UT Mar 29, 2024: Photometry of SZ Lyn

Michael Richmond
Mar 29, 2024

On the night of Mar 28/29, 2024, under fair conditions, RIT students Owen Cheevers, Owen Racette, Rae Mailly, and I acquired images of the delta Scuti variable star SZ Lyn. They are part of the PHYS 373 "Observational Astronomy" class, and their project is to make a light curve of the star.

We acquired images in B and V passbands, getting a bit more than one full period through both filters. Clouds ruined the final hour of our observing run.

SZ Lyn

This pulsing variable star has a very short period of about three hours, with an amplitude of roughly 0.3 mag in V-band. It's a pretty easy target at ninth magnitude.

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• B-filter 30-sec, V-filter 10-sec images
• images binned 4x4
• no guiding
• focus position on 12-inch:
  • in V: 0.280 yields FWHM 4.2 at T = 41/5

Notes from the night:

• light clouds came and went for four hours after sunset. Around midnight, heavy broken clouds appeared and stayed until we quit at 1:08 AM.
• waning gibbous Moon rose in the middle of the run
• camera at T = -20 C
• air temperature in the dome dropped from T = 41/5 at start of run to T = 32/0 at the end
• first eight V-band flatfields were full of garbage, due to a camera connection issue. Disconnected and reconnected, after which problem did not recur
• the dome partially occulted the telescope for a short while in the middle of the run

The picture below shows an image of the field of SZ Lyn from this evening. The field of view is about 22 arcminutes across.

I've marked the location of several comparison stars.

  star       name                  B          V         
------------------------------------------------------
    A     APASS 6365302        12.154     11.327 
    B     APASS 6365252        11.850     11.391 
--------------------------------------------------------------------------

 

Here's the sky background over the course of the run. The appearance of clouds is obvious.

The FWHM improved slightly as the temperature dropped.

The graph below shows changes in the photometric zeropoint of an ensemble solution of the imstrumental magnitudes over the course of the run. The first increase is probably due to improper positioning of the dome; the second is due to clouds.