UT Apr 16, 2024: Photometry of transit by HAT-P-36

Michael Richmond
Apr 17, 2024

On the night of Apr 15/16, 2024, under poor conditions, RIT students Joey Root, Vincent Fittos, Joe Bianchi and I acquired images of the exoplanet system HAT-P-36. They are part of the PHYS 373 "Observational Astronomy" class, and their project is to measure the change in this star's brightness as the planet passes in front of it.

Unfortunately, clouds came and went throughout the night, blocking our views of the exoplanet's ingress and egress. Rats.

HAT-P-36

The entry for this star in NASA's Exoplanet Archive has a wealth of information about the system. The transit has a depth of about 0.018 mag and a duration of about 2.2 hours.

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• clear filter, exposure time 60 seconds
• images binned 4x4
• no guiding
• focus position on 12-inch:
  • in clear: 0.549 yields FWHM 6 at T = 58/14

Notes from the night:

• clouds at sunset, disappeared for a while, then returned intermittently throughout the night. They ruined measurements for several blocks of time throughout the run.
• almost first-quarter Moon high in southwest
• camera at T = -18 C
• camera lost a proper connection with the camera after image 32, entering a state in which it "takes" an image every few seconds, without any readout time or exposure time. Before we noticed and stopped the camera, it "took" almost 400 bogus images. To restore normal behavior, I had to quit MaximDL, unplug the power and USB connection to camera, re-insert power and USB, and re-start MaximDL.
• temperature dropped from 58/14 at start of night to 47/8 when we quit at 1:18 AM

The picture below shows an image of the field of HAT-P-36 from this evening. The field of view is about 22 arcminutes across.

I've marked the location of several comparison stars from APASS9.

  star       RA       Dec          B          V         
------------------------------------------------------
    A    188.28014  +44.9378       11.791   11.548  
    B    188.20519  +44.7781       12.173   10.499  
    C    188.44432  +44.8609       11.619   10.717  
------------------------------------------------------

 

Here's the sky background over the course of the run.

The FWHM:

The graph below shows changes in the photometric zeropoint of an ensemble solution of the instrumental magnitudes over the course of the run.