On the night of Oct 27/28, 2022, under good conditions, I acquired images of the outbursting cataclysmic variable star V515 And. These are my first observations of this target. The results were decent, so I should try to observe it again when the conditions are good (though it's likely to be too faint when the Moon is up).
I also took images of my parallax targets GX And and Ross 248.
The night was very dark, and apart from a brief period of cirrus early, mostly clear.
V515 And is a cataclysmic variable of the intermediate polar type. Good references are
The star is typically V = 15, which is pretty faint for our telescopes, with an orbital period of about 0.11 days.The main setup was:
Notes from the night:
The object is located at
RA = 00:55:19.85 Dec = +46:12:57 (J2000)
A chart of the field is shown below. The size of the chart is about 20 x 20 arcminutes.
I've marked the location of several comparison stars as well, taken from the APASS 9 catalog, or from the AAVSO's comparison list, X28280AGB.
I'll use star "F" to shift my instrumental magnitudes to the V-band scale.
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 light early clouds, but then mostly clear.
The FWHM graph below shows a very nice, small value, pretty steady.
Using aperture photometry with a radius of 5 pixels in 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 0.005 mag: very nice.
The change in zeropoint shows the early clouds.
The measurements show a gradual rise and then fall, over an interval not far from the orbital period (0.11 days).
You can download my measurements below. A copy of the header of the file is shown to explain the format.
# Measurements of V515_And made at RIT Obs, UT 2022 Oct 28, # in good 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-BJX-001 has mag=13.74 # which is its V-band magnitude according to AAVSO chart X28280AGB. # # UT_day JD HJD mag uncert Oct28.09579 2459880.59579 2459880.60040 14.867 0.023 Oct28.09660 2459880.59660 2459880.60121 14.774 0.020 Oct28.09740 2459880.59740 2459880.60201 14.750 0.020
This is one of the stars that a capstone student may study over the next year in a 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:
In order to get the best results for Ross 248, it is necessary to use only a subset of the stars in the camera's full field of view. I chose the "small" subset, which contain stars within 7 arcmin of the target, for this night.
Here are the positions I've measured so far. The most recent measurements are at bottom right.
Like Ross 248, GX And is a nearby (binary) star which will be 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.
On this night, for GX And, things were a bit unusual. The stellar images were so sharp that the usual 4-second exposure times would saturate GX And. I tried both in-focus images (exposure time 1.5 sec) and slightly defocused images (exposure time 3 sec).
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:
Using the same techniques as described for earlier nights, I matched detected stellar positions to the Gaia DR2 catalog. I used all the stars in the field.
The target is moving to the upper-right with time, and clearly shows the back-and-forth motion due to parallax.
On this night, both sets of images -- short, in-focus and longer, defocused -- yielded similar positions. In particular, these were the offsets from the fiducial position of GX And in each direction:
direction short long difference
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RA offset (mas) 6829 +/- 66 6778 +/- 64 -51 +/- 91
Dec offset (mas) 1197 +/- 60 1225 +/- 60 27 +/- 84
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That's good. It doesn't really matter at my levels of precision.