What is the primary use for the William Optics M48 to M42 Adapter?
Its primary function is to connect an imaging train component with female M48 threads (like a field flattener or coma corrector) to a camera, T-ring, or other accessory that has male M42 threads. It adds only 5.3 mm to the total optical path.
I have a William Optics flattener with M48 threads and need to connect my DSLR with an M42 T-ring. Is the WO-YE-M48-42 the right adapter?
Yes, this is the exact application for this adapter. It will step down the M48 thread on your flattener to the M42 thread on your T-ring, consuming just 5.3 mm of back focus in the process.
How does the 5.3 mm optical length of this adapter affect my back focus calculation?
You must subtract the 5.3 mm optical length from your total available back focus. For example, if your flattener requires 55 mm of back focus, installing this adapter means you now have 49.7 mm remaining for any other components in your imaging train.
Is the William Optics M48 to M42 Adapter the same as a 2" filter?
No. While it uses the same M48 thread pitch as a standard 2" filter, this adapter is a mechanical converter, not an optical element. It changes the thread type from M48 to M42 and does not alter the light passing through it.
Can I use the WO-YE-M48-42 adapter to attach M42 accessories to my 2" focuser drawtube?
Not directly. This adapter has a male M42 thread on the output and is designed to be threaded into an M42 female port on a camera or other accessory. To attach M42 accessories to a 2" drawtube, you would typically need a 2" nosepiece that terminates in an M42 male thread.
What are the thread pitches for the M48 and M42 sides of this adapter?
While not listed in the specifications, M48 and M42 threads used in astronomy equipment almost universally use a 0.75mm pitch. This adapter is designed for full compatibility with standard M48x0.75 (2" filter) threads and M42x0.75 (T-thread) standards.
