I am having a problem estimating the brightness of stars using the telescope finder. When using the telescope, I do not find any problem in observation.
However, for bright stars, I estimate their brightness using the telescope finder, and I have found a variation in the brightness of stars using the finder within a few days. For example, I estimated the brightness of R Sct and its magnitude using the finder as 6.0, then after a few days I estimated it using the finder as well, and it was 5.6. I do not think that R Sct is undergoing short-term changes within days, and I do not know where the problem really is. The same thing happened with the star R Aql.
I hope you can help.
Thank you very much
what you describe is pretty normal. In some part of their cycles, these stars may vary more rapidly, e.g. when they are in the ascending branch of their light curves. 0.4 mag. in a few days is pretty common for R Sct. The star is rather irregular compared with most RV Tauris so it may change from boring to active.
If you are using the same instrument, there shouldn't be any problem.