Sorry for being off-grid recently – a very unpleasant cold after returning to the UK!
Yes, the vernier adjusts the grating as standard. I’d just placed everything so as to zero in on Ha. I can effectively ‘lock-off’ the adjustments to stay Ha orientated. That’s what I crudely mean by Ha ‘tuned’.
I’ve just refitted both the ‘printed’ scpectroscopes ready for observing – just need a break in this terrible weather! Oh, for Arizona skies!
PS, I got Wayne’s latest treatise and will respond asap.