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.7x Reducer Lens – EdgeHD 800
Instruction Manual – Model #94242
Your .7x reducer lens makes your EdgeHD 800 telescope one
full F-Stop faster than at f/10. Photographically this will enable you
to reduce your exposure times by one-half and still capture the
same amount of light, while providing a 43% wider fi eld of view.
Telescope Model f/2.1 Confi guration .7x Reducer Lens Standard f/10 Confi guration
8” 425 mm (17”) 1422 mm (56”) 2032 mm (80”)
Focal lengths for the EdgeHD 800 in its native format (f/10), with the .7x Reducer Lens and with optional f/2 lens assembly.
Attaching the Reducer
1. Remove the visual back from the rear of the telescope.
2. The focal reducer threads directly onto the rear adapter
plate (see Figure 1) of your EdgeHD telescope.
3. Attach your T-Adapter (#93644, sold separately) onto the
rear threads of the focal reducer and remove its threaded
extension (see Figure 2).
EdgeHD 8” – Optimum Back Focus Distance
Remove Visual Back
Camera Spacing
The optimum photographic back focus of the EdgeHD 8” is
133 mm at f/10, and 105 mm when used with the Reducer
Lens at f/7. The optional T-Adapter for EdgeHD 8” (#93644)
works in both confi gurations when used with a DSLR,
Nightscape, or any other camera with 55 mm back focus.
When imaging with the Reducer lens, remove the threaded
extension of the T-adapter to reach optimum back focus.
For best performance, it is highly recommended that you
position your camera as close to the recommended optimal
spacing as possible. It is best to maintain optimal spacing
to within 1-3 mm depending on the size of your imaging
sensor. As your imaging chip gets larger (farther off-axis),
maintaining optimal spacing becomes more critical. Being
inside of focus (too short) tends to affect the outermost edge
of the fi eld of view when using a relatively large sensor
(17 mm or greater). Being outside of focus (too long) tends
to produce elongated star images towards the edge and
could run the risk of running out of focus travel on your
EdgeHD optical tube. In general it is better to be slightly
inside of focus than outside of focus.
Reducer Lens
Adapter
Plate
Figure 1 – Optimum Spacing for EdgeHD 8”
T-Adapter Extension
Figure 2 – T-adapter and extension
T-Adapter
4.13”
105 mm
T-Ring
Camera
Focal
Plane
Warranty: Two year limited warranty.
For complete warranty details contact Celestron or visit:
Celestron LLC • 2835 Columbia Street • Torrance, CA 90503
Phone: 800.421.9649 • Fax: 310.212.5835
©2013 Celestron • All rights reserved. #94242-INST 03-13
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