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I decided not to image last night due to the light from
the moon. The 12.5" StarMaster was showing above-average detail on
Jupiter and Saturn, so it seemed like a good night to finally test the JMI
NGT-6 telescope at higher powers. The scope had looked very good for wide
field, but I was curious to know how much magnification it could take. The
results of the test were extremely positive.
The NGT-6 is a 6" f/5 (750mm focal length). It is integrated into a
split-ring equatorial mounting, so I can carry scope and mount outside in
one step. Total weight is ~25 pounds, but most of the weight is in the
base so it is a reasonable carry.
I've reviewed the basic mechanics previously; they are very good overall.
The scope points easily and tracks well; it can be balanced with a wide
variety of loads using weights available from JMI. One comes with the
scope, and you can buy weights for both the top and bottom of the scope.
The NGT-6, at f/5 and 6" aperture, sits very low to the ground.
I observed near the edge of our back deck. Being near the edge provided
adequate stability for the powers used. I simply sat down on the deck next
to the scope to observe. JMI sells a tripod for the scope for viewing
while standing up. <g>
The scope retained perfect collimation from the previous outing.
I centered with a Takahashi 30mm LE eyepiece (25x). The view was bright
and sharp to the edge of the 52-degree AFOV. No coma noticed. Contrast was
good even with Jupiter in the field. The over-used phrase
"refractor-like" applies here; the sky is black, and the stars
are pinpoints. The moon was out last night, creating significant sky glow,
but I know from previous tests under dark skies that even with the wide
field of view, the view has excellent contrast. The contrast is so good
that, on any given night, you will get about as good a view as you can
from a reflector. The secondary is 1.3", yielding a small 22%
obstruction by diameter. This compares favorably with Mak-Newts of similar
aperture.
Next up: the Tak 12.5mm eyepiece (60x). The view was still razor sharp,
with Jupiter's two equatorial bands very evident, and some detail visible
at the edges of the bands. The slight darkening of the polar areas was
evident even at this low power, along with hints of another band.
Next up: the Tak 4mm HI Ortho (188x). The view of Jupiter was stunning at
this power. Detail was evident within the EQ bands; several additional
bands were visible; the GRS was at the edge but coming into view very
crisp. The darker center was evident. The darker areas near the poles were
distinct. A white chunk into the EQ band opposite the GRS's band was very
obvious. The detail on Jupiter was the best I've ever seen from a 6"
reflector. And the Jupiter details beat the pants off of my former
10" Dob, believe it or not, which never showed much beyond two fuzzy
EQ belts.
There was more detail visible on Jupiter with the StarMaster 12.5".
However, the seeing only supported about 250x with the StarMaster, so it
wasn't a whole lot more. <g> Some of the smaller details hinted at
in the NGT-6 were clearer in the StarMaster. But the NGT-6 was apparently
less affected by the seeing, which gave it the advantage in contrast most
of the time; when the seeing settled down, detail jumped out in the larger
scope, as it should.
Saturn was already low by the time I did the planetary viewing (around 2am
local time, pacific), so it wasn't a very good test due to atmospheric
refraction (red and blue fringes) and worse seeing conditions.
Next step was a star test. I star tested at 188x with the 4mm, and at 125x
(Tak 12.5mm plus TV 2x Barlow). The 188x test explained why the Jupiter
details were so impressive. The diffraction rings were extremely thin and
well-defined, perfectly circular, and virtually identical inside and
outside of focus. Other than my StarMaster, this is the best star test
I've seen on a reflector. The mirrors are made in Russia, and JMI says
they are better than the mirrors commonly sold on 6" reflectors; I
believe them. <g>
Bottom line: between the mirror quality, the unique design, and the fact
that you get a compact scope plus mount for $999, the NGT-6 is a clear
winner. You do need to determine if you'll be comfortable with such a
short scope, although this turns into a major plus for young kids. It's
about as easy to point as a Dob, but much more flexible because of the
built-in motor drive.
Like any EQ Newt, you'll want to position the eyepiece for your intended
viewing for the night. You can rotate the eyepiece location, but you have
to loosen three screws on the mirror base to do it, so it's not a casual
thing, but it's not bad.
This scope is a legitimate and cost-effective alternative to a 6" Mak
Newt for casual viewing. It has superb optics, a small obstruction, and
scope and mount are one unit.
For imaging, you will need to replace the stock focuser with a
lower-profile unit. The ST-237 is a good match for this scope, and any of
the light Starlight Xpress cameras should also work well.
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