reddening: E(B-V) from interstellar Na DI lines

This package is a simple implementation of the new semi-empirical relation derived by Maxted (2025), which follows the form of Munari & Zwitter (1997) but covers the low-E(B-V) parameter space.

• Valid for stars with 0 < E(B-V) < 0.15. This corresponds to equivalent widths of roughly 0 <= EW < 0.35
• Note the definition of D1 (5895.9 Å) and D2 (5890.0 Å) used in these relations.
• The measurements with D1 and D2 lines are not independent, so if taking an average, don't reduce the error by 1/sqrt(2).

Installation

Using pip:

pip install git+https://github.com/nmiller95/reddening.git

For development:

git clone https://github.com/nmiller95/reddening.git
cd reddening
pip install -e

Usage

from reddening import D1, D2

d1 = D1(0.01)
ebv, error = d1.calculate_ebv()