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Analysis of September Engineering Regression data

The September regressions analyzed were taken on two nights, September 19 and 21. Neither night completed the script, but both took a majority of the exposures scheduled. On the first night, September 19, the AOS mode was AOS-5, whereas September 21 used AOS mode AOS-1.

Image quality

We used the September regression data to study if the different AOS modes cause visible difference in image quality. We study relative changes from the 1st to the 2nd, 3rd and 4th exposure in each block. We define quantities called delta_r50 and delta_whisker as the difference in seeing (r50) between the 2nd and 1st, 3rd and 2nd as well as 4th and 3rd image of each block of 4 exposures taken at the same position.

Seeing Deltas

The left histogram is from the 1st and 2nd images, the next is from the 2nd and 3rd images, and the last histogram is from the 3rd and 4th images in each block.

These three are from the first night, September 19, with AOS-5

As can be seen, there is an improvement in the RMS values from the first difference to the second difference.

Here is the same set of plots for the September 21 data, with AOS-1

The improvement in RMS values is not present in this set.
Seeing was obviously much worse in July. No clear trend can be seen in either set. Note that the 4th exposure in each block had a 90 second exposure time.
Also focus was actively maintained for both tests.

Ellipticity Deltas

The left histogram is from the 1st and 2nd images, the next is from the 2nd and 3rd images, and the last histogram is from the 3rd and 4th images in each block.

These three are from the first night, September 19, with AOS-5

As can be seen, there is an improvement in the RMS values from the first difference to the second difference.

Here is the same set of plots for the September 21 data, with AOS-1

The improvement in RMS values is not present in this set.

From these two studies it seems that the AOS may be making improvements to image quality when it is on.

The same analysis was done for June and July, and is avaliable here, under the Seeing heading.

Ellipticity (whisker): First of set analysis

The whisker values of the corresponding exposures of each set were compared for the two runs. The conditions were similar between the two nights.

The histograms of the whisker values those nights are below.

The differences in the whisker values, calculated as the first of each set's whisker value on the 19th minus the corresponding exposures whisker value on the 21st, are shown in the histograms below.

Offsets

Histograms of the offsets during the two sets are shown below.

Declination offsets

There does not appear to be any clear change in the severity of the declination offsets between the two regressions.

RA offsets

Although the mean of the RA offsets is much closer to 0 for the regression with the AOS in AOS-1 mode,
the RMS also increases.

The more important result is the noticeable improvements in the offsets in the September regressions when
compared agains those of the June regressions. The June regressions were taken in AOS-5 and the July were taken in AOS-1.
The July and both September regressions have similar offsets, but the June offsets are much farther from 0, with a larger spread
as well. The June and July regresssions can be found here