I can agree with the Zeta Herculis at last sentiment at the start of this thread. Encouraged by the posts here on Cloudy Nights and advice from John Huntly I have at last seen Zeta Herculis on two separate nights from here in the UK. On both nights the telescope used was a TMB 130mm f9.2 Apo-refractor.
First time was on the 21st July 2020 with a Tak prism diagonal and a 4mm Circle V Ortho for about x300. Secondary appeared as a very condensed yellowish oval sitting on the first diffraction ring at about the right position angle relative to a white primary.
Second time the 14th August 2020 with the same Tak prism using a 9mm Morpheus (x133) a 8mm Brandon (X150) a 5mm Tak LE (x240) and the same 8mm Brandon with a x1.5 Magic Darkin for 5.3mm (x225). All eyepieces had been recently cleaned or the case of the Morpheus it was virtually brand new.
With the 9mm Morpheus I was surprised to very occasionally a tiny white fleck at about the right position, a convincing observation. With the 8mm Brandon the same flick appeared as a definite tiny point like a white LED flashing on and off.
With the 5mm Tak LE the same position of the previously seen fleck became a definite faint yellowish condensed part of the first diffraction ring very similar to the view with the 4mm Ortho back in July.
With the barlowed 8mm Brandon the secondary managed to be definite small disk on the first diffraction ring, very similar to a sketch that John Huntly was kind enough to send me.
There have been of course been many failures