Another project while I wait (and hope) for the clouds to clear. I have been trying some camera lens photography with my Meade DSI. Using a Mogg adapter I am able to achieve focus with my DSI I and II OSC, but not with the DSI III Pro, due to the housing for the filter slide.

I did consider sacrificing my original DSI IC OSC to produce a low profile adapter with T thread, but ended up modifying a PK-C adapter. Although this would not reach focus when connected using a C-T2 mounting ring, I looked for ways to reduce the length. Fortunately the C mount step ring is attached with three tiny 1mm grub screws; once removed the reducer can be knocked out of the adapter, leaving a step ring of suitable size to attach to the T2 mount on the DSI (rev a and b).

Without the means to cut a T2 thread, I decided to file and sand this down, to just fit comfortably within the threaded T2 mount. Reversing the grub screws, I have been able to reverse fit these and ‘lock’ the adaptor inside the T2 mount, without damaging the threads. Pretty fiddly, using a 1mm hex wrench, and a piece of cardboard to protect the DSI chip!

Finally I drilled a hole into the bottom of the adaptor to secure this to a mounting block from my ADM rail (or a standard tripod). As the adapter is made from aluminium, I was able to ‘thread’ this, using the steel screw from the mounting block (rev c).

Success, my 28mm, 50mm and 70-210mm Pentax zoom lenses now reach focus, and I am able to insert relevant filters into the DSI III Pro slide. I’m looking forward to taking some tracked ‘wide’ field images with my new setup, which sits happily on top of my 8” SCT.

The attached is a quick and dirty 2.5’ exposure of the star fields around Perseus taken with my 50mm lens at f4 through a hole in the clouds (rev d). Manually focusing these lenses is likely to be tricky...perhaps the next project will be to build an electric focuser...