• The correct position for the pointer, scribe is whereever it was when the last pointing model was made.
  
• Looks like the scribe mark is about 1.5 mm wide
• The radius of the encoder is about 60 Ft.
• a 1 mm position error at the pointer is:

• Error location	Error Asecs
  az encoder error	11.3 (little circle)
  on the sky za=5	.98
  on the sky za=10	2.0
  on the sky za=15	2.9
  on the sky za=19.6	3.8

• We probably need to see how repeatable the encoder is by moving back to 270 at a different day.
  

26jan12 - Encoder 1 replaced

•   26jan12 encoder 1 replaced. Equipment, bearings holding encoder were repaired:
• the encoder was full of grease. The maintenance crew should not be greasing the encoder mount since the grease gets into the encoder.
  
• the bearings in the mount holding the encoder were damaged, some were missing. It was rebuilt.
  

• Old encoder prior to replacement (.jpg)
• 1.2 mm right of center of mark
  
• new encoder in position (.jpg)
  
• .3 mm left of center mark
• Picture of dirty old encoder (.jpg)
• the inside of the encoder was full of grease. Claim is that maintenance squirted oil into the encoder, gear when it was making noise. This should not be done.
  
• Ch1 encoder when az at 270 (.jpg)
• Just a reference. this position will depend on which direction they drove to get to za=270 (az bending depends on direction of motion).