Bert,
The stars in your Eta image (taken at 300mm) are square. They look square on my PC, Toshiba laptop and MacBook Pro. They look square if I download the image from Sydney or San Francisco (my current locale, the Napa Zinfandel is not too bad
)
There is a reason for this....which I can only glean you don't get either...
or should we move onto Nyquist sampling and Bayer matrices?
By the way, at 14mm a wooden pole tracks quite well, particularly when using 15 micron pixels.
How about you shoot the same object using an EQ6 at 3000 mm (or so), a few hours would be nice. Then we can start comparing apples with apples.
Take is easy
Peter