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Adapter 3.25" Female to M68 Male for Celestron C11 & C14 SCTs
This adapter converts the large 3.25-inch female thread on Celestron C11, C14, and EdgeHD telescopes to a standard male M68 x 1.0mm thread, consuming only 2.9mm of backfocus in the process. It is the essential first link for building a rigid, wide-aperture imaging train on Celestron's largest Schmidt-Cassegrain telescopes.
M68 Male Thread for C11/C14 3.25" Visual Backs
Modern correctors, off-axis guiders, and large filter wheels often rely on the M68 thread standard to prevent vignetting with full-frame sensors. This adapter directly attaches to the 3.25" visual back of large Celestron SCTs, providing the secure M68 connection point needed to attach these high-end accessories without introducing flexure.
A Minimal 2.9mm of Backfocus Consumption
Backfocus is a critical and limited resource, especially when using reducers or flatteners. This adapter is engineered to be as thin as possible, using only 2.9mm of the optical path. This minimal light path consumption leaves maximum room for complex imaging trains that include filter wheels, rotators, and off-axis guiders.
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Which telescopes is this 3.25" to M68 adapter compatible with?
This adapter is designed specifically for Celestron Schmidt-Cassegrain telescopes that feature the large 3.25-inch threaded visual back. This includes most Celestron C11, C14, and all EdgeHD 1100 and 1400 models.
How much backfocus does the 3.25" to M68 adapter use?
The adapter consumes precisely 2.9mm of backfocus. Its slim profile is designed to preserve as much of your telescope's available backfocus as possible for other imaging accessories.
What is the thread on the accessory side of this adapter?
The male thread for attaching your accessories is an M68 thread with a 1.0mm pitch (M68x1). This is a common standard for full-frame correctors, reducers, and other large-format imaging components.
Will this 3.25" adapter work on a Celestron C8 or C9.25?
No. Standard Celestron C8 and C9.25 telescopes use a smaller 2-inch SCT thread on their visual backs. This adapter is only for the larger 3.25-inch thread found on C11 and C14 models.
Can I use this M68 adapter to attach my M48 filter wheel to a C14 EdgeHD?
Yes, but you will need an additional M68 to M48 step-down adapter. This 3.25" adapter provides the initial M68 connection point on your C14 EdgeHD, from which you can adapt down to other thread sizes like M54 or M48 for your specific equipment.
Why would I choose an M68 connection over a standard 2-inch nosepiece for my C11?
A threaded M68 connection is significantly more rigid and secure than a 2-inch nosepiece held by thumbscrews. For astrophotography with heavy cameras and accessory trains, a fully threaded connection like the one this adapter provides prevents tilt and flexure that can ruin an exposure.
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| Telescope Side Thread |
3.25" Female |
| Accessory Side Thread |
M68 Male (1.0mm Pitch) |
| Backfocus Consumption |
2.9mm |
| Compatibility |
Celestron C11, C14, EdgeHD 1100, EdgeHD 1400 |
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Adapter 3.25" Female to M68 Male
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Pegasus Astro 2-Year Warranty
