A nice looking instrument Tony.
I like the idea of a high(ish) resolution version. Like the LHIRES, the chromatic aberrations should be less of an issue. The foot of the lamp lines look rather broad though. Do you think this is down to the quality of the optics? (I think I remember seeing something similar with a batch LHIRES which had poor quality doublet lenses, seen as an “elephant’s foot” shaped lines) . What focal ratio are you running ?
Did you see the results Terry Bohlsen recently posted from his version at similar resolution (presumably also with an 1800 l/mm grating) on ARAS ?
http://www.spectro-aras.com/forum/viewtopic.php?f=5&t=2172#p11890
Cheers
Robin