What is the primary use for the SVBONY SV109 extension tube?
The SVBONY SV109 is used to add a precise and adjustable amount of distance in an M42/T2-threaded optical train. Its primary purpose is to achieve the critical back focus distance required by field flatteners, coma correctors, and focal reducers for optimal astrophotography results.
How do I set a specific distance, like 30mm, with the SV109?
The SV109 adjusts by twisting the two barrels. To set a specific distance, you can use a digital caliper to measure the extension as you adjust it. Once the desired length is achieved, the friction of the mechanism holds the position securely.
Can I use the SV109 to achieve the standard 55mm back focus for my DSLR and coma corrector?
Yes, the SV109 is a key component for achieving 55mm. A typical DSLR with a T-ring has about 55mm of back focus on its own. If you add a filter wheel or off-axis guider (which might use 20-30mm), the SV109's 24-35mm range is perfect for making up the remaining distance precisely.
Will the M42 threads on the SV109 connect to my Celestron T-adapter or ZWO camera?
Yes. The SV109 uses the astronomical standard M42*0.75 thread, commonly known as the T2-thread. This is the same thread used on virtually all Celestron T-adapters, ZWO and QHY astronomy cameras, and most filter wheels and off-axis guiders.
Is the SVBONY SV109 strong enough for a heavy astronomy camera?
The SVBONY SV109 features all-metal construction. It is designed to be rigid and can securely hold common cooled astronomy cameras and DSLRs without flexure, ensuring your imaging train remains perfectly aligned.
Why is the inside of the SV109 extension tube black?
The black anodized finish on both the interior and exterior surfaces minimizes stray light reflections. This is critical for maintaining high contrast in your images by preventing internal reflections from reaching the camera sensor.
