# Why do these photometric observations of Betelgeuse look “quantized” in 0.1 magnitude steps?

The most interesting question related to this Will Kinney tweet would be what's going on with Betelgeuse? but I can't help but wonder why much but not all of the photometric data is clustered in increments of 0.1 magnitude.

These stripes were the result of posting some preliminary data where analysis had some ultimately uninteresting effect that later disappeared, but I don't think that's the case here.

So I downloaded data on Betelgeuse from @AAVSO . Here's a plot of visual magnitude vs Julian date for the last 10 years. Clearly something very strange going on -- a whole lot of anomalous dimming happening very quickly, in the last few months.

• Giant star's odd behaviour fuels speculation it's about to explode – uhoh Dec 26 '19 at 15:03
• I guess because the magnitudes are measured to the nearest 0.1 mag. Quite likely if these are just visual estimates. – ProfRob Dec 26 '19 at 15:26
• Since there's quite a few data points that also align to multiples of .25 as well, some that align to multiples of .05, and a minority that have finer resolution, I would assume that the data is taken from multiple observers. The most common type of observer just has a resolution at .1 mag. – Ghedipunk Dec 26 '19 at 21:18
• @Ghedipunk I'd definitely accept an answer like that; if these are visual and not photometric observations that makes 100% sense. I'd originally assumed they were photometric and/or there was some processing funnybusiness like this going on. – uhoh Sep 21 '20 at 3:11