On the night of Jul 20/21, 2019, I acquired a set of observations of the newly discovered WV Sge cataclysmic variable star TCP J21040470+4631129 (see also Astronomer's Telegram 12947 ).
The filterwheel continues to make trouble; it didn't work properly, for the most part, until it did.
The main setup was:
Notes from the night:
When one first cycles power to filterwheel, it makes 2 complete revolutions, then moves an extra 2-4 spaces, and stops with one filter centered in front of CCD.
However, after plugging/unpluggling/replugging many times, and starting/restarting MaximDL, the filterwheel suddenly _did_ work properly, putting the requested filter into the proper position. Strange.
The object is located at
RA = 21:04:04.7 Dec = +46:31:12.9
A chart of the field is shown below. The size of the chart is about 21 by 15 arcminutes.
I've marked the location of several comparison stars, which also appear in light curves below.
star UCAC4 B V ---------------------------------------------------- A 683-095755 10.832 10.528 B 683-095722 11.142 10.948 C 683-095772 12.342 10.960 D 683-095866 12.814 12.414 E 683-095811 14.017 12.691 ----------------------------------------------------
The dark current looked like this:
The sky value shows a smooth decrease; no clouds.
Here's a record of the telescope's drift. I made no adjustments to the mount during the night.
The number of objects detected -- I required 300 objects for an image to be included in the ensemble.
I used an aperture with radius 4.0 pixels. I made no changes to focus.
I discarded images which had fewer than 300 stars.
Using aperture photometry with a radius of 4 pixels (binned 2x2, each pixel is 1.34 arcsec, so a radius of 5.4 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 was about 0.009 mag overall, better than the 0.013 of Jul 18; increasing exposure time from 10 to 15 seconds did help to improve the signal-to-noise. Good. I marked the brightest three stars in the ensemble as "variable," due to saturation. The outliers in the figure below are due to single image defects.
Here are light curves of the variable and the field stars.
I used the UCAC value for the V-band magnitude of star "A" = UCAC4 683-095755 to shift the ensemble magnitudes to the standard V-band scale.
Here's a closeup of the variable and stars of similar magnitude.
You can download my measurements below. A copy of the header of the file is shown to explain the format.
# Measurements of TCPJ21040470+4631129 made at RIT Obs, UT 2019 Jul 21, # in good conditions, # by Michael Richmond, # using Meade 12-inch LX200 and ATIK 11000. # Exposures 15 seconds long, V filter. # Tabulated times are midexposure (FITS header time - half exposure length) # and accurate only to +/- 1 second (??). # 'mag' is a differential magnitude based on ensemble photometry # using a circular aperture of radius 4 pix = 5.3 arcseconds. # which has been shifted so UCAC4 683-095755 has mag=10.528 # which is its V-band magnitude according to UCAC4. # # UT_day JD HJD mag uncert Jul21.10271 2458685.60271 2458685.60484 10.653 0.010 Jul21.10304 2458685.60304 2458685.60517 10.656 0.009 Jul21.10337 2458685.60337 2458685.60550 10.640 0.010
Last modified 7/21/2019 by MWR.