Sky and Telescope - August 2017 - 59

Collimation requires some kind of
tool, which can be as simple as a reﬂective cap with a hole in the center or
as high-tech as a laser. It also requires
the center of the primary mirror to be
marked in some way, preferably with a
white donut.
The Zhumell Z130, like the other
130-mm tabletop Dobs I've looked at in
recent years, is shipped with a centerspotted mirror. That's a great convenience for experienced astronomers and
a huge beneﬁt for beginners. While it's
not really very hard to remove a mirror,
center-spot it, and re-install it, the process is intimidating for beginners. However, the Z130 does not include a simple
collimation tool. That's a non-issue
for an experienced astronomer, who is
likely to own at least one collimation
tool already, but purchasing a collimation tool is an added inconvenience for
a beginner who buys a Z130.
The primary mirror of my Z130
was fairly badly out of collimation
when it arrived, and collimating it
proved surprisingly complicated. Most
reﬂectors have large thumbscrews to
adjust the primary mirror's tilt. With
the Z130, you ﬁrst need to remove a
thin metal plate from the back of the
scope, which serves no obvious purpose
besides blocking access to the collimation screws and preventing the mirror
from cooling down as fast as it might.

p Collimating the main mirror requires removing a metal plate, then loosening three locking
screws with an Allen wrench and turning the collimation screws with a Phillips-head screwdriver.

Once the plate was removed, I discovered two sets of screws were required for
adjusting the primary mirror. An Allen
wrench (not supplied with the scope) is
needed to loosen the 3 locking screws,
along with a Phillips-head screwdriver
to turn the collimation screws. Fortunately, the telescope has remained in
perfect collimation ever since the ﬁrst
time I adjusted it.

The telescope is shipped with two
Kellner eyepieces, with focal lengths of
25 and 10 mm, yielding 26× and 65×
respectively. Those are excellent magniﬁcations for deep-sky observing, and
the 10-mm eyepiece together with a 2×
Barlow lens shows ﬁne planetary images
at 130×. But the telescope is capable of
much more. A 32-mm Plössl or 24-mm
wide-ﬁeld eyepiece yields low-power
images that are signiﬁcantly wider and
somewhat sharper at the edges than the
25-mm Kellner. And I found 162× using
my own 4-mm eyepiece just about ideal
for planetary observing.
The plastic focuser included with
the Z130 is rather coarse, so focusing at
such high magniﬁcations requires a little
ﬁddling. Fortunately, the heavy-duty
mount is very stable, so vibrations from
twisting the focuser knob die away rapidly. The optical tube works even better
t t The optical tube is held in rings that attach to the mount with a Vixen-style dovetail
plate. That makes it easy to attach to most
commercial telescope mounts.
t The red-dot finder is simple but effective.
The plastic focuser, however, is only marginally
adequate at high magnifications.
s k y a n d t e l e s c o p e .c o m

* AUGUST 2017

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Sky and Telescope - August 2017

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