UT Apr 08, 2024: Photometry of FL Cnc and Inari

Michael Richmond
Apr 11, 2024

On the night of Apr 07/08, 2024, under good conditions, RIT students Rachel Patanella, Veran Stanek, Mimi Harrison, Drew Demers, and I acquired images of two targets: the variable star FL Cnc, and asteroid (1532) Inari.

FL Cnc

This delta Scuti variable star has a short period of about 55 minutes, according to its entry in the GCVS. The amplitude is rather small, and when I investigated briefly some TESS observations of the star, I found that it can vary significantly from cycle to cycle.

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• B-filter 20-sec, V-filter 10-sec images
• images binned 4x4
• no guiding
• focus position on 12-inch:
  • in V: 0.429 yields FWHM 4 at T = 50-ish F?
  • in clear: 0.387 yields FWHM 4.1 at T = 44/6

Notes from the night:

• Clear skies for the entire run.
• no Moon visible
• camera at T = -16 C, after we found that it couldn't hold the usual temperature of -20 C due to the warm air. Took a second set of 10-second darks, "dark10a", which should be used for this evening's reductions.
• air temperature in the dome dropped from T = 65/18 at start of run to T = 44/6 at the end

The picture below shows an image of the field of FL Cnc from this evening. The field of view is about 26 arcminutes high.

I've marked the location of several comparison stars.

  star       name                  B          V         
------------------------------------------------------
    A       APASS9 5628457      10.800     9.358    
    B       APASS9 5628458      10.704    10.111    
--------------------------------------------------------------------------

 

Here's the sky background over the course of the run. No clouds.

The FWHM rose to 5, then was steady.

The graph below shows changes in the photometric zeropoint of an ensemble solution of the instrumental magnitudes over the course of the run. The jump at the start is due to our change in exposure time.

Inari

We switched to the asteroid (1532) Inari at 10:52 PM and continued observing it until 12:46 AM, acquiring 56 images through the clear filter with an exposure time of 60 seconds each.

The picture below shows an image of the field of Inari from this evening. The field of view is about 22 arcminutes high.

I've marked the location of several comparison stars.

  star       name                  B          V         
------------------------------------------------------
    A       APASS9 5226541      11.338    10.827    
    B       APASS9 5226116      12.975    12.273    
--------------------------------------------------------------------------

 

Here's the sky background over the course of the run. No clouds.

The FWHM didn't change much.

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