As with Tele Vue's NP101 I reviewed for Sky and
Telescope a few years ago, the optics in the NP127 are pretty easy to
test: bottom line is that they are about as perfect as optics get.
There is no false color at all, either in focus or in the extra-focal
diffraction disks on either side of focus, even with a 3mm Radian
eyepiece. For color correction in an apo refractor, I've not seen
anything better and many triplet apos are slightly worse.
There was no sign of astigmatism and little indication of spherical
aberration. In focus, the Airy disk and rings looked nearly textbook
perfect, marred only by some initial tube currents and seeing. But the
scope settles down quickly. Still, on my one night of testing, by the
time my coffee break for letting the scope settle was over, the seeing
began to get worse. But for a short while I did enjoy good seeing and
could tell the optics were delivering nearly perfect images in a star
test. While the seeing was good, Saturn looked great! Very cleanly
defined with the Cassini Division and ring shadow easily visible.
This is a great scope for use at all magnifications. On the low-power
end, I tried both the 41mm Panoptic and 31mm Nagler. I'd have to go
with the Nagler easily (after all, it's only money!). While the
Panoptic provides a slightly wider actual field, the Nagler is very
close in true field, and its wider apparent field simply makes it more
impressive to look through and provides a better "panoramic" experience
I think. Both eyepieces nicely framed all three stars in Orion's Belt
with room to spare -- quite an impressive field.
But note, some star diagonals (the William Optics ones) have a larger
than needed field stop in them and will vignette the outer field of the
41mm slightly (with its large field lens), cutting down its true field
and giving it a softly-defined outer edge. The 31mm Nagler works fine
with the WO diagonal. The Astro-Physics diagonal I have (and I suspect
a TeleVue diagonal) works fine with the 41mm Pan. So just a caveat on
using the big Pan.
The other caveat on the 41mm, or any 40mm eyepiece for that matter, is
that it would provide a wider than 7mm exit pupil on the NP127,
effectively cutting down the aperture of the scope. In all, I found the
view thru the 31mm Nagler more impressive, with the extra magnification
providing a darker sky and more detail, while the 82° apparent field
means true field of view is not sacrificed. A 55mm Plössl eyepiece
would not be suitable for this scope (too wide an exit pupil) and I
suspect from the brief test I gave it at the SSSP last year, the Pentax
40mm would be good but not as sharp to the edge as the 41mm Pan and
certainly not the 31mm Nagler. I think the Pentaxes are best in 14mm
and shorter focal lengths.
I could not try my 35mm Panoptic as that eyepiece now lives in
Australia, where it gave fabulous views of southern star fields on my
last trip to Oz with the 105mm Astro-Physics Traveler. But it would be
another good low-power choice for the NP127, for less money than the
41mm Pan or 31mm Nagler but with not as wide a field.
The general purpose mid-power eyepiece to get, however, (once again, at
a price!) is the 13mm Ethos. It worked a treat -- almost pinpoint stars
right to the edge beating even Naglers and Panoptics. It's a great
focal length for most objects, with only a high-power 3mm to 6mm needed
for planetary (perhaps a Nagler Zoom if the scope is on a tracking
mount, though the short eye relief and narrow field detract in the
Nagler zooms I feel. I still prefer the long eye relief of a Tele Vue
Radian or Pentax XW for the higher powers).
To test the scope I put it on a Sky-Watcher HEQ5 mount, which was
barely adequate for visual use for this scope, but it is what I had
available on the test night. The NP127 is not particularly heavy for a
5-inch but it needs the EQ6 Pro at least, or a Losmandy G11 or
Celestron GG11, or TV's own alt-az mount perhaps. But a lightweight
equatorial is not suitable for this size scope, even for visual use. So
count that into the cost and portability factor.
My only real criticism of the mechanics of the NP127 is that it does
not have a rotating focuser, so rotating the star diagonal requires
loosening 2 or more screws. The four screws that clamp in the
accessories into the focuser might be nice and secure for imaging but
tend to be awkward for visual use where you are always need to rotate
the diagonal for a comfortable angle -- too many screws to adjust. A
rotating focuser loosened with one large screw would be much better, to
place the focus knobs at the right orientation no matter how the scope
is aimed. The manual 10:1 focuser however was very nice (the test scope
did not have the motorized FocusMate), and in all other respects the
scope is mechanically superb. If I did not already have a 5-inch
apo I suspect I'd go for the NP127 myself.
-- Alan Dyer
April 1, 2008
The
TeleVue 127is can be mounted to a Sky-Watcher EQ6 or other mount with a
Vixen type dovetail mounting system using a 13 inch dovetail plate and
the TeleVue 5" ring set - MRS-5000. Remove the bottom plate and
studs from the tube rings. Attach the tube rings to the 13"
dovetail plate with 3/4" bolts - standard 1/4 x 20 threads.
