Mean effective aperture in key numbers

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#1

I see Mean effective aperture: 6.49 m (area weighted over FOV) in Key numbers | Rubin Observatory

The next detail page Telescopes | Rubin Observatory says 6.7m. Which number is officially correct?

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#2

Thank you @youtsumi for reporting this. The effective diameter of 6.49m is the correct one. The website page Telescopes | Rubin Observatory has been updated accordingly.

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#3

Thanks, but could you clarify how did this number get calculated? The other document says 6.423m SMTN-002: Calculating LSST limiting magnitudes and SNR

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#4

When you subtract the physical area of the central hole, the camera shadow, the support structures, and the baffles from the 8.4-meter glass, the remaining physical light-collecting area is approximately 33.2 m². This is equivalent to an unobstructed circular aperture of ~6.5 meters in diameter.

I was unable to track down how we got 6.423 meters. However, if you are looking for the physical, unblocked “collecting area” of the telescope structure, you should use 6.5 meters and refer to Ivezić et al. (2019) and the Rubin DP1 paper.

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