Note added 6/24/2021: I've recalibrated the photometry to use a different reference star. The graphs haven't changed, but the datafile at end of page now has the recalibrated data.
Also, the 'new variable' has been noticed by at least one other observatory. See the entry for ASASSN-V J185704.07+164603.1 = WISEJ185704.2+164602
On the night of Jun 22/23, 2021, under good conditions, I acquired images of a new target: Nova Her 2021 = V1674 Her. One can find information about it at
This night's measurements showed a weaker signal of around 8 minutes -- but also revealed that a different, faint star in the field is an (as far as I can tell) uncatalogued variable.
This object was discovered by Seiji Ueda (Kushiro, Hokkaido, Japan) on 2021 June 12.537 UT. It rose quickly, then fell quickly.
The main setup was:
Notes from the night:
I think that meant that corrections could not be sent to the mount. The field seemed to oscillate back and forth, with a very slow drift, regardless of the Aggressiveness settings on the guider. I tried using the "Move Dialog" buttons to move the telescope manually, but that didn't appear to work either.
So, basically, this run was _not_ guided. I will check carefully on the next clear night to verify that the guider-to-telescope communications are working properly.
The object is located at
RA = 18:57:30.95 Dec = +16:53:39.6 (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. See
I'll use star "E" to shift my instrumental magnitudes to the V-band scale. It has a V-band magnitude (according to AAVSO chart X26675JQ) of 12.221, and (B-V) = 0.608.
The faint star marked "var" shows variations of size roughly +/- 0.3 mag in a roughly sinusoidal pattern over the run. It's perhaps an eclipsing binary. The star has magnitude V ~ 13.5 and position
RA = 18:57:04.13 Dec = +16:46:00.9 (J2000)
= 284.26722 = +16.76692
You can use its entry in the APASS catalog to look it up in Vizier, and to serve as a cross-reference.
The sky value shows no sign of clouds -- clear all night.
The FWHM improved when I changed the focus around midnight, then started to increase again, due to increasing airmass or change in temperature.
Using aperture photometry with a radius of 7 pixels in a V filter (binned 2x2, each pixel is 1.24 arcsec, so a radius of 8.7 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 0.007 mag with a 30-second exposures. The brightest star, "A", is slightly saturated; the outlier at instrumental mag = 3.0 is the target. The faint variable is the highest outlier around instrumemtal mag = 5.0.
Most of the changes in image-to-image zero-point are due to trailing; I discarded all images with an zeropoint of more than 10.46.
Here is the light curve of the object and several field stars in the V filter; I've shifted the instrumental magnitudes so that star "E" = 000-BMD-913 on AAVSO chart X26675JQ has the value given by AAVSO as its V-band magnitude. The faint variable star is labelled as "X".
Can we still see any of the variations with period of about 8.4 minutes? Using the Periodogram tool at the NASA Exoplanet Archive, I computed the power spectrum of these measurements. Within the top 10 peaks are some with periods of 0.00275 and 0.00540 days, which correspond to 4.0 and 7.8 minutes; however, they aren't as strong as they were in the UT Jun 17 data.
I have submitted these measurements to the AAVSO, CBA, and VSNet.
You can download my measurements below. A copy of the header of the file is shown to explain the format.
# Measurements of Nova_Her_2021 made at RIT Obs, UT 2021 Jun 23, # in good conditions, # by Michael Richmond, # using Meade 12-inch LX200 and ATIK 11000. # Exposures 30 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 7 pix = 8.8 arcseconds. # which has been shifted so AAVSO 000-BMD-913 has mag=12.221 # which is its V-band magnitude according to AAVSO. # # UT_day JD HJD mag uncert Jun23.11889 2459388.61889 2459388.62324 11.723 0.014 Jun23.11940 2459388.61940 2459388.62375 11.712 0.016 Jun23.12041 2459388.62041 2459388.62476 11.717 0.015
Last modified 6/24/2021 by MWR.