<p>I don't think an accurate formula is possible. There's always some haze, but how much, and how it scatters light,  varies. That's one of the reasons we go to space to get the best photometry.</p>

CC BY-SA 4.0
2023-12-19T17:07:06.130Z
2023-12-19T17:07:06.130Z
John Doty
<p>The <a href="https://www.eso.org/observing/etc/bin/gen/form?INS.MODE=swspectr%20INS.NAME=SKYCALC" rel="noreferrer">ESO skycalc tool</a> makes a calculation of sky brightness that incorporates many physical effects, including moonlight, starlight, zodiacal dust etc. You can get broadband magnitudes for different target-moon separations and for the moon at different phases and altitudes. It takes no account of local meteorological conditions and assumes the observer is at the Paranal site.</p>

CC BY-SA 4.0
2023-12-20T08:03:34.250Z
2023-12-20T08:09:31.853Z
2023-12-20T08:09:31.853Z
ProfRob
<p>Does anyone know if there has been any work in determining the impact of the moon on sky brightness based on phase, moon altitude (including below the horizon), location altitude, humidity, etc?  This has applications to astrophotography when deciding whether to image a target that is currently X° away from the moon at a certain phase.  There is a classic approximated 'moon avoidance' formula which can be parameterized by target-moon separation angle and moon phase to account for wavelength - e.g. narrowband vs wideband filters.  But the result doesn't differ whether the moon is above or below the horizon.  Thanks -</p>

CC BY-SA 4.0
2023-12-19T13:52:38.680Z
Providing a link to the 'classic' rule-of-thumb formula you referenced would probably improve this question.
antlersoft
CC BY-SA 4.0
2023-12-19T17:32:32.163Z
Horizons provides various information related to this. https://ssd.jpl.nasa.gov/horizons/manual.html#obsquan
PM 2Ring
CC BY-SA 4.0
2023-12-19T19:25:16.807Z
If there is one, it's probably fairly involved as the atmospheric conditions will have a lot of impact.
Greg Miller
<the-moon><photography><dark-night-sky>
Sky illumination based on moon phase and altitude
tockpeas
# Sky illumination based on moon phase and altitude

(Asked by: username_0 on 2023-12-19)

Does anyone know if there has been any work in determining the impact of the moon on sky brightness based on phase, moon altitude (including below the horizon), location altitude, humidity, etc? This has applications to astrophotography when deciding whether to image a target that is currently X° away from the moon at a certain phase. There is a classic approximated 'moon avoidance' formula which can be parameterized by target-moon separation angle and moon phase to account for wavelength - e.g. narrowband vs wideband filters. But the result doesn't differ whether the moon is above or below the horizon. Thanks -

**Tags:** the-moon, photography, dark-night-sky

> **Comments:**
> **username_1**: Providing a link to the 'classic' rule-of-thumb formula you referenced would probably improve this question.  
> **username_2**: Horizons provides various information related to this. https://ssd.jpl.nasa.gov/horizons/manual.html#obsquan  
> **username_3**: If there is one, it's probably fairly involved as the atmospheric conditions will have a lot of impact.  

---

## 2 answers

### Answer by username_4 on 2023-12-19. Score: 6

I don't think an accurate formula is possible. There's always some haze, but how much, and how it scatters light, varies. That's one of the reasons we go to space to get the best photometry.


---

### Answer by username_5 on 2023-12-20. Score: 6

The [ESO skycalc tool](https://www.eso.org/observing/etc/bin/gen/form?INS.MODE=swspectr%20INS.NAME=SKYCALC) makes a calculation of sky brightness that incorporates many physical effects, including moonlight, starlight, zodiacal dust etc. You can get broadband magnitudes for different target-moon separations and for the moon at different phases and altitudes. It takes no account of local meteorological conditions and assumes the observer is at the Paranal site.


---

