T-thread (M42
×
0.75)
adapter or M42
×
1 adapter cause vignetting when used
with cameras equipped with large sensors. Also common coma correctors
(often equipped with T-thread) cause vignetting with this large chip. G3
cameras with 24×36 mm CCD require using of M68
×
1 adapter.
If the mounting standard defines also back focal distance (distance from adapter
front plane to detector), the particular adapter is constructed to preserve defined
distance (for instance T-thread defines back focal distance to 55 mm, but
certain distance is defined also for Pentax (Praktica) thread, for Canon EOS and
Nikon bayonets etc.).
Adapters are attached to the camera body using four M3 (3 mm metric) screws.
These threaded holes are placed on the corners of 44 mm square. Custom
adapters can be made upon request.
Off-Axis Guider Adapter (OAG)
G3 camera can be optionally equipped with Off-Axis Guider Adapter. This
adapter contains flat mirror, tilted by 45° to the optical axis. This mirror reflects
part of the incoming light into guider camera port. The mirror is located far
enough from the optical axis not to block light coming to the main camera
sensor, so the optics must be capable to create large enough field of view to
illuminate the tilted mirror.
Because of the above described reasons the G3-OAG is manufactured with
M68×1 threaded adapter. G3-OAG is compatible with external filter wheels.
Adapter back focal distance is 61.5 mm.
If the OAG has to be used on camera with internal filter wheel, it is necessary
to insert a spacer between OAG and camera head compensating BFD
difference. Similar, but thicker spacer must be used when OAG is mounted to
camera without filter wheel at all.
OAG guider port is compatible with G0 and G1 cameras. It is necessary to
replace the CS/1.25” adapter with short, 10 mm variant in the case of G1
cameras. Because G1 cameras follow CS-mount standard, (BFD 12.5 mm), any
camera following this standard with 10 mm long 1.25” adapter should work
properly with the G3-OAG.
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