What is the main purpose of the Svbony SV109 Variable Extension Tube?
The primary purpose of the Svbony SV109 is to precisely set the distance between a field flattener or focal reducer and the camera sensor. It provides a 24mm to 35mm adjustable range to achieve the exact back focus required for a flat imaging field, eliminating the need for multiple fixed-length spacers.
How do I adjust the length of the SV109 extension tube?
You adjust the length by twisting the two barrels of the extender. This helical mechanism provides smooth, continuous adjustment across its 11mm range. Once you find the correct spacing, the friction holds its position securely for your imaging session.
Will the Svbony SV109 work with my 2-inch filters and accessories?
Yes. The SV109 uses the standard M48x0.75 thread, which is the common thread size for 2-inch filters, filter wheels, off-axis guiders, and camera adapters designed for full-frame or large-sensor astronomical imaging.
Why does the SV109 have internal threads?
The internal threading acts as an effective light baffle. This design scatters and absorbs any stray light that enters the tube, preventing it from causing internal reflections that can reduce contrast and introduce artifacts in your astrophotos.
My reducer needs 55mm of back focus. Can I use the SV109 to get there from my camera's 20mm flange distance?
Yes, this is an ideal use case. If you need 35mm of spacing (55mm total minus your camera's 20mm), you can set the SV109 to its maximum extension of 35mm to achieve the correct distance. This single accessory provides the exact spacing required without needing any other parts.
I'm imaging the Andromeda Galaxy (M31) with a small refractor and a flattener. Why is the SV109 better than fixed rings?
When imaging a large target like the Andromeda Galaxy (M31), achieving a perfectly flat field is essential. The SV109 allows for micro-adjustments in spacing (e.g., setting it to 28.5mm) that are impossible with fixed rings. This fine control lets you perfectly tune the flattener's distance for your specific telescope, ensuring sharp stars across the entire frame.
