Sunday evening we had a decent patch of clear weather for me to do some observing. After carrying out some imaging, I thought I would get an estimate (with my 7x50 binoculars) for the current brightness of the variable star Z UMa which is currently near its maximum. The moon was 2 days past full and not due to rise until 22:27 UT. Twilight is now lasting much longer and Astronomical Twilight ended about 22:20 UT. Soon it will last all night.
Using BAA chart 217.02 to locate the variable, I could see (at 22:44 UT) the little triangle of stars that included H (=8.7 mag.) and Z was shining brightly nearby. I could also see (at 22:48 UT) that it was much brighter than nearby star D (=7.9 mag.). Comparing it with stars A (=6.3 mag.), B (=7.3 mag.) and C (=7.5 mag.) I couldn't really distinguish Z from B in brightness at 22:54 UT. My estimate was therefore magnitude 7.3. By that time the sky was brightening due to the rising of the moon.
All text and images © Duncan Hale-Sutton 2023
No comments:
Post a Comment