What's this dotted line?


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Moves about 0.18382’ per second, and varies in brightness regularly. Its average brightness appears to increase then decrease, peaking a bit before the middle of the line. could be a satellite, as it moves fast enough to be one, but I don’t know why it would be changing in brightness like that, as if it was rotating.

How did you guess the speed?

Satellites (or maybe space junk) can often vary in brightness like this, eg if they’re tumbling and glinting.


aha, space junk. I guessed the speed by looking at how long the trail was, that’s 25-30’ and the exposure time was 136sec

I just measured the line properly and it is 28.477’ long, so the apparent speed is 0.13586029411’/sec
I see it 42 times, so it rotates at 185.3rpm

Did you track it across all the affected chips? eg https://www.legacysurvey.org/viewer/ccd/decals-dr5/decam-346947-S11.xhtml?rect=1237,2441,100,100
(and referring to the DECam chip map, https://lh3.googleusercontent.com/proxy/IbLLYd-rdilmmliHNadfmlxL8g8TEjDs9wETTFpkwh_VA_XbhrNOV0itEUr-eqYXwk_sLvFcRrkfOPUZOdRVg0VN356uSfyo2ASOjGYSjRDGC4NyMFe_zlH0T2DMHjCj9y6XzQ)

Hmm. It only appears on S11, then there’s a gap, then it appears a bit fainter in S2. I couldn’t find it in any other images

You can see it in the bottom-right corner of S12 - CCD details for decam-346947-S12

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wait what I knew it would be going that direction, how did i not find the S12z for that date