Orion 8671 Instruction Manual
Orion® 3" Field Flattener for
EON 115 & 130 f/7 Triplet
Refractors
#86 71
INSTRUCTION MANUAL
Providing Exceptional Consumer Optical Products Since 1975
IN 560 Rev. A 10/15
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This large-format field flattener, designed for photography with the Orion EON
115mm and 130mm f/7 triplet refractors, flattens the focal plane for astro-imaging
without affecting the focal length of the telescope. When imaging with a CCD or
DSLR camera, the far edges of the field of view will appear sharper when using
the field flattener with your EON telescope.
Connection to Telescope
The 3" Field Flattener threads directly onto the 3" dual-speed Crayford focuser of
the Orion EON 115 and 130 f/7 triplet refractors, for a rock-solid connection. The
Field Flattener has M92x1.0 male threads, which mate with the female threads
on the focuser. First remove the accessory collar from the focuser by turning the
knurled ring counterclockwise, as shown in Figure 1. Then screw the flattener
into the focuser.
The optimal backfocus distance (distance from the rear flange of the flattener,
excluding the M48 thread, to the camera sensor) is 51.5mm. However the flattener is known to provide sharp images at up to 5mm either side of this distance.
Connection to a DSLR Camera
The 3" Field Flattener features M48x0.75 threads on the camera side, wider than
the typical T-mount (M42), to minimize vignetting and provide better illumination of full-frame camera sensors. Thus, for DSLRs you will need an M48 DSLR
adapter – a wider version of the standard T-ring.
Connection to a CCD Camera
Most CCD cameras require less backfocus than a DSLR camera. That means
you will need to add spacing as needed to fill the 51.5mm of required distance
to the Field Flattener. M48 (2") spacers are available from third party vendors.
Figure 1. To install the field flattener, A) remove the accessory collar as shown, then B)
thread on the field flattener until tight.
Accessory collar knurled ring
A
B
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