In the group we always tuned the other instruments to the keyboard. In the old days before all these electronic tuning gizmos we could tune a guitar by ear from one string. Once that is in tune you can tune the others from it. You have 3 open D strings on the tuning you're using. F# will be the 4th fret up on any of them.
Good old Doug....!
You remembered...!
Fantastic....Bleedin' electromic gismos...LOL...!
Standard tuning:
Top E string, (1st) in tune....
Press 2nd string 5th fret. Pluck. Tune to same pitch as top 1st string.
Press 3rd string 4th fret. Pluck.Tune to same pitch as 2nd string.
Press 4th string 4th fret. Pluck. Tune to same pitch as 3rd string.
Press 5th string 4th fret. Pluck. Tune to same pitch as 4th string.
Press 6th string 4th fret. Pluck. Tune to same pitch as 5th string.
Bottom E and top E should now sound exactly two octaves apart in pitch.
Sorted....

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Cheers Doug...!
Paul.
P.S. If you get it wrong....Time to pop to the music shop to get some more strings...

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LOL...

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