Astronomical seeing describes the blurring of celestial objects caused by atmospheric turbulence. The angular size of the seeing disc, (theta), depends on the observing wavelength, generally improving (smaller (theta)) at longer wavelengths because the Fried parameter (r_0) scales as (lambda^{6/5}).
This wavelength dependence can be expressed as (theta(lambda) = theta_{text{ref}} left(frac{lambda}{lambda_{text{ref}}}right)^{-1/5}), where (theta_{text{ref}}) is the measured seeing at a known reference wavelength (lambda_{text{ref}}). By rearranging the relation you can predict the seeing at any other wavelength or, conversely, determine which wavelength will give a target seeing.
Solving the equation for the wavelength that yields a desired seeing (theta_{text{best}}) gives the βbestβseeing wavelengthβ. This is useful for planning astrophotography sessions, especially when selecting filters or exposure settings to match the atmospheric conditions.
\lambda_{\text{ref}} = reference wavelength (nm)
\theta_{\text{ref}} = seeing at reference wavelength (arcsec)
\theta_{\text{best}} = desired seeing (arcsec)
What is the relationship between observing wavelength and atmospheric seeing?
How does the formula ΞΈ(Ξ») = ΞΈ_ref (Ξ»/Ξ»_ref)^(-1/5) work?
Why is the Fried parameter important in this calculation?
Can you explain what the seeing disc is in astronomy?
How does wavelength affect the resolution of astronomical observations?
What is the significance of ΞΈ_ref in the formula?
How can this calculator help astronomers plan their observations?
Results are for informational purposes only and do not constitute professional advice.