Measured horn positions

1. The beam under the floor by the sbn receiver was removed to work on the seti IF box. This caused the floor to shift. The beam was replaced and then this receiver was remeasured. After the measurement, the turret position was moved to 76.83 deg.
2. After the measurement the horn was moved up .44 inches. The turret was moved 161.99 -> 162.34. This turned out to be the wrong turret direction to move. The next survey measured twice the error.
3. The large y error was because the turret was moved the wrong direction on 04feb02. After the measurement the turret was moved to 161.50.
4. After the measurement, the lbn turret position was moved to 310.14.
5. After the measurement the lbw turret position was changed to 286.52. This looks like it was the WRONG direction.
6. After the measurement, the sbtx turret position was moved to 62.16 deg. This was the WRONG direction
7. After the measurement the sbw turret position was moved to 103.8->103.88 degrees.
8. After the measurement (and getting the sign right!), the turret was moved, 124.99->125.827 degrees.
9. 21aug02 lbn horn moved down 3.84 inches to correct for phase center error.
10. 28aug02 cband horn moved down 1.08 inches to put phase center at focus.
11. jan04    receivers moved on floor to get ready for alfa installation.
12. 14feb04. The 11feb04 survey yCorrection was set to zero by moving the turret positions and then the 14feb04 survey was done.
13. 14feb04 sbhigh was moved down .91 inches before the survey to put the phase center at focus.
14. 14feb04 sbw was out of focus in z. It was not moved down because there was no more adjustment room on the mount. We need to make a new bracket.
15. Alfa x listed is measuredCorrection - 1.063 . Alfa wants to be 1.063 downhill from the nominal focus to balance the outer feeds.

Survey notes:

• 28apr04: after kevlar cables and alfa installed. The tilt values were small and were not reported.
• 02may04: Horn survey after horns moved (sbtx,sbrx,lbw,sbw(focus) were not moved). The corrections quoted are after the turret postions were updated. Previous surveys (11feb04 till 01may04) had been using an "old" secondary reference set for the secondary.  On 01may04 we switched back to the "new" set. This caused a motion of about .45 inches y (.37 turret degrees). The turret position for cbh_2, lbw,alfa  were also updated by .37 turret degrees because of the reference system change (even though they were not measured).
• 08may04:The turret encoder lost its position index on 06may04 (alfa cover broke encoder). I aligned the encoder tracking some lbw sources. Mike and Ellen then surveyed sbtx,sbn, and cbh_1. Using all of the measurements there was a -.027Deg  (before-after) difference in the turret encoder. This is .034 inches or -1.199 arcseconds on the sky. Since this is small we'll continue to use the turret positions computed by lynn. If you wanted to correct  for this, you would subtract .027 turret degrees from the offset i've put in the encoder offset of the little stars. The current offset in the little stars is 40843 enc counts. The correct value should be: (40843 - (.027TurDeg*477.867TurDegToEncCnts))=40830 encoder counts.
• 31oct12,02nov12 (see below)
  

31oct,02nov12 horn surveys (top)

    A new sband narrow horn was installed on 28oct12. Lynn surveyed the sbn and sbtx horns on 31oct12. He surveyed the rest of the horns on 02nov12. An "old" (pre may04) secondary reference file  was used for the theodolite shooting. This data set was used for the sbn and sbtx analysis. Lynn did a comparison with the old and "newer" secondary references and saw little difference. All of the other receivers were analyzed using the newer secondary reference derived from the 28jun04 videogrammetry.
    On 02may04 this "old" secondary reference was also used. At that time it was thought that there was a .45" y error between the two system (see 02may04 above).

Some comments on the various receivers:

• sbn
• New receiver. Had to move the floor  location since the new receiver was bumping up against the transmitter.
• turret position used for last measurement was79.6143.
• The errrors,corrections reported here are used the old secondary reference.
• in 02may04 this reference set was also used. later analysis showed a .45 inch y offset between old and new ref sets.
• after the survey was done, i moved the final sbn turret position to 79.967 deg (to correct for this .45 inch error).
  
• After taking into account the tilt errors, this may have not been the optimum solution.
• The sbn receiver was lifted in Z 1.2 inches on 26nov12 to correct for Z the measured z error. It was not resurveyed.
  
• sbtx:
• shot 3 times. 
• final turret was 61.9441
• correction was  .181 inches or .181*.7973(turdeg/inch) = +.1418 deg.
• this would give 62.086 deg for turret
• there would also be a possible .45" correction for the old secondary ref set
• giving 62.44 tur deg pos
• I'm leaving the tx turret position unchanged: 62.29 turret deg.
• sbw,lbw,cb,xb,cbh,alfa,sbh
• All analysis done with latest 28jun04 videogrametry survey data.
• The turret positions remained as they were prior to the 02nov12 survey.
  
• I did not correct the turret position to minimize the y error..

• These are taken from the large table above.
• The numbers are corrections. You need to move the feed by this amount. This is the negative of what lynn reports.
  

Plotting the corrections for each receiver:

• The data is in dome centerline coordinates.
• X positive up the azimuth arm
• Y perpendicular to azimuth.+ is towards the stairwell. This is the turret direction for small turret moves.
• Z focus. + is up.
• colors show the different errors:
• Black:X
• Red : Y
• solid line uses turret position of measurement
• dashed line uses current turret position (11jan13).
  
• Green: Z or focus.
• The data shows the amount to move the feed to correct for the error. (this is the negative of lynn's reported errors).
• Top: The Correction need in inches
• Bottom: The correction needed in lambdas (using the lambda for the center of the feed).

Lynn's emails and reports:

• 06nov12 preliminary survey report (.pdf)
  
• 14nov12 email (.pdf)  sband  horns, plans.
  
• 19nov12 email (.pdf)
• survey results of sband horns (.pdf)
  
• 16dec12 email (.pdf) other receivers
• survey results of other horns (.pdf)
  

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