Legendary Photograph

Look at this photograph

Here's a one line script you can paste in chat to check which ones are currently active based on which world quests are up right now:
/run print("Currently Available:")local n={"Abu'Gar","Nat Pagle","Oculeth","Time-Warped Fisher","Chen Stormstout","Elder Clearwater","Wrathion"}for i,v in pairs({0,4,25,35,557,584,624})do if C_TaskQuest.IsActive(70075+v)then print("-",n)end end

It will only print out which photographs you can get during the current world quest rotation.

World quests reset biweekly (NA: Tuesday morning and Friday morning; EU: Wednesday morning and Saturday evening.)
If you are unlucky there may not be any Cataloging world quests active at all.

• 
  
• Each world quest will always spawn its specific legendary person in the same spot every time.
• 
  
• Make sure you don't complete the world quest until you have your photograph snapped. Then you can retry if you miss it!
• 
  
• You do not need to finish the world quest to get credit for the achievement.
• 
  
• You can make it easier for yourself by creating a targeting macro and spamming it during the ride
  Spoiler

  
  Here's a macro for Oculeth that you can spam during the ride that will make a sound and a raid warning when you are near him:
  /cleartarget
/tar Chief Telemancer Oculeth
/stopmacro [noexists]
/run PlaySound(8959)RaidNotice_AddMessage(RaidBossEmoteFrame,UnitName("target").." nearby, get your camera ready!",ChatTypeInfo["RAID_WARNING"])
  Change the name after /tar in the second line of the macro to whichever NPC you are currently looking for. Exact names are listed in bold below.
• 
  

---

Where to go for each photo:

• 
  
• Chen Stormstout – Waking Shores (east of Obsidian Bulwark)
• 
  
• Abu'Gar – Waking Shores (Life Vault Ruins)
• 
  
• Wrathion – Thaldrazsus (balloon ride, Algeth'era)
• 
  
• Time-Warped Mysterious Fisher – Thaldrazsus (raft, south of Valdrakken)
• 
  
• Nat Pagle – Ohn'ahran Plains (The Mallakh)
• 
  
• Elder Clearwater – Ohn'ahran Plains (Forkriver Crossing)
• 
  
• Chief Telemancer Oculeth – The Azure Span
• 
  

I'm not sure if it makes a difference, but I tried at least 30 trips down the route in /way 52.09 57.02 Thunderspine Thicket [npc=195227]. He never showed up. I got to looking at the abilities and noticed I didn't have the [spell=367794]. I thought, Nat is suppose to be a legendary, this helps you find legendary wildlife... I went to Dragonscale Basecamp and bought the [spell=367794]. Came back here and first run after buying it, Nat was on the bridge. Did it make a difference? I don't know. Would it be smart to put it in your inventory, I'd say yes. Just in case.