in their opinion?

Note that the others trying to do all sky surveys are mostly using
paparatzzi type camera lenses.  These attempt to be color corrected over
the full optical spectrum.  This is tough and even though such lenses use
many more elements than we do (with the resulting light loss) they have to
give up on something.  Whe is lost is a flat field.  If you have Princes Di
in the field, you don't put her in one corner.  Who cares that the objects
in the corners are a little dim.  So such lenses are down 40-60% in the
corners, while we are down 5-10%.  This should help us.  

Tom Droege


Tom  Droege Jennifer Malpass
tdroege2@earthlink.net