On the night of Aug 02/03, 2019, Evan Muskopf and 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 amplitude of variation continues to decrease, now only about 0.07 or 0.08 mag, and the mean magnitude has faded to V=11.80.
Mike Zemcov and his students came to the observatory to place the CSTARS instrument on our 14-inch telescope's mount, so that they could acquire images of stars under different conditions.
NASA is funding the CIBER-2 rocket-launched space telescope mission, which will study the light from very distant galaxies. In order to understand the data collected by the telescope during its flight, scientists must know exactly where it was pointing. Professor Mike Zemcov, of RIT's School of Physics and Astronomy, is leading the effort to build a "star tracker:" a small telescope and camera which will detect stars and match their positions to known stars in catalogs. This star-tracking instrument is known as CSTARS.
This evening, Zemcov and some of his students brought their instrument to the Observatory for some real-world experience. Our plan was to place it on the Astrophysics mount in the rolloff building, which normally holds our 14-inch Celestron telescope. The instrument could then acquire images of stars with the tracking turned on and turned off; we could also take data while slewing the telescope at some known rate and direction.
Below are a few pictures from the session, which was successful in acquiring test images. Click on an image for a full-sized version (5 times larger in each dimension).
The main setup was:
Notes from the night:
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 ----------------------------------------------------
When the telescope is pointed at the field, the finder scope's image on the television screen looks like this (North up, East left):
The dark current was a bit higher than usual -- as we worked at T = -18 C instead of the usual -20 C.
The sky value shows the brief period of clouds clearly.
Here's a record of the telescope's drift. Note the poor performance in the second half of the night. Could this be due to a taut cable from the finder TV camera?
The number of objects detected.
I used an aperture with radius 4.0 pixels.
I tried to remove images affected by clouds; looks like I managed to do so pretty well.
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 in a 600x600 pixel box around the target 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 0.007 mag overall, which is good. I marked the brightest two stars in the ensemble as "variable," due to saturation.
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 Aug 3, # in fair conditions, # by Michael Richmond and Evan Muskopf, # using Meade 12-inch LX200 and ATIK 11000. # Exposures 20 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 Aug03.08213 2458698.58213 2458698.58467 11.825 0.009 Aug03.08251 2458698.58251 2458698.58505 11.841 0.009
Last modified 8/12/2019 by MWR.