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Pegasus Astro Adapter M66 Female to M54 Male (For SW Esprit 100)
This Pegasus Astro adapter is the essential component for connecting your Sky-Watcher Esprit 100 flattener to the M54 standard, providing exactly 15.8mm of optical path length. It converts the Esprit's native M66 female thread (1.0mm pitch) to a male M54 thread with a standard 0.75mm pitch, allowing direct integration with modern filter wheels, off-axis guiders, and cameras.
The 15.8mm Bridge from Esprit 100 to M54 Accessories
The Sky-Watcher Esprit 100 requires a specific backfocus distance for a flat field, and this adapter is machined to provide a precise 15.8mm contribution to that optical train. It solves the critical connection problem between the telescope's M66 flattener output and the widely adopted M54x0.75mm thread standard common on accessories like the Pegasus Astro Indigo series.
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Female Thread (Telescope Side): M66 with a 1.0mm pitch, designed to securely attach to the Esprit 100's field flattener.
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Male Thread (Camera Side): M54 with a 0.75mm pitch, providing a rigid connection point for your imaging equipment.
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Fixed Spacing: The 15.8mm length is non-adjustable, ensuring repeatable and accurate spacing every time you assemble your imaging train.
Example Imaging Train: Achieving 63mm Backfocus
This adapter is a key part of building a fully-featured imaging train with the Esprit 100. When combined with other standard components, it allows you to achieve the correct total backfocus distance for sharp stars across the frame. For example, a complete setup can be assembled to hit a 63mm backfocus target.
A confirmed, optimal imaging train consists of the Sky-Watcher Esprit 100, this 15.8mm M66-to-M54 adapter, a Pegasus Astro Indigo OAG, a Pegasus Astro Indigo Filter Wheel, and a QHY268M camera. This specific combination results in the required 63mm backfocus for the Esprit 100 system.
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What is the primary function of this Pegasus M66 to M54 adapter?
Its primary function is to connect the M66 threaded field flattener of a Sky-Watcher Esprit 100 telescope to standard M54 threaded astrophotography accessories. It also provides a fixed optical path length of 15.8mm to help achieve the telescope's required backfocus.
How much backfocus does this Esprit 100 adapter add to the imaging train?
The adapter adds exactly 15.8mm of backfocus distance. This value is critical for calculating the total spacing needed for your specific camera and accessories.
Are the threads on the Pegasus adapter standard?
Yes, the male M54 thread uses the standard 0.75mm pitch common to most astronomy equipment. The female M66 thread uses a 1.0mm pitch specifically to match the output of the Sky-Watcher Esprit 100's flattener.
Can I use this adapter with a telescope other than the Sky-Watcher Esprit 100?
This adapter is specifically designed for the Sky-Watcher Esprit 100. While it might physically thread onto another telescope with an M66x1.0mm output, its 15.8mm length is optimized for the Esprit's backfocus requirement and may not be correct for other optical systems.
How do I build a complete imaging train for my Esprit 100 using this Pegasus adapter?
A proven combination for the Esprit 100 that achieves the optimal 63mm backfocus is: Esprit 100 Flattener → this M66-to-M54 Adapter → Pegasus Indigo OAG → Pegasus Indigo Filter Wheel → QHY268M Camera. This setup provides a complete, rigid imaging solution.
Will this adapter work with my ZWO camera on an Esprit 100?
Yes, as long as your ZWO camera and any accessories (like a filter wheel or OAG) can connect via the standard M54x0.75mm male thread on this adapter. You will need to calculate your total backfocus to ensure you meet the Esprit 100's requirement, using this adapter's 15.8mm contribution as a starting point.
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| Telescope Side Thread |
M66 Female (1.0mm Pitch) |
| Accessory Side Thread |
M54 Male (0.75mm Pitch) |
| Backfocus Contribution |
15.8mm |
| Compatibility |
Connects SW Esprit 100 Flattener with M54 accessories |
| Example Imaging Train |
SW Esprit 100 + Adapter + Indigo OAG + Indigo Filter Wheel + QHY268M = 63mm |
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Adapter M66 Female to M54 Male (For SW Esprit 100)
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Pegasus Astro 2-Year Warranty
