On the night of Dec 14/15, 2023, under fair conditions, I acquired images of
All data was taken with the 12-inch telescope and ASI camera. The results were reasonable.
I also collimated the 12-inch after noticing that out-of-focus images were quite asymmetric.
I noticed a few nights ago (during a run that was aborted by clouds) that out-of-focus images taken with the 12-inch Meade looked quite asymmetric. So, I decided to start this evening's activities by tweaking the collimation of the telescope.
I began by mounting the video camera at the Cass focus of the 12-inch. Pointing the telescope at a star low in the eastern sky allows me to stand on the ladder, adjust the collimation screws on the secondary mirror, and see the results in real-time on the TV screen.
This was the appearance of an out-of-focus star at the start of the procedure (photograph taken of the TV screen):
I made three small twists (20-30 degrees each?) to the screw at the 5 o'clock position, and the image improved somewhat:
At this point, I removed the video camera from the Cass focus and replaced it with the ASI 6200MM CMOS camera. Making adjustments is more difficult, since I can't see the computer's screen from the top of the ladder, but it does allow me to modify the focus and check the FWHM after adjustments to the secondary's screws.
After making a few adjustments, the out-of-focus PSF looked like this:
It is still somewhat squished to the lower-right. I fiddled with the screws for another ten minutes and ended up with this:
When I put the camera back into focus -- and remembered to decrease the exposure time enough to prevent saturation! -- the FWHM was only 2.1 pixels. Great!
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.
These observations involved:
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. In this case, I used only stars within a "smaller" subset of the full catalog around the target, those no more than 10 arcminutes away from it. Using a catalog contains stars out to 20 arcminutes away caused the matching procedures to fail most of the time.
The target is moving to the upper-right with time, and clearly shows the back-and-forth motion due to parallax.
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:
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:
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. For this evening's data, I chose the "intermediate" subset, and restricted matches to those stars within about 11 arcminutes of the target.
Here are the positions I've measured so far. The most recent measurements are at the bottom of this plot.
