Hi Volker,
welcome! And thanks for sharing your observations!
I am absolutely not an expert on optical observations and photometry. With this disclaimer, I believe your source 147 is dominated by the host galaxy of the transient AT 2024kbl. You can use the link to the Aladin or ESA-Sky platforms that are available in Astro-COLIBRI (web: bottom right of the screen; mobile: last screen to the right => External links) to get an overview the region from archival data. The Aladin link brings you to this page:
As you can see, the host galaxy is already rather bright. You observations certainly include light from the transient source AT 2024kbl, but I am not sure you’ll be able to tell it apart from the host emission.
To find an easier target you may want to have a look at one of the transients selected by and for amateur astronomers, in this case the RAPAS network: RAPAS observation list starting 2024-05-31
As example, the supernova SN 2024ggi is still at a V magnitude around 12.7. It is monitored extensively by amateur + professional observers. Many observations are reported to the AAVSO (the link is also available in Astro-COLIBRI). This could also be a place to share the results of your observations, i.e. the extracted photometric measurements.
All the best,
Fabian