Just wanted to ask, which 400
then saw sthe poll, so the 400/5,6 (would have been different for 400/3,5)
my 3 cents:
Landscape and Moon photography one would assume that a tripod ist used
For bird photography it is important which kind of birds whether Static or BIF, work from a hide or just "on the fly" is in mind
Key issue is here how good you feel in Manual focusing skills, how good your eyes are and whether you badly need AF.
Df is not the dedicated Fast AF camera though and yes good bird photos have been achieved with MF some days ago
the 400/5,6 was the first IF-ED tele lens I ever had, not forming a too good combo with the TC14 and needs good tripod support (tends to vibrate easily) for your landscape and night plans. Not easy to get accurate focussing quickly. Sometimes LV is recommended (not during action).
It is the most lightweight lens though, so carrying and sustained handhold use is on the plus side here - no alternative to get that range for that weight and size
plus:1400$ for this lens plus TC14B sounds way too expensive!
500/4 probably will give you best IQ (never used this particular lens but the AF-S first version which still is one of my finest lenses) but is the most bulky and heavy one, good for tripod work
200-500 for the fastest workstyle, best handhold capability with AF and sometimes VR, best versatilty but not so good for tripod I'd say
