On the night of Oct 31/Nov 01, 2020, under fair conditions, I acquired some images of the dwarf nova V392 Per, which has been identified by Joe Patterson of the CBA as a good target. In addition, I acquired images of the nearby stars Ross248 and GX And to continue the astrometric project of one of our students at RIT.
I wanted to try to capture the rapid variations of the near-Earth object 2020 UG6, but it was too close to the Moon -- just 5 degrees or so. Rats!
You can find some basic information on this star at SIMBAD.
The main setup was:
Notes from the night:
I started guiding on one star, but it seemed perhaps a bit faint; so I moved to a brighter guide star, which should been fine in 5-second exposures. However, the guide software couldn't find it in many images. I tried 10-second exposures, but the software wasn't finding the star at all. I think something was messed up with the software -- I may have closed a window or resized it somehow, which ruined the software's knowledge of where the star was in the frame. One clue: the guider's little box of pixels was shown inside a large window, instead of being shown in a small window just large enough to fit it. I hope the guider goes back to normal behavior next time.
The object is at
RA = 04:43:21.37 Dec = +47:21:25 (J2000)
A chart of the field based on pictures previously taken is shown below. The size of the chart is about 20 x 20 arcminutes.
The chart below is from the AAVSO; see their full table with more information.
For the measurements reported in the text file below, I used the star labelled "A" in my chart to calibrate the measurements to the V-band, using APASS as the source of the V-band mag.
Here's a picture of the TV with the finder's field of view when pointing at V392 Per:
The dark current was the same as usual -- good.
The FWHM varied from 4-5 pixels (= 5-6 arcsec) over the run. Although the target is only 8 pixels = 10 arcsec from a nearby star, I used an aperture with a 4 pixel = 5 arcsec radius.
Clouds were appeared briefly near the end, left, and then came back for good.
The graph of image zero-points shows three outliers near the middle, due to my fiddling with the guiding.
Using aperture photometry with a radius of 4 pixels (binned 2x2, each pixel is 1.25 arcsec, so a radius of 5 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 0.006 mag, which is not great. I marked the saturated stars as variable, so they would not affect the solution. Both of the outliers around mag = 5 are spurious; V392 Per does not rise about the typical scatter at its mag.
Here are light curves of the variable and the field stars.
You can download my measurements below. A copy of the header of the file is shown to explain the format.
# Measurements of V392_Per made at RIT Obs, UT 2020 Nov 1, # in fair conditions, # by Michael Richmond, # using Meade 12-inch LX200 and ATIK 11000. # Exposures 40 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 4 pix = 5.0 arcseconds. # which has been shifted so TYC 3347-1110-1 has mag=11.409 # which is its V-band magnitude according to APASS. # # UT_day JD HJD mag uncert Nov01.26302 2459154.76302 2459154.76718 14.668 0.042 Nov01.26360 2459154.76360 2459154.76776 14.623 0.041 Nov01.26418 2459154.76418 2459154.76834 14.700 0.041
This is one of the stars that a capstone student is studying for his project involving parallax. Ross 248 is a relatively faint red star surrounded by many other stars of similar brightness, so it's a good candidate for high-precision parallax measurements.
These observations involved:
The object is (currently) near position
RA = 23:41:55.27 Dec = +44:10:06.38 (J2000)
A chart of the field is shown below. The size of the chart is about 41 x 27 arcminutes. The noisy area at right (West) is the shadow of the guider's pickoff mirror.
I've marked the location of several comparison stars.
star UCAC4 B V r ------------------------------------------------------------------------- A UCAC4 671-120730 12.617 10.689 B UCAC4 671-120688 C UCAC4 671-120749 10.987 10.663 P kappa And 4.06 4.14 --------------------------------------------------------------------------
I took a photo of the finder TV's screen when pointing to Ross 248; this could be a useful reference for the future:
The sky value shows no clouds, just rising sky as the target set.
The number of objects detected.
Here are the positions I've measured so far. Note the clear motion to the south-east (lower-left).
Like Ross 248, GX And is a nearby (binary) star which is the target of a parallax project in the coming year. One of the two components is bright -- about mag V = 8 -- so one must use short exposures to prevent it from saturating the detector. That may mean that this system isn't as easy to measure as Ross 248 or some others.
The object is currently close to this position:
RA = 00:18:28.4 Dec = +44:01:31 (J2000)
but it does have a very high proper motion.
A chart of the field is shown below. The size of the chart is about 41 x 27 arcminutes. The noisy area at right (West) is the shadow of the guider's pickoff mirror.
The two components of the GX And binary sit inside the box. I've marked the location of several comparison stars as well.
star UCAC4 B V r ----------------------------------------------------------- A 671-001473 9.939 9.790 B 670-001639 9.413 8.472 C 671-001509 12.712 11.421 11.001 -----------------------------------------------------------
I took a photo of the finder TV's screen when pointing to GX And; this could be a useful reference for the future:
I took a total of 50 exposures of the field in R-band, using exposure times of 5 seconds.
Using the same techniques as described for earlier nights, I matched detected stellar positions to the Gaia DR2 catalog.
The target is clearly moving in the positive RA and Dec directions, as we would expect from its known (large) proper motion.
Last modified 11/01/2020 by MWR.