EDHF is the first of the Pentax 75 line. It was succeeded by the EDHF II and later SDHF telescopes that had a marginal improvement in terms of CA. The telescope tube is made from aluminum and has a powdercoat finish. The interior is flat-black and the tube incorporates five baffles that help shield away any stray light. It includes ED glass and has a third element acting as a field flattener sitting right in front of the focuser knobs. The built in flattener has a clear aperture of 45mm and only compresses the focal ratio very slightly (.98x). All three elements has a Pentax Super-Multi Coating.  The focuser lack any fine tuning capabilities and is very coarse and the tube does need certain adapters in order to use accessories other than the original parts. The easiest way is to source a M50 to M48 adapter.