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Comment by thaumasiotes | Hacker News Reader

> For 100 hours, between Dec. 18 and 28, Hubble stared at a patch of sky near the Big Dipper’s handle that was only about 1/30th as wide as the full moon. In total, the telescope took 342 pictures of the region, each of which was exposed for between 25 and 45 minutes.

How did this work? 342 pictures at 25 minutes each is already well over 100 hours. At 45 minutes, it'd be 256 hours.

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Possibly counting images using different sensors as separate exposures, even if they're taken during overlapping time intervals

The Hubble Telescope has multiple cameras and sensors.

Indeed, the math doesn't pencil out.

I don't know, but I'd hazard a guess that the image is 100 hr deep on multiple tiles.

The dataset spans 10 days, which is 240 hr.

The telescope's orbital period and the relative positions of the earth and the sun will affect how the exposures are scheduled.

I went looking for more detailed information -- It appears they are open enough with the data that you can see exactly how the exposures were taken. Assuming what I found is right and that someone could make sense of the data. There are postscript files listing activity for each of the 10 days, but I am not exactly sure what we're looking at.

https://www.stsci.edu/ftp/science/hdf/project/project.html

Here you go:

https://www.stsci.edu/ftp/science/hdf/project/scheduling.htm...

Observations run from 352:16 to 362:19.

Filter Nexp hours

F300W 100 48.93

F450W 62 36.52

F606W 77 34.94

F814W 49 34.86

Could it be 100hrs of night sky?

That makes no sense for a satellite in orbit around the earth outside of the atmosphere. It would never point at the sun. The only issue is that the earth would periodically occlude the area of observation.

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