ATRONOMY – ATROPHOTOGRAPHY & IMAGING (40) CALCULATOR
Atmospheric Refraction
A precise tool.
What is the Atmospheric Refraction & How does it work?
Atmospheric refraction bends light as it passes through Earth’s atmosphere, causing celestial objects to appear higher than their true geometric position. The effect is strongest near the horizon where the light path traverses the densest layers of air.
The amount of refraction depends on the apparent altitude of the object, as well as local atmospheric conditions such as temperature, pressure, and humidity. Warmer, less dense air reduces refraction, while higher pressure and humidity increase it.
For practical astrophotography, correcting for refraction improves the accuracy of plate solving and alignment, especially when framing low‑altitude targets. The following empirical formula provides a good approximation for refraction in arcminutes.
R = frac{1.02}{tanleft(left(alpha + frac{10.3}{alpha+5.11}right)frac{pi}{180}right)} cdot frac{P}{1010} cdot frac{283}{273+T}
R = refraction (arcminutes), alpha = apparent altitude (°), P = pressure (hPa), T = temperature (°C)
Parameters
Result
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Frequently Asked Questions
What is atmospheric refraction?
Atmospheric refraction is the bending of light as it passes through Earth’s atmosphere, causing celestial objects to appear higher than their true position.
How does temperature affect atmospheric refraction?
Warmer temperatures result in less dense air, which reduces atmospheric refraction. Cooler temperatures lead to denser air and increased refraction.
What is the strongest effect of atmospheric refraction?
The effect is strongest near the horizon where light travels through more layers of Earth’s atmosphere.
How does humidity impact atmospheric refraction?
Higher humidity increases atmospheric refraction because moist air is denser than dry air.
Can you explain how pressure affects atmospheric refraction?
Higher atmospheric pressure leads to increased refraction as the air becomes more compressed and dense.
Why do celestial objects appear higher in the sky due to refraction?
Light from celestial objects bends as it enters Earth’s atmosphere, causing them to appear higher than their actual position above the horizon.
Is atmospheric refraction more noticeable during certain times of day?
Yes, refraction is most noticeable near sunrise and sunset when celestial objects are closer to the horizon.
Results are for informational purposes only and do not constitute professional advice.