Trying to Remember How I Did Astrophotography

There are at least different combinations of eyepiece mount extension tubes that I have for Big Bertha.  Trying to remember which to use in darkness was a struggle, so I did some photography with the world's most ungainly lens: 2000mm f/4.5.

This was taken at prime focus of a mountain some miles away.  Naked eye this is a patch of green and brown:

All pictures suffered from too long an exposure.  For some reason, I forgot that I have control over the exposure length.  The picture above was hopelessly washed out; post-processing did not get back the detail lost by too long an exposure.  This picture was done with a 25mm eyepiece in the path (what is called eyepiece projection), and much more magnification:

Same exposure problem.  But I was able to determine that prime focus and eyepiece projection require no extension tube in the focuser.  One extension is all the eyepieces below 500mm focal length.  Two extensions let me use the 85mm eyepiece, made by Russell Machining.