Those who follow R Coronae Borealis type variables might be interested to know that AO Her appears to be fading. By my observations it’s lost over half a magnitude in the past week and is continuing to dim (currently at 12.03 TG as of about an hour ago). This might turn out to be a shallow dip down to around 12.7 or 12.8 as it experienced in the late spring or maybe it will go much deeper (it reached near magnitude 19 in 2023).
Brian (SBQ)
It still seems to be dimming, down to 12.2 (TG) just a few minutes ago. It’s lost about 0.8 magnitudes in 10 days, it will be interesting to see how much farther it goes.
Hi Brian, yes this RCB stars is coming up from a deep minimum with some kind of oscillations. This time the decline seems to be steeper than before, maybe brightness goes further down compared to the last ones.
My V measurement tonight was 12.66
It was cloudy here for a few days but last night was clear and I had it at 12.57 TG about 12 hours ago. But my TG observations are typically a little brighter than the average V reports so that doesn’t necessarily mean it’s changing course. It’s supposed to be clear here the next two nights so hopefully I can check it a few more times in the next couple of days.
Seems to go further down. Weather forcast is bad for the coming week, hope you have more luck.
Yes, by my measurement it dropped by about 0.14 magnitude between the night before last and last night, so it’s continuing to decline fairly steeply. The weather is starting to turn bad here also, but I might be able to get an observation in tonight and maybe tomorrow with luck. After that the forecast looks cloudy for a solid week.
Update on evening of 9/20 - still going down fairly steeply, down another 0.1 magnitudes since last night. I have it at 12.81 TG now.
Hi Brian.
My report. 2025/09/21 UT
Mag. 12.726, CV
Salvador (ASA)
Still dropping about a tenth of a magnitude per day, down to 12.92 (TG) about 12 hours ago. I might be able to see it again tonight but after that it looks like clouds here for almost a week 
Brian (SBQ)
It looks like it’s still dimming pretty sharply. I had it at 13.74 TG two nights ago and I see someone else put it at 13.99 V last night.
Yes, and now I have it at 14.3!
Still dropping fast; I had it at 14.84 TG last night though it was very hazy here and this was pushing the limits of my scope so there’s some uncertainty there.
Yes, I had 15.2 last night and my limit is close too (for V, but I should go on for a while…)
It’s down to around 16 now (a little above or below depending on whether it’s V or TG being reported) so there’s no sign of the fading slowing down. It still seems to be losing about a magnitude and a half per week. The lowest it’s ever been in the AAVSO database is just about magnitude 19 so it will be interesting to see how close to that it gets.
Speaking of RCB-type variables it looks like V482 Cyg has been fading steadily over the past month or so (though not nearly as steeply as AO Her). I had it at 11.27 TG last night, which is the faintest it’s been in over a year.
Brian (SBQ)
My measurement last nicht was 16.4 in V via remote telescope but SNR was only 10, error is therefore around 0.1, but certainly going down. I hope someone can observe below 17…
I tried to get an estimate last night but it’s so dim now and there were passing clouds where I am so I couldn’t get even a rough estimate with decent accuracy. I’m going to try with my astro club’s telescope later this week (the weather is supposed to be good on Thursday).
I got V=16.46 +/- 0.02 and B=17.93 +/- 0.05 for Oct 7.1 UT using the Lowell 1.1-m telescope comparing against two of the stars in the triangle just SW of the variable. Exposures 2x120s in V, 2x300s in B. Zero-point etc only ‘okay’, so subject to modest shifts.
\Brian
I tried last night but it’s beyond the reach of my set-up now. The SNR I got was only about 4 
. Just for fun I estimated it anyway and got 17.34 TG with a huge uncertainty factor.
Folks in much of the US Southwest will be out of action for several days due to unusual wet weather. Luckily the various sky surveys (ASAS-SN etc) ought to visit the field every few days, so there will be data from other sources.
\Brian
I’ve had some observations of AO Her made by one of the AAVSOnet telescopes, DSO35. It ended up dropping to around magnitude 17.5 V and has been wobbling around near there for about three weeks now. It’s getting low these days in the sky so I don’t know how much longer the observations will continue.
Brian (SBQ)