Extension tube for astrophotography, M54/M54 16 to 20 mm | Askar

Your flattener or reducer only works properly if the camera sensor is at the correct distance. If the backfocus isn’t correct, you’ll see that in the corners of your footage. Therefore, when using an extension bus, pay attention to the length and the threaded connection, such as M54 or M48.

This extension bus from Askar has M54 threaded connections and a length range of 16 to 20 mm. It belongs in the image chain between a flattener for astrophotography or a reducer and your camera. If a part comes with T2 or M48 afterwards, then you might have an adapter between T2 and M48 needed.

Calculate the entire image chain in advance: the backfocus that requires flattening or reduction, minus the length of the camera, filter holder, and other intermediate parts. This way you can see if this bus fills the gap that remains. Also check on each side which wire is inside and whether it is the inner or outer wire.

If you want to be able to rotate your camera without having to unscrew anything, check out the camera rotator with M54 connection.