This is a 42 mm extension tube that adds 20 mm of length. The outside diameter is 1.8". The male thread is just under 3 mm long and the female thread is about 18.5 mm deep.
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The extension tube is very light but strong. It's much lighter than any other extension tube brands I've ever purchased.
I was in need of help to arrive at 55 mm of back focus so I called Stellarvue and talked with Vic (owner) he spent considerable time with me on the phone calculating exactly I would need given my different cameras and filter wheel combination. Great support - the extenders, variable
Excellent finishing and the threads were perfect.
Excellent finishing and threads were perfect,