ORION TELESCOPES & BINOCULARS 2" Photo-Visual Coma Corrector Instruction Manual

Orion
Corrector for Newtonian Reflectors
The Orion 2" Photo-Visual Coma Corrector for Newtonians
minimizes the coma inherent in fast Newtonian reflectors with
focal ratios from f/3.5 to f/6. Coma appears as flared, comet-
shaped stars and gets progressively worse farther out from
the center of the field. This coma corrector greatly reduces this
effect as well as the effects of field curvature, rendering sharp
stars across the entire field of view or image frame. The 2"
Photo-Visual Coma Corrector can be used for astrophotogra-
phy as well as for visual observing with an eyepiece.
The optics are contained in a 2" barrel, which is threaded into
the upper housing that features an eyepiece holder for 2" eye-
pieces (Figure 1). The eyepiece holder has a non-marring
brass compression ring and two thumbscrews. The bottom end
of the barrel is threaded internally for Orion 2" filters. The third
component is an M48-to-T2 (M42) adapter ring, which is use-
ful when using the Coma Corrector for astrophotography.
For Astrophotography
For astrophotographic use, unthread and set aside the upper
housing. You will need only the optics-containing barrel (Figure
2). The barrel has M48x0.75 male threads at the top. The
M48-to-T2
Adapter
Figure 1. Components of the 2" Photo-Visual Coma Corrector.
A N E M P L O Y E E - O W N E D C O M P A N Y
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INSTRUCTION MANUAL
2" Photo-Visual Coma
®
#52711
2" Eyepiece
holder
2" Barrel
Coma Corrector's back focus is about 75mm (+/- 5mm). So
if using a DSLR—which with a camera-specific T-ring gener-
ally puts the camera sensor about 55mm behind the front of
the T-ring—you'll need a 0.75" (19.1mm) or 20mm extension
ring (sold separately) to achieve the ~75mm backfocus dis-
tance and proper image focus. (In our tests we used an M48
20mm extension ring—available from Orion—and got excel-
lent results.)
The optional M48 extension ring will thread directly on the
male threads at the top of the barrel. Then, if you're using a
DSLR, thread a 48mm T-ring (sold separately) specific to your
camera model onto the male threads of the 20mm extension
ring (Figure 3A).
If you do not have a wide 48mm T-ring for you camera but
instead have a standard T2 (M42) ring, then thread the M48-
to-T2 adapter ring onto the optional extension ring, as in
Figure 3B.
Alternatively, you could attach the M48-T2 adapter ring to the
Coma Corrector barrel's male 48mm threads and use an M42
extension ring and a standard T2-ring (M42) for attachment
M48-to-T2
Adapter
2" Eyepiece
holder
Figure 2. The barrel containing the optics unthreads from the 2"
eyepiece holder (upper housing). For astrophotography the eyepiece
holder is not needed.
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Customer Support: support@telescope.com
2" Barrel
IN 663 06/21