Astronomical Visual Limiting Magnitude calculation


Brad Schaefer devised the theory [2000] and a BASIC program (To the visual limits, Sky and Telescope, May 1998, page 97), Larry Bogan translcoded the BASIC program into a web based JavaScript page and Victor Reijs made a few changes:
A further enhanced JavaScript program is available at this link.

If Goal Magnitude = 99:
The Visual Extinction Magnitude just visible with the unaided eye is calculated from conditions specified in the form below. This number depends on the location and phase of the Moon, the location of Sun, the humidity, your location and height as well as the Object's topocentric altitude.
If Goal Magnitude <> 99:
The Object's topocentric altitude when just visible with the unaided eye is calculated from conditions specified in the form below. This number depends on the location and phase of the Moon, the location of Sun, the humidity, your location and height as well as the Goal Magnitude (Magnitude of the Object). 

Try various input parameters to observe the effects of each variable. For more details see the reference sited above.

Intermediate results of astronomical extinction, sky brightness and air mass are presented in the tables at the bottom.

== DATE ==
Month Number Year
== PHASE OF THE MOON ==
New Crescent Quarter Gibbous Full
=====================================
ANGULAR POSITIONS OF SUN AND MOON

Topo.
Altitude
Azimuth
compared
to Object

MOON degrees
SUN degrees
Relative Humidity percent
Air Temperature Celsius
Latitude degrees
Height metres
Snellen Ratio 20/20=1: 20/10=2
Object's topocentric altitude degrees
Goal Magnitude magnitudes


RESULTS

Sky Brightness: nanoLamberts
Visual Extinction Magnitude: magnitudes
TopoACRV: degrees
Sun's elongation: degrees

Supplemental Results

AIRMASS
GAS AEROSOL OZONE
Extinction and Sky Brightness

U B V R I
Astromincal extinction
magnitude/air mass
Extinction magnitude
Sky Brightness picoergs/cm2/micron/arcsec
==============================
FROM "ASTRONOMICAL COMPUTING"
SKY & TELESCOPE, MAY 1998 page 52
'To the Visual Limits'
by Bradley E. Schaefer
=============================
Bogan transcoded to JavaScript and further
corrected and enhanced with the aide of
Victor Reijs

Last major content related changes: May 2, 2003