Baader Planetarium M54 Extension Tube – 7.5 mm
- Provides 7.5 mm of Fixed Extension
- M54 x 0.75 Male and Female Threads
- Essential for Correcting Back Focus
- Matte Black Interior to Reduce Reflections
- Maintains Rigidity in the Imaging Train
This M54 Extension Tube provides a fixed, non-flexing 7.5 mm of spacing, a critical component for achieving the precise back focus required by field flatteners, coma correctors, and focal reducers. It is designed for modern imaging trains that utilize the large M54 standard to connect full-frame cameras and large-format accessories without vignetting.
Achieving sharp, coma-free stars from corner to corner depends entirely on setting the exact distance between your corrector lens and sensor plane. This M54 extension tube adds exactly 7.5 mm to your imaging train, allowing you to precisely dial in the required back focus. Using a fixed-length tube provides a more rigid and tilt-free connection than many variable extension systems, which is crucial for maintaining optical alignment.
Its primary purpose is to set the correct back focus distance in an astrophotography imaging train. Most focal reducers and field flatteners require a specific spacing to the camera sensor (typically 55 mm), and this 7.5 mm tube is used to fill a small, precise gap to achieve that target distance.
You need to calculate your current back focus and compare it to what your corrector requires. Add up the optical path length of all components behind your corrector (e.g., filter wheel, off-axis guider, camera flange distance). If the total is, for example, 47.5 mm and your corrector needs 55 mm, this 7.5 mm extension tube is the perfect component to make up the difference.
Yes, you can stack multiple extension tubes. However, for maximum rigidity and to minimize the potential for sensor tilt, it is always best to use a single extension tube of the correct length whenever possible. Stacking several small spacers can introduce slight misalignments.
A fixed extension tube like this one offers superior rigidity. Variable spacers, while flexible, can sometimes introduce a small amount of tilt or flexure into the imaging train, especially with heavier cameras. A fixed tube provides a solid, stable, and repeatable connection, which is critical for consistent, sharp results.
No. The M54 thread standard is specifically designed to provide a large, clear aperture to fully illuminate full-frame sensors (36x24 mm) without vignetting. This extension tube maintains that clear aperture throughout its length, ensuring the light cone from your corrector reaches the entire sensor.
Yes, absolutely. Many focal reducers designed for SCTs, such as the Celestron f/7 reducer for EdgeHD models, use M54 threads and require precise back focus. This extension tube is an ideal component for building out the correct spacing between the reducer and your camera.