## PointingModelOffsets » History » Version 16

*Lucas Beaufore, 07/12/2013 01:30 PM *

1 | 1 | Lucas Beaufore | h1. Pointing Model Offsets |
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2 | 1 | Lucas Beaufore | |

3 | 1 | Lucas Beaufore | In order to study the effects the pointing model may have on the offsets, new offsets were calculated with possible corrections from the effects of the hexapod trim values. |

4 | 2 | Lucas Beaufore | |

5 | 2 | Lucas Beaufore | The following histograms show the distribution of the offsets before trim corrections, and with a trim correction of both addition and subtraction. |

6 | 2 | Lucas Beaufore | |

7 | 2 | Lucas Beaufore | |

8 | 3 | Lucas Beaufore | RA offset with: No correction, addition of a scaled (.0176 arcsec/micron) trim_dy value, subtraction of the scaled trim_dy value |

9 | 3 | Lucas Beaufore | |

10 | 2 | Lucas Beaufore | |!{width:100%}dec_standard.png! |!{width:100%}dec_corrected_y.png! | |!{width:100%}dec_corrected_minus_y.png! | |

11 | 3 | Lucas Beaufore | |

12 | 3 | Lucas Beaufore | Dec offset with: No correction, addition of a scaled (.0176 arcsec/micron) trim_dx value, subtraction of the scaled trim_dx value |

13 | 3 | Lucas Beaufore | |

14 | 2 | Lucas Beaufore | |!{width:100%}ra_standard.png! |!{width:100%}ra_corrected_x.png! | |!{width:100%}ra_corrected_minus_x.png! | |

15 | 4 | Lucas Beaufore | |

16 | 4 | Lucas Beaufore | The effect of the corrections are arguably more visible on a 3D plot. The following show the tweak values and exposure ID values (essentially time, in order to better show the exposure groups) |

17 | 6 | Lucas Beaufore | versus the offsets. |

18 | 1 | Lucas Beaufore | |

19 | 6 | Lucas Beaufore | Blue = Original offsets |

20 | 6 | Lucas Beaufore | Green = Original offsets + (.0176 * trim) |

21 | 10 | Lucas Beaufore | Red = Original offsets - (.0176 * trim) |

22 | 6 | Lucas Beaufore | |

23 | 1 | Lucas Beaufore | Declination offsets vs trim_dy (vs expid): |

24 | 1 | Lucas Beaufore | |

25 | 9 | Lucas Beaufore | |!{width:100%}dec_all_corrections_back.png! | !{width:100%}dec_all_corrections_side.png! | |

26 | 5 | Lucas Beaufore | |

27 | 6 | Lucas Beaufore | RA offsets vs trim_dx (vs expid): |

28 | 1 | Lucas Beaufore | |!{width:70%}ra_all_corrections_side.png! | |

29 | 10 | Lucas Beaufore | |

30 | 11 | Lucas Beaufore | By applying trim corrections, the offsets should no longer include the part of the offset due to hexapod corrections. |

31 | 10 | Lucas Beaufore | As can be seen, adding the correction (green) makes each set of four data points taken in the same position much more horizontal, removing correlation with trim values. |

32 | 1 | Lucas Beaufore | Subtracting the correction makes each set of four data point correlate much more strongly with trim values. |

33 | 11 | Lucas Beaufore | |

34 | 11 | Lucas Beaufore | After applying the correction, the offsets can then be reexamined for correlations with the telescopes position. The plots below illustrate the relations. Each set of graphs |

35 | 13 | Lucas Beaufore | has the correction applied in each of the directions. |

36 | 11 | Lucas Beaufore | |

37 | 11 | Lucas Beaufore | The following two plots show the Declination offsets plotted against the declination of the telescope. The color scale shows the HA of the telescope. |

38 | 11 | Lucas Beaufore | |

39 | 14 | Lucas Beaufore | No correction, correction added and correction subtracted, respectively |

40 | 14 | Lucas Beaufore | |!{width:100%}dec_teldec_ha.png! |!{width:100%}dec_corrected_teldec_ha.png! |!{width:100%}dec_neg_corrected_teldec_ha.png! | |

41 | 11 | Lucas Beaufore | |

42 | 11 | Lucas Beaufore | |

43 | 11 | Lucas Beaufore | The following two plots show the RA offsets plotted against the declination of the telescope. The color scale shows the HA of the telescope. |

44 | 11 | Lucas Beaufore | |

45 | 14 | Lucas Beaufore | No correction, correction added and correction subtracted, respectively |

46 | 15 | Lucas Beaufore | |!{width:100%}ra_teldec_ha.png! |!{width:100%}ra_corrected_teldec_ha.png! |!{width:100%}ra_neg_corrected_teldec_ha.png! | |

47 | 1 | Lucas Beaufore | |

48 | 13 | Lucas Beaufore | |

49 | 13 | Lucas Beaufore | |

50 | 16 | Lucas Beaufore | h3. Interesting observations |

51 | 12 | Lucas Beaufore | |

52 | 12 | Lucas Beaufore | By adding the correction, the range of offsets decreases, and the correlation of the offsets with trim values is mostly removed. However, the offsets are on average FARTHER from 0 |

53 | 12 | Lucas Beaufore | |

54 | 12 | Lucas Beaufore | By subtracting the correction, the range of offsets increases, and the correlation of the offsets with trim values is mostly remvoed. However, the offsets are on average CLOSER to 0. |