Apr 09, 2026 UT: video of Jupiter, photometry of NN Boo

Michael Richmond
Apr 09, 2026

On the night of Apr 08/09, 2026, under very good conditions, PHYS 373 students, Anika Kumar, Dr. Melso, and I collected data on two objects:

• video clips of Jupiter in filters B, V, R, I, with 1000 frames per clip
• photometry in B,V of the RR Lyrae star NN Boo

Tonight was clear until the end of the run at 3:30 AM, and dark: very good conditions. One minor equipment malfunction: the main camera and MaximDL had a communication failure in the middle of the night, leading to a loss of NN Boo data for about 17 minutes. will be an on-going project for this group.

NN Boo

NN Boo is a pulsing RR Lyrae star with a relatively short period of about 8.5 hours. If we can measure its average magnitude over the course of a cycle, we should be able to estimate its distance via the inverse-square law. How well will that estimate agree with the distance determined via parallax by Gaia?

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• B and V filters, 60 sec exptime
• images binned 4x4
• guiding with 10-sec exposures at first (at large airmass), then 5-sec exposure later. Put target at (740, 1160) to get a decent guidestar.
• focus position on 12-inch:
  • V = 0.221 yields FWHM ?? pixels at T = 51/10
  • V = 0.249 yields FWHM 5.4 pixels at T = 40/4

Notes from the night:

• sky was clear until very end of run, when a few minor clouds appeared
• no Moon until around 3 AM, when it was low in SE, behind trees
• camera at T = -15 C
• temperatures were not too chilly: T = 51/10 around sunset, dropping to 40/4 at 3:30 AM
• students from Group I in PHYS 373, "Observational Astronomy," came to observe NN Boo

The picture below shows an image of the field of NN Boo taken last night. The field of view is about 20 arcminutes wide.

Here's the sky background over the course of the run. The short horizontal stretch is the time when the camera and computer lost communications; those data are simply copies of the first image during the stretch.

The FWHM was pretty steady.

The graph below shows changes in the photometric zeropoint of an ensemble solution of the instrumental magnitudes over the course of the run. Note the decrease as the field rises, then the increase as it passes the zenith and begins to set. The outliers are due to trailed images.

Using aperture photometry with a radius of 7 pixels in V filter (binned 4x4, each pixel is 1.036 arcsec, so a radius of 7.3 arcsec), and 7 pixels in B filter (binned 4x4, each pixel is 1.036 arcsec, so a radius of 7.3 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 in V-band was about 0.007 mag in V.