(Nikos Aslanakis) wrote in message om...

BUT when I try the 11mm TV with the Barlow on Mars I get a BIGGER
planetary disk than with the 4mm eyepiece. I can tell this because
with my other eye I can compare the planet to the holes on the tripod.

I have carefully measured the magnification of my "2X" Ultima
Barlow at anywhere from 2.4X to 2.6X, depending on which eyepiece
it is coupled with. Note that the magnification is extremely
sensitive to the distance between the Barlow and the field lens
of the EP; you can boost it quite perceptibly by pulling the
eyepiece 1/8 inch out of the Barlow's barrel.

Also, I wouldn't trust the 4mm stamped on a cheap eyepiece farther
than I can throw it.

- Tony Flanders