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Baader Expanding Ring - T-2(F)/M48x0.75(M)
The Baader T-2 to M48 Expanding Ring adapts the universal female T-2 (M42x0.75) thread to the larger male M48x0.75 standard, creating a secure, full-aperture connection to 2-inch accessories. On the telescope side it screws onto a male T-2 thread; on the camera side its male M48 thread takes 2-inch filters and other parts with a female M48 thread.
Bridge Your T-2 and M48 Imaging Train
In many imaging setups, the camera or off-axis guider uses the M42-based T-2 thread standard, while larger format correctors and filter wheels have adopted the M48 thread to prevent vignetting on larger sensors. This expanding ring acts as the crucial bridge, allowing you to step up the thread size early in the imaging train to maintain the widest possible light cone.
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Eliminate Bottlenecks: By converting from T-2 to M48, you ensure your optical train is not restricted by the smaller M42 diameter, which is especially important for full-frame or large APS-C sensors.
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Connect to 2" Filters: Baader says the male M48 thread fits all 2" filters.
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Universal Compatibility: Baader's precise machining ensures a perfect fit with accessories from any manufacturer that adheres to the T-2 and M48 thread standards.
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What is the primary purpose of the Baader T-2 to M48 Expanding Ring?
Its main purpose is to screw onto a male T-2 (M42x0.75) thread on the telescope side and present a larger male M48x0.75 thread on the camera side, which fits all 2-inch filters and other parts with a female M48 thread.
Will this Baader adapter add significant length to my imaging train?
While any adapter adds some optical path length, expanding rings like this are designed to be as thin as possible. Baader Planetarium engineers these components to contribute minimal back focus, ensuring you can reach focus and maintain the correct spacing for your optical correctors.
Does this adapter have threads for 1.25" filters?
No. This is strictly a thread converter. It does not have internal threads for mounting filters. Its purpose is to allow connection to accessories that hold 2-inch (M48) filters.
Why would I expand to M48 instead of staying with T-2 threads for my full-frame camera?
Using T-2 (M42) threads with a full-frame sensor can cause significant vignetting, where the corners of the image are darkened because the light path is physically constricted. Stepping up to the larger M48 diameter as close to the sensor as possible provides a wider, un-obstructed opening for the light cone, resulting in more even illumination across the entire frame.
Is the male M48 thread on this Baader adapter long enough to attach multiple accessories?
The male M48 thread is a standard length designed to make a secure connection with one female-threaded accessory. It is not an extension tube and is not intended for stacking multiple components on its male thread.
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| Input Thread (Female) |
T-2 (M42x0.75) |
| Output Thread (Male) |
M48x0.75 |
| Type |
Expanding Ring / Thread Adapter |
| Net weight (kg) |
0.01 |
| Inner Diameter / Clear Aperture (mm) |
41 |
| Outer Diameter |
50.5 |
| Optical length (mm) |
2.5 |
| T-2 Part # |
29 |
| Outer Connection (eyepiece/-camera-sided) |
M48 |
| Adapters Family |
T-2 System, M48 System |
| Telescope-side connection |
M42x0.75 Female (T-2) |
| Camera-side connection |
M48x0.75 Male |
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Baader Expanding Ring - T-2(F)/M48x0.75(M)
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Baader Planetarium Warranty
