The Digital Camera below is how it would normally appear when switched off, but take note of the dark ring on the outer edge of the two component zoom lens. This is what I refer to as the lens hood. On most cameras this has got an internal thread; usually metric and is normally at 0·75mm pitch. (The pitch is the distance between the point of one thread and the next.) This is the thread used on most T Mount adapters so you can easily compare it.

This view shows the camera switched on and the zoom lens at maximum extension. As you will appreciate this extension has to be considered when planning an adapter. Normally the lens needs to be as near to the focal plane of the telescope as possible and if the adapter is of the type which fits into a 1·25" draw tube, as many are, the lens will need to sit about 1mm away from the shoulder at the draw tube inner end of the adapter. The next thing is, you will need to measure the thread size in the lens hood, if this is 0·75mm pitch then you can expect it to measure around 41·0265mm, if for example the thread diameter is 42mm. So the internal finish size for a thread at 0·75mm pitch is the size of the major diameter of the thread minus 0·9735mm. Your handbook may give the thread size or if you already have a sleeve adapter for mounting filters or an external lens hood it would be easier to obtain the information from these sources. The depth of thread in the hood will be needed. If the pitch is known then counting the number of threads is sufficient. The next thing to measure is the size of the largest diameter part of the zoom lens.

Once you have done this you are well on the way to designing your adapter.