T CrB and comparison star much fainter than statet (solved)

American Association of Variable Star Observers (AAVSO)
Wed, 05/01/2024 - 18:28

Problem was an orientation issue caused by similar star patterns of comparison stars.

Visual observation of T CrB, I am a beginner. I found something weird.

I used:

  • 180mm MakCass f/15 and 38mm 2" Erfle.
  • 2024-04-30T23:30:00+02.00, Germany, Lat. 51.25°N
  • AAVSO Chart: X36498BEJ
  • Faintest star in my bright city sky in this sky area: 12m0 ± 0.2

The comparison star UCAC4-581-05220 (10m6) in the chart appears much fainter, fainter than UCAC4-580-052241(11m2), approx 11m5-11m8. All other comparison stars appeared in plausible magnitudes.

Even T CrB appeared in 11m3 ± 0.2. When I looked in the current light curves and tabular data of my observing date and time almost all visual observers transferred around 10mag to AAVSO.

I observed these stars over an hour, so no clouds or parts of it or Sahara dust (we suffer from it right now in Europe) could be the cause. I also triple checked my position and star identification.

Unfortunately the weather got worse and I have not the opportunity to verify it the next days.

Do any of you have an explanation or made similar experiences?


PS: Unfortunately I cannot upload an image with the marked star