Salmon Ruins, Bloomfield NM

Room 82

Summer Solstice

 Sunlight streams in through a special ceiling high window for several months every summer.  The full light moves across the original Chacoan floor for about only four weeks from mid-June to mid-July and marks the summer solstice by fully covering the north rock on the altar.     Partial sunlight moves through the room for a few additional weeks. From September to April the sunlight is only a small sliver on the north wall or entirely gone making the room an ideal location to watch other sky events during the winter months.

 First, a short background story:

   In April, 2008, I was taking a variety of time lapse photos at various time of the day, I had completed a sequence of photos at the sample pit house for equinox and set up some cameras in a few other places.  Around the beginning of May, I noticed where the shadow/sunlight was in room 82. This room was recognized as a possible 'astronomy' room because of some unusual features, such as the window in the east wall.  This ceiling high window has a sloped sill which remains to this day. Another feature was described as an 'altar' in the descriptions and notes. First I took some measurements of the room and how the altar might fit.

 
From book and field notes, the “altar” is at the west wall, approximately 10cm high (L.B. recollection) and less than 20 cm below door sill level (P.R. commented on 30cm door sills). Pictures indicate over half way across back wall.

From window sill to back (NW) corner is 5.5 meters

The test Board dropped into the back wall is 60cm long and has a 10cm circle

On May 29, 2008

A simulated altar about 30 cm X 110 cm  was left in the bottom of the floor of Room 82 with features 71 and 72 approximated. The placement is  about 30 cm from the west wall and about 10 cm from the north wall to compensate for the relative height change from original ‘altar’ top position to where the floor would be without the present fill.        Bruce and Mike were very helpful to the altar and pebble placement.

 Sun positions are from Starry Night Backyard software 2000 edition, WWW.Space.com, the bearing is either (t) true or XXXm magnetic.

June21, 2008 sunrise is at 5:54 am

7:30 am @ -17 incline, bearing is 73t degree,   (-11+180=242m)

*7:45 am @ -20 incline, bearing is 75t degree (244m)

7:55am @ -22 incline, bearing is 76.5t degree (245.5m)

*8:12 am @ -25 incline, bearing is 78.5t degree (-11+180=247.5m)

8:22 am @ -27 incline, bearing is 80t degree (249m)

8:36 am @ -30 incline, bearing is 82 degree (251m)

*8:52 am @ -33 incline, bearing is 84 degree(253m)

* white pebble positions

  Interesting features about room 82

1. Window with sloped sill

 2. ‘Altar’ feature noted as unusual.

 3. Rock (feature 72) clearly marks summer solstice.        Probable intent.

 4. Future research on next rock (feature 71) .

 sun covers the right rock on the altar from 7:45 to 8:00 am

Making the altar    -    parts

a little fine tuning

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Other observations

   The ‘not to scale’ field sketch indicates an L20-49 item (Possible description could be located) and a L3.5-20, F73.     From Salmon Book, edition 1, (Fig 8.76) the Feature 72 is in an ideal position for identifying the summer solstice. These rocks could have been placed in the identifying position and then the ‘altar’ built up around the rocks to keep them in place. .

     A possible advantage of having a room to observe the sky (stars, planets, or moon) is being out of the weather. Otherwise, a person would have to stand outside and spot a partial moon at seemingly random times, It would be more convenient to be in a warm, dark room and watch the moonlight coming in through a window.  This way, work (grinding, weaving, milling at feature 86) could be attended to, room kept warm by the hearth, jacal wall could keep cold out and minimal moonlight could still be seen crossing the ‘altar’. Decoration on the west wall also could have given the watcher a forewarning.  Another possibility is that the altar could have been a seat (looking out) with certain spots located to see if the moon is visible and to what extent.  

     Future research will determine the height of adjacent rooms for clearance (the right height will limit the start time for the sunlight entering the room as the sun crests the room(s) to the east. Another variable is the height of the Jacal wall, about 1.5 meters will shorten the height of the sun box so that only the altar feature 72 will light up and the sunlight will not track across the floor.

    Salmon Ruins, Bloomfield, New Mexico

  Room 82  The Solstice Marker

Comparison of sunlight positions, beginning and end of May, and Summer Solstice