The window of the furnace room was located on the east elevation of the house. The sun, of course, rose in the east, but at 7:20 am, according the National Weather data for Dec. 26th. The moon was setting in the west on the opposite side of the house. Consequently, there was no ambient lighting entering the furnace room window. Fleet looked into thw wine cellar at about 6:15 am.

There was artificial light in the hallway and furnace rooms, one, or perhaps two bulbs; the typical ceiling height for a house is 8' but basement ceilings sometimes are lower. If the wine cellar door is 6'-8" high, as is typical for doors, then judging from the photographs, the basement ceiling is at 7'-6". Fleet was about 6'-4" tall (?) and a pretty big fellow, at least according to John Ramsey. The child's body was on the floor in the wine cellar, mostly hidden by the L turn in the wine cellar. That means that most of the light that might have been blocked from illuminating the wine cellar floor at least. I think a case could also be made for his eyes not adjusting to seeing into a dark room, called dark adaptation, similar to walking into a darkened theatre where for a moment or two you don't see anything unless the screen is lit up and illuminating the chairs and patrons.

Conversely, at 1:00 pm. there was ambient light entering the room. John is much shorter, I think about 5'-9". When he opened the door there would have been some light in the room reflected into the wine cellar. I honestly feel this explains that much of what happened in the basement.

http://b.heart.50megs.com/ramsey/Light_and_the_WR.htm