Deep-Sky Sub Length Light Pollution Check
Poisson background-variance/read-variance exposure criterion from independently measured same-filter background, not total saturation or optimal sub length. Model only, not an ephemeris, measured stellar identity or observational guarantee.
Description
Read noise and sky-background variance affect useful subexposure duration.
Read noise and sky-background variance affect useful subexposure duration.1
A chosen background-to-read-variance target is not an optimum total exposure or saturation check. Use Deep-Sky Sub Length Light Pollution Check to evaluate the supplied inputs under the model explained below.
When to use Deep-Sky Sub Length Light Pollution Check
Use Deep-Sky Sub Length Light Pollution Check to evaluate the supplied inputs under the model explained below. Establish the units, measurement scope and model assumptions before entering values.
How to use Deep-Sky Sub Length Light Pollution Check and understand its results
- Establish the units, measurement scope and model assumptions before entering values.
- Enter Read noise electrons rms, Observed background electrons per pixel per second, Caller background variance over read variance using the field table and validation rules below, then run the tool.
- Read Conditional minimum sub seconds; interpret the units, signs, ordering and unknown-value placeholders described below.
- Correct reported input errors and rerun. Apply successful results according to their specific meanings and check the assumptions before using them in a decision.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| readNoiseElectronsRms | Read noise electrons rms | number | Required; constraints below |
| observedBackgroundElectronsPerPixelPerSecond | Observed background electrons per pixel per second | number | Required; constraints below |
| callerBackgroundVarianceOverReadVariance | Caller background variance over read variance | number | Required; constraints below |
Enter nonnegative read-noise RMS in electrons, positive background electrons/pixel/s and a positive caller variance ratio. Return ratio×readNoise²/background in s; zero read noise returns zero. No exposure maximum, saturation, dark-current term or total signal-to-noise target is included.
conditionalMinimumSubSeconds=callerVarianceRatio×readNoiseRms²/backgroundRate Use the field order, units and branch conditions described above.
| Output field | Meaning | Value type |
|---|---|---|
| conditionalMinimumSubSeconds | Conditional minimum sub seconds | number |
{
"input": {
"readNoiseElectronsRms": 3,
"observedBackgroundElectronsPerPixelPerSecond": 2,
"callerBackgroundVarianceOverReadVariance": 10
},
"output": {
"conditionalMinimumSubSeconds": 45
}
}Limitations and assumptions
A chosen background-to-read-variance target is not an optimum total exposure or saturation check. Apply the exact scope and assumptions explained above.
All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse arrays fail validation. Domain-specific bounds, alignments and supported tokens are explained above; extremely large inputs or outputs can also be rejected. Input errors differ from successful false results, empty match lists and unknown-evidence placeholders.
Alternative or Complementary methods
Use Light Gathering Power vs Eye Calculator for a related task: Clear collecting area and optical throughput affect relative photon collection.
Use Rule of 500 Astrophotography Shutter for a related task: Astrophotography shutter heuristics relate focal length to a tolerance for apparent star motion.
References
Similar or alternative tools
- Light Gathering Power vs Eye Calculator
Clear collecting area and optical throughput affect relative photon collection.
- Rule of 500 Astrophotography Shutter
Astrophotography shutter heuristics relate focal length to a tolerance for apparent star motion.