The old Double Arm Drive invention is still alive and kicking after all these years. When I recently updated the links on my page, I found that a lot of people still build them despite the extremely short exposure times and stacked processing available with modern digital astrophotography. As a matter of fact, my interest was rekindled a couple of years ago when I bought a Canon T1i and I got out the original Type 3 Double Arm Mount I made back in the 1980′s just for fun. I was able to produce some very nice shots with minimal post processing and no stacking at all.
Here is an example:
This was taken with a modified Canon T1i using a 50mm lens at f 2.5 for 2 minutes 30 seconds mounted on a Double Arm Drive. You can see the Lagoon and Triffid nebulae as smallish red glows near the middle as well as the large dark nebula sometimes called “The Pipe” toward right center.