On the night of Jul 06/07, 2020, under good conditions, I acquired images for astrometry of two nearby stars. One was Ross 248 , and the other GX And ; the latter is actually a double star, with two components separated by about 35 arcsec moving together.
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.
The main setup was:
Notes from the night:
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:
I ran the camera at -17 C, as it was too warm to reach the usual -20 C. Nothing out of the ordinary.
I took a series of 50 exposures of the field, using the R-band filter and an exposure time of 20 seconds.
Using the same techniques as described for earlier nights, I matched detected stellar positions to the Gaia DR2 catalog; as usual, I used a linear model and included all stars in the catalog.
I am continuing to use the box
cr=650 sc=1000 nr=1300 nc=1000mentioned in the entry for Jun 28, 2020 to avoid vignetting and coma.
This is my seventh measurement of Ross 248. I still haven't seen much motion, but that's consistent with its expected path in the sky.
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.
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 two series of 50 exposures of the field, using the R-band filter and an exposure time of only 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 direction, as we would expect from its known (large) proper motion.
I noticed a thread on the AAVSO forum discussing the possible dimming of the star KID 03644542. So, I decided to take some pictures after I'd finished with my two targets.
I took a series of 38 images, each 5 seconds long, in the R-band filter. Comparing KID to nearby stars shown in the AAVSO's chart, I determined a very rough measurement of its magnitude. I posted a note with my work to the AAVSO thread, and Sebastian Otero kindly explained that the UCAC4 measurements I'd been using as references were invalid: those are based on saturated measurements from APASS. Whoops.
However, he was able to figure out that the initial report was based on a faulty assumption -- an unnoticed close double star masquerading as a singleton. The upshot is that there is no dimming to see.
Rah?
Last modified 7/07/2020 by MWR.