How do I calibrate my telescope photometer with interstellar reddening?

[LukeKJ]

I was trying to calibrate my small telescope using a known star, but the readings from my photometer were all over the place. I realized I hadn't properly accounted for the dimming and reddening caused by interstellar dust along that line of sight.

[Ryan4]

Yeah I had a similar moment last year. I blamed the photometer until I checked how much interstellar dust was along the line of sight. The star looked dimmer and redder than it should, and the readings wandered even after repeats.

[Kenneth_A]

I did a quick cross check with a few standard stars in the same region and compared the measured colors to the published colors. The offsets lined up with the expected reddening, which explained a lot of the scatter.

[Zachary74]

Do you think the problem is just extinction and color corrections, or could there be a bigger issue with the filter set not matching the stars' spectra?

[Evelyn.J]

I ended up not trusting that calibration star alone and tried a multi star calibration, but the results still bounced when I switched nights. It felt messy.