Of a couple dozen shots, only a few taken when the subject was the closest showed any real detail. The image shown above was my best shot. It is shown here as a 100% crop, but it is actually about 1.58 times actual size due to opening it in photoshop at a resolution higher than the native resolution of the camera. (You must click on the photo to see it actual size).
I tried a second attempt Sunday morning at 4:57am, but this time with stacked teleconverters hoping to get an image twice as large with my 1400mm rig. Since autofocus is not an option when using 2 teleconverers, I used manual focus and pre-focused on the moon in order to accurately set the focus at infinity. When the ISS came into view, I found it in the camera viewfiner and took some shots. But as it got closer and near the sweet spot where I could get a closer photo, I lost it and was unable to find it again looking through the camera even though it was clearly visible to the naked eye. The added focal length meant that I was looking at a much narrower slice of the sky when looking through the lens than on my first attempt. This proved very frustrating, but at the same time it was a learning experience. Hopefully I can do better next time.
[click on the moon image below for a larger view]