Astronomy Magnitude Flux Ratio

Written by Aarav Sharma, Mathematics Editor Reviewed by Vikram Sen, Technical Reviewer Last updated: June 1, 2026 Last verified: June 1, 2026 · Methodology · Accuracy policy

A photometry conversion KPI. Distinct from distance modulus.

Flux ratio = 10 to the power of (−0.4 × magnitude difference).

Tip: Keep “Magnitude m1” and “Magnitude m2” on the same basis (period, units, and population) before calculating Astronomy Magnitude Flux Ratio.

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Pogson’s magnitude scale converts a magnitude difference into a flux ratio.

Enter magnitudes m1 and m2 for the same bandpass.

Flux Ratio F1/F2

Understanding Astronomy Magnitude Flux Ratio

How we calculate. Flux ratio = 10 to the power of (−0.4 × magnitude difference). The form uses the same arithmetic as the worked examples on this page. See our methodology and accuracy policy.

Real-world scenario: A typical Astronomy Magnitude Flux Ratio case uses magnitude m1 1 and magnitude m2 6. Enter the same figures below to reproduce the worked path.

What is Astronomy Magnitude Flux Ratio?

A photometry conversion KPI. Distinct from distance modulus.

Same band
Brighter = smaller magnitude
Ratio dimensionless

The Formula

Magnitude Flux Ratio

F1/F2 = 10^(−0.4 × (m1 − m2))

Worked Example

Scenario: m1 = 1; m2 = 6.

Step 1: Δm = −5

Step 2: −0.4 × (−5) = 2

Step 3: 10² = 100

Answer: Flux ratio F1/F2 is 100.

Common Use Cases

Homework: Pogson scale
Lab: relative photometry
Study: pair with distance modulus

Pro Tips

m1 brighter ⇒ ratio > 1
Don’t mix filters
Not a distance tool

Limitations: Astronomy Magnitude Flux Ratio results are educational astronomy study aids—not navigation, mission planning, or professional observing advice. Confirm constants and units with your textbook or instructor.

FAQ

Why −0.4?

Because 5 magnitudes is a factor of 100 in flux: 10^(0.4×5) = 100.

Same as redshift?

No—this converts magnitudes to flux ratio only.

Authoritative References

For astronomy study concepts, consult:

OpenStax Astronomy — free textbook reference
NASA — mission and outreach context
IAU — astronomical constants and naming