Sky and Telescope - July 2018 - 63
the Windows software failed to present
the required overlays, requiring me to
restart the steps, prolonging the process.
To its credit, the software provides
good on-screen prompts, so there is
no need to consult the included PDF
instruction manual, a good thing as it
doesn't illustrate the steps very clearly.
You ﬁrst need to aim the mount's
polar axis to within at least a few degrees
of the celestial pole to be sure Polaris is
in the PoleMaster's ﬁeld. If it isn't, or, as
I found, if you click on the wrong star
not realizing it isn't Polaris, the next step
of matching the star ﬁeld to the overlay
pattern will never work. In addition,
my little Windows 7 netbook's 1,024 ×
600-pixel-resolution screen required me
to zoom out to see the whole ﬁeld to ﬁnd
Polaris. A laptop with a larger screen
would be helpful, so you don't miss - or
misidentify - Polaris.
To that end, I tried the MacOS version of the software on my 15-inch
retina-screen MacBook Pro. As QHY's
website warns, this will not work - the
stars and overlay never line up. The
solution, while it is mentioned, is not
obvious. Select the PoleMaster app, open
its Get Info window (Command-I) and
check the box "Open in Low Resolution." Once I did that, the PoleMaster
worked just ﬁne on the MacBook.
The process is also promised to work
in the Southern Hemisphere, using
Sigma Octantis as the main alignment
star. However, having aligned many
times using a polar scope Down Under,
I can attest that just aiming a mount's
polar axis at the right area of sky, then
identifying Sigma, can be a real challenge, particularly for those visiting
from the north. I did not test the PoleMaster under southern skies to know
how well it works south of the equator.
I tested the PoleMaster on a SkyWatcher HEQ5 mount. The test unit
was supplied on loan from a local
telescope dealer, All-Star Telescope (allstartelescope.com), which also stocks
the required adapter for my HEQ5. In
addition to the PoleMaster, users also
need to purchase an adapter to attach
it to their particular mount's polar-axis
aperture. Adapters for many popular
mounts are offered by QHYCCD, each
about $30 to $40.
For mounts without a polar-axis aperture, such as a fork mount, one solution
is to purchase a third-party adapter
made by ADM Accessories (admaccessories.com). It allows the PoleMaster
to instead clamp to the telescope tube,
onto either a Vixen dovetail bar or to
a Losmandy D-system plate. I call this
arrangement the off-axis method.
For my testing, I photographed
through a TMB 92-mm refractor with a
focal length of 500 mm, which is usually very forgiving of polar-alignment
p For telescopes that do not have a polar-axis
aperture, adapters are available to attach a
PoleMaster either to another location on the
mount or, as here, to the dovetail mounting bar
on the telescope tube. This is the Vixen V-Series
bracket from ADM.
errors. I shot a series of 30-second
unguided exposures over a 30-minute
interval, then overlaid the ﬁrst and last
frames in Adobe Photoshop to see how
far the star ﬁeld had shifted in each of
several runs over several nights.
On the ﬁrst run, I eyeballed polar
alignment using the polar scope, without taking too much effort to be very
precise, as might be the case for many
astro-imagers in the ﬁeld.
I then ran exposures after aligning
using the PoleMaster on the mount's
polar-axis aperture (what I call the
on-axis method). The next night, after
q Left: Using one of the well-machined adapters offered for popular mounts, the PoleMaster clamps over the polar-scope aperture of a German equatorial mount. Middle: When the PoleMaster is not in place, the aperture remains open to allow using the polar-alignment scope as usual, which is often
necessary for the initial rough alignment. Right: When not in use at all, a supplied metal cover clamps over the adapter, to prevent dust from entering the
polar axis. The camera also includes a screw-on metal cover.
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