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PrimaLuceLab OnAxisLock2 50.8mm Visual Back for ESATTO 2" or ARCO 2" (PL8410015)
The PrimaLuceLab OnAxisLock2 (PL8410015) provides a rigid, perfectly centered connection for your 50.8mm (2") accessories to any ESATTO 2" focuser or ARCO 2" rotator via its native M56 thread. Its double compression ring keeps the optical axis centered, even with heavy cameras, and the visual back has an optical thickness of 26mm.
OnAxisLock2: A Tilt-Free Lock for 50.8mm Accessories
Unlike traditional set-screw locking systems, the OnAxisLock2 uses a double compression ring that applies uniform pressure around the entire barrel of your 2" eyepiece or camera nose: no scratches, no flexure, no off-axis tilt. A simple twist of the knurled outer ring, operable even with gloves on, engages the lock, holding heavy diagonals and cameras securely without leaving scratches or pressure marks.
M56 Thread for ESATTO 2" and ARCO 2" Integration
This OnAxisLock2 visual back is engineered specifically for the PrimaLuceLab ecosystem, threading directly onto the M56 output of the ESATTO 2" robotic focuser or the ARCO 2" robotic rotator. This direct, adapter-free connection creates a solid, repeatable mechanical interface that is critical for maintaining alignment in a demanding imaging train.
OnAxisLock2 vs. Standard Visual Back: 26mm vs. 12.5mm Optical Path
PrimaLuceLab offers two visual back options for the ESATTO 2" and ARCO 2", each with a distinct trade-off. Your choice depends mainly on your back-focus budget.
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OnAxisLock2 (PL8410015): Offers superior axial alignment with its double compression ring and single-twist lock. It consumes 26mm of optical path, making it ideal for imaging setups where perfect sensor alignment is non-negotiable and sufficient back focus is available.
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Standard Visual Back (PL8410001): Uses a traditional brass compression ring with three locking screws and consumes only 12.5mm of optical path. This is the better choice when back focus is limited.
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How does the OnAxisLock2 improve imaging with an ESATTO 2" focuser and a heavy camera?
A set screw applies all clamping force at one point on the barrel, and under load this causes micro-flexures that shift the focal plane and tilt the sensor. The OnAxisLock2 grips the camera's 2" nose with uniform 360° pressure, so the camera stays centered on the optical axis.
Why choose the OnAxisLock2 over the standard PrimaLuceLab 2" visual back (PL8410001)?
Choose the OnAxisLock2 (PL8410015) for maximum security and alignment. Its double compression ring is superior for heavy cameras and keeps a centered optical axis. Choose the standard visual back (PL8410001) only if you have a critical back-focus limitation, as it uses 12.5mm of optical path compared to the OnAxisLock2's 26mm.
Will the 26mm optical thickness of the OnAxisLock2 affect my ability to reach focus?
Possibly. The 26mm optical thickness consumes back focus. Before purchasing, you should verify that your telescope and imaging train have at least 26mm of available back focus to spare.
Is the OnAxisLock2 secure enough for a large 2" diagonal and heavy eyepiece on my SCT with an ARCO 2" rotator?
Yes. Heavy 2" eyepieces and mirror diagonals connect without wobble, because the double compression ring grips the barrel with uniform pressure instead of a single set screw. On the ARCO 2", the visual back screws directly onto its M56 thread.
Can I use the OnAxisLock2 with accessories other than eyepieces?
Absolutely. The OnAxisLock2 is ideal for any accessory with a standard 50.8mm (2") barrel, including:
- Mirror and prism diagonals
- Cooled astronomy cameras
- DSLR and mirrorless camera nosepieces
- Filter wheels and other photographic accessories with a 2" nose
Does the OnAxisLock2 fit any focuser other than the ESATTO 2" or ARCO 2"?
It screws onto the M56 thread of the PrimaLuceLab ESATTO 2" focuser and ARCO 2" rotator. Use on other focusers is not documented.
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| Brand |
PrimaLuceLab |
| Model |
PL8410015 |
| Type |
50.8mm (2") visual back |
| Telescope Side Connection |
M56 thread (for ESATTO 2" or ARCO 2") |
| Accessory Side Connection |
Accepts 50.8mm (2") accessories |
| Locking Mechanism |
Double compression ring |
| Optical Thickness |
26mm |
| EAN |
8059020775162 |
| Warranty |
1 year |
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OnAxisLock2 50.8mm Visual Back
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PrimaLuceLab 1-Year Warranty
