Sky and Telescope - October 2015 - 64

S&T Test Report
A few wraps
of Teﬂon tape
applied to the
threaded ﬁtting on the top
of the focuser
allows the eyepiece adapter
to serve as a
ﬁne-thread
helical focuser.

Although the views the scope delivered indicated
good optics, I couldn't resist centering Polaris in the
high-power eyepiece for a quick star test. The scope
produced closely matching intra- and extra-focal images,
conﬁrming the primary mirror of the Vixen is of very
high quality. I was impressed. In short, the scope delivered everything a good 5-inch reﬂector is capable of. I
have no complaints about the quality of the images the
R130Sf presented.

An Imperfect Gem
As rewarding a performer as the Porta II and R130Sf
combination is, I did experience some frustrations that
cropped up particularly when I was observing with
high magniﬁcation. I found the gearing of the rackand-pinion focuser to be a little too crude for the scope's
fast f/5 focal ratio. Often, I'd go from just a little inside
focus, to a little outside, and back again without being
able to nail focus exactly. The solution turned out to be
a minor modiﬁcation. I simply unscrewed the eyepiece
adapter, added a couple wraps of Teﬂon (thread seal)
tape to the threaded ﬁtting on the top of the focuser,
then reattached the adapter. This allowed me to tweak
the focus by unscrewing the eyepiece adapter a turn or
two, transforming it into a ﬁne-thread helical focuser. It
worked very nicely.

The mount generally performed well, with vibrations
dampening out in two or three seconds when the tripod
legs were fully retracted. But if there was any kind of
breeze, the Porta II was prone to quivering, causing the
image in the eyepiece to maddeningly dance around.
Likely this is due to the cantilevered design of the singlearm fork, which oﬀsets the scope's mass about 5 inches
from the center of the mount's azimuth axis.
Another design-related problem crops up when your
target has an altitude greater than roughly 75 degrees.
In those situations, the back end of the OTA can collide
with the tripod legs. You can orient the tube so that it
sits between the legs, but that usually means repositioning the whole telescope - mount and all - and is a
workaround at best. A better solution is the optional SXG
"half-pillar" extension Vixen oﬀers for the Porta II.

Bottom Line
Shortly after I received the scope, S&T Equipment Editor
Sean Walker asked for my initial thoughts. I wrote back:
"I'm impressed by the quality of the optics - the mirror
is very good, as are the eyepieces. On the down side, the
mount is more jiggly than I expected. Not a problem at
low power, but for planetary observing it can be frustrating. The other issue is the plastic focuser, which makes
precise focus at high magniﬁcation a challenge. Overall,
though, I enjoyed using the scope and was pleased with
what Vixen put together for the money."
After spending several additional weeks using the
instrument, my initial impressions stand. Would I
recommend it to a friend as a ﬁrst scope? Yes - but with
the caveat that they get a copy of Terence Dickinson's
NightWatch to serve as a substitute manual. So equipped,
a newbie would ﬁnd the scope rewarding for all kinds
of observing, from sweeping the Milky Way to detailed
close-ups of the Moon and planets. For non-beginners,
the R130Sf and Porta II combination has a lot to oﬀer as a
grab-and-go scope. It's lightweight and quick to set up, yet
with optics good enough to satisfy experienced eyes. ✦
The rear of the telescope tube can collide with the mount's tripod
legs when the scope is aimed at altitudes higher than 75 degrees.
Vixen oﬀers an optional extension pillar to alleviate this problem.

October 2015 sky & telescope

Contributing editor Gary Seronik scans the skies from his
home near Victoria, BC, Canada, and can be contacted
through his website: garyseronik.com.

http://www.garyseronik.com

Sky and Telescope - October 2015

Table of Contents for the Digital Edition of Sky and Telescope - October 2015