On the night of Jan 09/10, 2021, under fair conditions, I acquired images of one new target: TCP 09470380+1657350, a cataclysmic variable star which has just been detected in outburst. One can find information about it at
These are my first measurements of this star, and there are likely to be the last. It is just a bit too faint for me to make decent measurements.
This bright nova was discovered on UT 2021 Jan 07, so it was only two days old when I measured it. It's a bit too faint for me to make measurements with sufficient signal-to-noise, at a magnitude of approximately V = 15.
The main setup was:
Notes from the night:
The object is located at
RA = 09:37:03.80 Dec = +16:57:35.0 (J2000)
A chart of the field is shown below. The size of the chart is about 31 x 26 arcminutes.
I've marked the location of several comparison stars as well.
star AAVSO B V ----------------------------------------------------------- A APASS 5246287 12.311 11.879 B 000-BNT-306 14.184 13.585 -----------------------------------------------------------
I took a photo of the finder TV's screen when pointing to this target; this could be a useful reference for the future:
The sky value shows that the sky was clear. The big jump around 224.72 is due to the switch from exposure time of 30 seconds to 60 seconds.
The FWHM:
Using aperture photometry with a radius of 5 pixels in a clear filter (binned 2x2, each pixel is 1.24 arcsec, so a radius of 6.2 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 0.008 mag with a 60-second exposures, and considerably worse in 30-second exposures. The big outlier is NOT the target, but a random star which suffered from one strong cosmic ray.
Clouds moved through the sky during the observations, as these image-to-image zero-point adjustments make clear. The big jump around 224.72 is due to the switch from exposure time of 30 seconds to 60 seconds.
Here is the light curve of the object and several field stars in the clear filter; I've shifted the instrumental magnitudes so that star "B" = AAVSO 000-BNT-306 has the value given by the AAVSO as its V-band magnitude.
I have submitted measurements to the AAVSO.
You can download my measurements below. A copy of the header of the file is shown to explain the format.
# Measurements of TCP_09370380+1657350 made at RIT Obs, UT 2021 Jan 10, # in fair conditions, # by Michael Richmond, # using Meade 12-inch LX200 and ATIK 11000. # Exposures 60 seconds long, clear 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 5 pix = 6.2 arcseconds. # which has been shifted so 000-BNT-306 has mag=13.585 # which is its V-band magnitude according to AAVSO seq X25911G. # # UT_day JD HJD mag uncert Jan10.16331 2459224.66331 2459224.66816 14.947 0.044 Jan10.16376 2459224.66376 2459224.66861 14.888 0.047 Jan10.16422 2459224.66422 2459224.66907 14.942 0.041
Last modified 1/10/2021 by MWR.