The typical 5σ point-source depth in a single visit in r will be ∼24.5 (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg2 with δ<+34.5∘, and will be imaged multiple times in six bands, ugrizy, covering the wavelength range 320--1050 nm. About 90% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg2 region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to r∼27.5.

I believe 'five-sigma' refers to standard deviations in a Gaussian distribution (statistics), but am unclear what it has to do with a 'point-source depth'.

And I am even more confused by 'r' and 'lowercase-delta'....


The quote appears to be from the Ivezić et al. 2019 paper about LSST. In this context, σ quantifies the noise level in the images, and r is a photometric passband of ~620±70 nm wavelength. In single r-band images, they expect stars of AB magnitude 24.5 to stand out 5σ above the background level.

δ refers to declination; they plan to cover the sky from the south celestial pole to 34.5° north of the equator.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.