On the night of Sep 15/16, 2022, physics major Abi von Plinsky and I observed the RR Lyrae star XX And for her capstone project.
The star XX And is a variable star of the RR Lyr "AB" type. Its period may be changing slightly on long timescales -- that will be one focus of our study of it.
The object is located at
RA = 01:17:27.41 Dec = +38:57:02.0 (J2000)
A chart of the field is shown below. The size of the chart is about 31 x 26 arcminutes.
I've marked the location of several comparison stars as well. You can find reference magnitudes for these stars at the AAVSO:
I'm not sure yet which reference star(s) might be best to shift the instrumental magnitudes to the standard scale. These might be good choices:
| Label | B | V |
| C = 111 | 11.575 | 11.101 |
| E = 117 | 12.503 | 11.745 |
I need to take a photo of the finder TV screen.
The sky value shows a falling value as the field rose, with some clouds early on.
The FWHM graph below shows a big drop when we re-focused around image 44.
Using aperture photometry with a radius of 6 or 8 pixels in V (changed with focus), or 10 pixels in B, (binned 2x2, each pixel is 1.24 arcsec, so a radii of 7.4, 9.9, 12.4 arcsec), I measured the instrumental magnitudes of a number of reference stars and the target. Following the procedures outlined by Kent Honeycutt's article on inhomogeneous ensemble photometry, I used all stars available in each image to define a reference frame, and measured each star against this frame.
Sigma-vs-mag plots show that the floor was about 0.011 mag in V, and 0.016 in B. These relatively large values are due to some clouds and the large airmass at the start of the run.
The change in zeropoint shows an increase of up to about 1.5 mag during the cloudy period.
Photometry shows the star fading in a steady manner over the 3 hours of the run.
