More observations of RY and Z UMa and TX and AH Dra (30th June/1st July 2022)

On Thursday night (the 30th June) we had a clear patch of weather which enabled me to make some more observations of the four variable stars I have been monitoring. It had rained heavily in the afternoon (in the form of a few torrential showers) but as evening came on the clouds began to clear away. We are still in that period of the summer when the sky never gets completely dark but going out about midnight, it is dark enough to see these 7th and 8th magnitude stars. Also the moon wasn't going to be a problem, it being only one day past new. I also had the benefit of some new 7x50 binoculars and this has made a bit of a difference in these conditions.

Starting with Z UMa again, on the chart I could make out star H quite clearly so the limiting visual magnitude was fainter than 8.7. I had no problem finding the star and it had faded since I last saw it. I determined that at 23.25 UT it was brighter than H (mag. 8.7) but fainter than D (mag. 7.9) but closer in brightness to D than H. The way of describing this technically was to record this as D(1)V(2)H. This means that the star was one "point" away from D but two "points" away from H. The difference in brightness between D and H is 0.8 magnitudes, so each point is approximately 0.8/3 = 0.27 magnitudes making Z 7.9 + 0.27 = 8.17 mag., or 8.2 to one decimal place.

RY UMa had also faded a bit since my last observation at the beginning of the month. At 23.40 UT it's brightness was between the star labelled 2 (7.4) and the star labelled 4 (7.7) but closer to 4. I recorded it as 2(2)V(1)4 making it magnitude 7.6.

Notice these times are well past midnight in British Summer Time, so I was feeling a bit tired. Nevertheless, I thought I ought to have another go at TX and AH Draconis. I started with TX as this is close to the star Eta Dra. At 00.08 UT (on the 1st July 2022) TX was brighter than N (7.7) but fainter than K (7.0). It was sort of midway in brightness between the two but marginally closer to K. I decided to record it as K(3)V(4)N which made it magnitude 7.3. 

Finally, at 00.29 UT AH was fainter than the star labelled 1 (7.1) but brighter than the star labelled 8 (8.4). In fact, it was close in brightness to the star labelled 6 (7.8). I recorded it as 1(1)V(1)8 which made it magnitude 7.8 (to one decimal place).

Comparing my observations to other observers at the BAA, the only estimate that caused me some concern over accuracy was that for TX Dra. The last few observations of this star had its magnitude around 8.0. However, looking at the AAVSO my estimate of 7.3 is close to what other observers at this association are seeing at the moment. All my observations have been loaded into the BAA database.

All text and images © Duncan Hale-Sutton 2022