These are 5 position alpha-numeric codes comprising the d series. All other level II codes and descriptors are approved and maintained jointly by the alpha-numeric editorial panel (consisting of CMS, the Health Insurance Association of America, and the Blue Cross and Blue Shield Association).
Alaska: Although Alaska enjoys a high volume of aurora activity, its cruises are not often mentioned as northern lights cruises. During the Alaska cruise season, it's rarely dark enough for the lights to be visible.
Your best chance to see the northern lights is during the cold, clear winter nights between September and April. The prime time to see them in all their glory in usually after midnight. Be spontaneous, brave the cold, and embrace a late night adventure to see the stunning natural phenomena Alaska is known for.