UT Mar 05, 2024: Photometry of (1532) Inari

Michael Richmond
Mar 05, 2024

On the night of Mar 04/05, 2024, under good conditions, RIT students Mimi Harrison, Jason Sergio, Sebastian Montes, and I acquired images of the asteroid (1532) Inari. They are part of the PHYS 373 "Observational Astronomy" class, and their project is to make a light curve of the asteroid.

We experimented with different exposure times, and determined that in order to reach the precision required to submit our measurements to the ASPIREastro.net collaboration, we need to use unfiltered images of at least 60 seconds duration.

(1532) Inari

This asteroid has a rotation period which is thought to be around 25 hours, with an amplitude of about 0.09 mag; for more details, see the ASPIREastro.net Inari campaign guide.

These observations involved:

• Meade 12-inch telescope
• no focal reducer, so working at f/10
• ASI 6200MM CMOS camera
• V-filter 30-sec images, then unfiltered 30-sec images, and finally unfiltered 60-sec images
• images binned 4x4
• no guiding at first, then guiding with 5-sec exposures for final group of images
• focus position on 12-inch:
  • in V: 0.224 yields FWHM 3.3 at T = 59/15 ?
  • in clear: 0.203 yields FWHM 3.0 at T = 58/14 ?

Notes from the night:

• sky clear at first, with clouds moving in after 1 AM
• no Moon at all
• camera couldn't quite reach T = -20 C at dusk, when air temp was 17 C, , so changed temp setting to T = -18 C
• started with 30-sec V-band images, didn't give enough signal to Inari. Switched to 30-sec unfiltered images, close to desired signal-to-noise. Then tried 60-sec unfiltered images. Quite a few showed some trailing, so at number 52 of the sequence "inari_b_clear", started using autoguider with 5-sec exposures. Guiding wasn't perfect, but better than no guiding.
• no animals seen in the yard

The picture below shows an image of the field of Inari on this night; The field of view is about 22 arcminutes across.

I've marked the location of several comparison stars.

  star       name                  B          V         
------------------------------------------------------
   A    TYC 832-1587-1           11.48     10.62                            
   B    TYC 832-1568-1           12.05     11.20                            
   C    TYC 832-1557-1           12.45     11.26                            
--------------------------------------------------------------------------

 

You can watch the asteroid move slowly to the north-west over the course of about 4.5 hours by clicking on the image below.

The sky background values show a jump when we changed the exposure time, and then the appearance of clouds near the end of the run.

The FWHM degraded just a bit as the night went on.