Photon and CCD noise budget
For independent Poisson source, sky and dark counts and independent read noise, an aperture-summed CCD measurement has variance S+B+D+nₚNᵣσᵣ².
Key knowledge
For independent Poisson source, sky and dark counts and independent read noise, an aperture-summed CCD measurement has variance S+B+D+nₚNᵣσᵣ². Its model signal-to-noise ratio is S divided by the square root of that variance. Longer total exposure and the number of readouts affect different terms.
Values and equations
SNR = S/√(S+B+D+nₚNᵣσᵣ²)
- S,B,D
- expected source, sky and dark electron counts electron counts
- nₚ,Nᵣ
- aperture pixel and readout counts 1
- σᵣ
- read-noise standard deviation per pixel/readout electron counts
- SNR
- model signal-to-noise ratio 1
Conditions and scope
- S,B,D are expected electron counts over the same aperture and complete exposure; σᵣ is the standard deviation per pixel per readout.
- This ideal budget omits uncertainty in estimating the background, flat-field errors, correlated pixels and other systematic effects; include them when relevant. A fixed SNR is not a universal detection decision rule.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the source/sky/dark Poisson and summed read-noise equations and limiting exposure cases. Corrected the sky-rate symbol and dark-rate time-unit inconsistency; excluded dated efficiencies, instrument performance and universal SNR thresholds.
2026-10-10 · Independent AI editorial review: All44 exact root-authored compact records, equations/variable units/conditions and140 origin edges accepted after independently reading final6/18 with bounded primary bodies and matching prior38/122 scientific fingerprints unchanged. Exact claim/edge review is distinct from combined inventory scope and separate CLE26 approval; no entire cited books or old-corpus experimental revalidation is asserted. Receipt: cosmos-completion-independent-content-and-inventory-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- uni-cosmos-ccd-noise-budget
- Revision
- core.1
- Structured reference record
- University core expansion