On the night of Mar 17/18, 2022, under good conditions, RIT undergrads Nolan Ames, Sebastian Rebelledo, and I acquired images of the delta Scuti star AI CVn = 4 CVn as part of their class project for Observational Astronomy.
This night was a bit hectic and out of order, as the usual computer we use to control the camera would not boot. In desperation, I used my own laptop, and it did work; but our procedures were somewhat haphazard.
Also, it turns out, the amplitude of variations in this object are so small, and the star is so bright, that it is difficult to detect its variations.
The main setup was:
Notes from the night:
The object is located at
RA = 12 23 47.01 Dec = +42 32 33.8 (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.
I'll use star "A" to shift my instrumental magnitudes to the B-band scale.
The sky value shows no clouds during our observations. (the one dip occured when I moved the panel in the dome slit).
The FWHM graph below shows huge values, as we defocused to avoid saturation of the very bright target.
Using aperture photometry with a radius of 15 pixels in B and V filters (binned 2x2, each pixel is 1.24 arcsec, so a radius of 18.6 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 something like 0.010 mag in B, but with so few comparison stars, it's hard to say
The change in zeropoint shows little change.
Last modified 3/26/2022 by MWR.