2.19
Working on paper figures. Concern that the plots we made for the 1000 image sequence are dominated by drift from the source separation in a given pair of beams. Some example plots of this are below.
The red line is temperature and the blue is source separation, for different pairs of beams. We want to compute a running mean for this data and subtract it for all source separation values before taking our standard deviation.
- compute running mean
- subtract out
- separate sequence of 1000 images into 100 image sequences and see if the dome seeing decreases
The computed running mean with a window of 20 points is shown in the figure above. We now take this mean and subtract from the y source separation values for beam pair 0.
The new plot looks relatively similar to the previous 1000 image plot (shown below); the x pairs are much flatter
Old plot:
Elana also had the idea to compare this with the ellipticity of our first batch of on-sky data points, so we can make a stronger argument that this dome seeing is directional.
Procedure
Galsim, make a box around each star to find the PSF
Rotate the ellipticity back around into the correct x,y frame
Coordinate transformation is the same as before to figure out the major/minor axes
2.20
- Ellipticity components
- Make new figure with running mean lines displayed for x/y source separation over 1000 images
Elana sent me a source that breaks down ellipticity and what it means.
I have a code block that calculates the ellipticity components e1 and e2 given the approximate coordinates of a star. I calculate ellipticity and its components e1 and e2 (stretching along x/y and y=x/y=-x). Once I calculate the components, the ellipse's major axis is at an angle a = 1/2 arctan(e2/e1) from the positive x-axis, so then I can calculate what the rotation of the focal plane was for this image, and from that back out this angle in that reference frame.