ORION TELESCOPES & BINOCULARS 2" Photo-Visual Coma Corrector User manual

Orion®2" Photo-Visual Coma
Corrector for Newtonian Reflectors
#52711
IN 663 06/21
INSTRUCTION MANUAL
Corporate Offices: 89 Hangar Way, Watsonville CA 95076 - USA
Toll Free USA & Canada: [phone]
International: [phone]
Customer Support: [email protected]
Copyright © 2021 Orion Telescopes & Binoculars.All Rights Reserved. No part of this product instruction or any of its contents
may be reproduced, copied, modied or adapted, without the prior written consent of Orion Telescopes & Binoculars.
AN EMPLOYEE-OWNED COMPANY
The Orion 2" Photo-Visual Coma Corrector for Newtonians
minimizes the coma inherent in fast Newtonian reectors with
focal ratios from f/3.5 to f/6. Coma appears as ared, comet-
shaped stars and gets progressively worse farther out from
the center of the eld. This coma corrector greatly reduces this
effect as well as the effects of eld curvature, rendering sharp
stars across the entire eld 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" lters. 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
Coma Corrector’s back focus is about 75mm (+/- 5mm). So
if using a DSLR—which with a camera-specic 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) specic 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
Figure 1. Components of the 2" Photo-Visual Coma Corrector.
Figure 2. The barrel containing the optics unthreads from the 2"
eyepiece holder (upper housing). For astrophotography the eyepiece
holder is not needed.
2" Eyepiece
holder
2" Eyepiece
holder
M48-to-T2
Adapter
M48-to-T2
Adapter
2" Barrel
2" Barrel

2
Corporate Offices: 89 Hangar Way, Watsonville CA 95076 - USA
Toll Free USA & Canada: [phone]
International: [phone]
Customer Support: [email protected]
Copyright © 2021 Orion Telescopes & Binoculars.All Rights Reserved. No part of this product instruction or any of its contents
may be reproduced, copied, modied or adapted, without the prior written consent of Orion Telescopes & Binoculars.
AN EMPLOYEE-OWNED COMPANY
One-Year Limited Warranty
This Orion product is warranted against defects in materials or workmanship for a period of one year from the date
of purchase. This warranty is for the benet of the original retail purchaser only. During this warranty period Orion
Telescopes & Binoculars will repair or replace, at Orion’s option, any warranted instrument that proves to be defective,
provided it is returned postage paid. Proof of purchase (such as a copy of the original receipt) is required. This war-
ranty is only valid in the country of purchase.
This warranty does not apply if, in Orion’s judgment, the instrument has been abused, mishandled, or modied, nor
does it apply to normal wear and tear. This warranty gives you specic legal rights. It is not intended to remove or
restrict your other legal rights under applicable local consumer law; your state or national statutory consumer rights
governing the sale of consumer goods remain fully applicable.
For further warranty information, please visit www.OrionTelescopes.com/warranty.
to your camera. Note that adding the M48-to-T2 adapter ring
adds 6.1mm of length to the barrel, so the spacing require-
ment to achieve the ~75mm backfocus distance will be less,
accordingly.
For astronomical CCD or CMOS cameras additional extension
will be required to reach the 75mm backfocus distance. The
amount of extension needed can be determined by factoring
in your camera’s sensor position relative to its front ange.
Check your astronomical camera to determine the thread size
needed for attachment of the Coma Corrector. You will have to
remove the camera’s nosepiece, which will reveal the threads,
which for many cameras are 42mm female threads. If that’s the
case you will need to use the M48-to-T2 adapter ring to attach
the Coma Corrector barrel and any additional extension rings
to the camera.
For Visual Use
For visual use of the 2" Photo-Visual Coma Corrector some
additional extension may be required for certain eyepieces.
Some users report that adding a 0.75" (19.1mm) extension
ring (M48) between the upper housing and optical nose-
piece allowed perfect focus with their wide-eld eyepieces
(Figure 4). Some eyepieces may not require any additional
spacing for the Coma Corrector, or may just need to be backed
out a bit from the Coma Corrector’s eyepiece holder to achieve
the correction needed.
Figure 3. A) For astrophotography with a DSLR, a 20mm M48
extension ring and M48 T-ring for your camera model are needed
(both sold separately). B) For DSLR use with a standard T-ring
(M42), the included M48-to-T2 adapter ring is needed, as it would
be with many astronomical CCD and CMOS cameras equipped with
a female 42mm mounting thread.
Figure 4. For visual use, some additional spacing in the form of
M48 extension rings may be necessary to achieve proper correction
and focus.
A
B
Barrel
Barrel
20mm extension ring (M48) Extension ring(s) M48
Extension
ring (M48)
T-ring (48mm)
T-ring (42mm)
M48-to-T2 Adapter