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70 AUSTRALIAN SKY & TELESCOPE JULY 2016

1¼-inch Mini Filter Wheel and OAG is a five-position

filter wheel that accepts conventional 1¼-inch filters

in threaded cells. The 150-mm-diameter filter wheel

housing is 28 mm thick and includes female T-threads

on its front and back ports. It comes with its own USB

2.0cableandsoftware.TheOAGisanintegralpartof

the filter wheel and cannot be removed.

TheOAGhasnoindependentadjustmentsto

helpwiththeselectionofguidestarsbeyondasingle

motion that slides the pick-off prism radially within

thefieldofview.Thereisnoside-to-sideadjustmentof

the prism. The OAG has two long locking screws with

convenient knurled knobs. One secures the position

of the pick-off prism while the other locks the

focus position for the autoguider camera.

Initially, this seemed to be a limiting factor

in the OAG design, but locating guide stars

with the Lodestar X2 turned out to be effortless. The

camera’s sensitivity enabled multiple guide star choices

in the field with exposures of one or two seconds.

During my tests, this wasn’t the case most of the

time but every time. Sufficiently bright guide stars

appeared on a very smooth, noise-free background sky

everywhere I pointed, even without applying dark-

frame calibration. Quite simply, the Lodestar X2 was

the best autoguider I’ve ever used.

At the telescope

I tested the Trius-SX814C with a 102-mm f/6.9 William

Optics refractor and at the f/4 Newtonian focus of

my 32-cm classical Cassegrain reflector. I also tried it

attached to a Nikon 300-mm f/2.8 camera lens with a

T-thread-to-Nikon-lens adapter. But due to the limited

backfocus of the lens, I wasn’t able to use the filter

wheel and OAG in this arrangement.

The camera’s compact size, small pixels and

cylindrical shape make it particularly well-suited for

use with fast ‘Hyperstar’ systems now available for

some Schmidt-Cassegrain telescopes.

Imaging with the Trius-SX814C, Lodestar X2

and Mini Filter Wheel with OAG was pleasantly

straightforward when I was shooting with either

telescope. The back focus required for the camera and

OAGwasshallowenoughtoenablemetoreachfocus

on my Newtonian with its low-profile focuser. The

camera reached its set cooling temperature of 20°C

below ambient quickly and was stable in less than five

minutes. Using the camera’s highly sensitive binning

modes was helpful when composing targets and rough

focusing. Fine focus is achieved by observing the full-

width half-maximum readout and moving the focus to

a star’s peak value. A full-resolution image takes about 7

seconds to download.

Once initially configured, the system provided the

most straightforward and quickest setup time of any

deep sky astrophotography configuration I have used.

Even swapping the Trius-SX814C, Lodestar X2 and the

OAG between the small refractor and the Newtonian

filters in threaded

cells. One space

could be blocked

in to be used as

a mechanical

shutter for the

imaging chip.

An integral off-axis guider on the Mini Filter Wheel accepts any of
the company’s current autoguider cameras with a threaded C-mount
interface. The knob at top locks the focus for the guide camera,
while the lower knob secures the pick-off prism’s position.

The Lodestar X2

autoguider includes

internal C-mount

threads, which enable

it to be attached to

the mini filter wheel

OAG, or it can easily be

inserted directly into

any standard 1¼-inch

eyepiece focusers on

most pes.p

Whilenot
anessential
component for
colour cameras,
theMini Filter
Wheel accepts five
1 ¼-inch-format
filters in threaded

AS & T Test Report