Field Astigmatism vs. Alt,Az¶
Here are plots of the "field" astigmatism Y and X vs. Azimuth, for different values of Alt, from the 10/02 scan. By field astigmatism I refer to an aberration constant across the focal plane. This pattern of aberration is not caused by collimation error only figure error. As you see there is a clear sinusoidal pattern indicating that there is field astigmatism that could be corrected by adjusting the primary mirror figure.
Field Trefoil vs. Alt,Az¶
Here will be plots of the "field" trefoil X and Y vs. Azimuth, for different values of Alt, from the 11/20 scan.
Residual Coma and Astigmatism 11/11 to 11/17¶
For images taken between 11/11 and 11/17, here are plots of the Coma and Astigmatism from the donut analysis. These plots are of the overall difference between the donuts from an image and the reference wavefront. The reference wavefronts are from a few images taken at Zenith, and with Steve's collimation, during commissioning. Only the ComaY shows a systematic difference from the reference, although there are a few images with larger values of AstigX. However, none of these values are all that large, indicating that the wavefront does generally look reasonable on average.
For all images taken from 11/11 to 11/17, here are comparisons of the AstigmatismY(ThetaX) vs. AstigmatismX(ThetaY) and AstigmatismY(ThetaY) vs. AstigmatismX(ThetaX). The former should show that AstigmatismY(ThetaX) ~ AstigmatismX(ThetaY) and the latter that AstigmatismY(ThetaY) ~ - AstigmatismX(ThetaX). This is indeed the case.
These plots also show that generally the angle of the Astigmatism aberration surface is rather small. These slopes are in units of [Waves]/[mm], and with the focal plane 180mm in radius, the deltaAstigmatism at the edge of the field for an angle of 0.001 is just 0.18 waves.