Procedures to determine the visibility of objects. More...

Functions/Subroutines
subroutine	best_planet_xsmag (jdin, plid, jdout, xsmag, rscwarn)
	Find the moment (JD) of optimal excess magnitude for a planet, i.e. the lowest mag - lim.mag.

real(double) function	best_planet_visibility (jd, pl)
	Find a rough indication for the best moment (JD) to observe a planet on a given day (jd). Start out by demanding that Sun alt < -6deg, but relax this if problematic. This often results in the moment where Sun alt is indeed -6deg.

subroutine	planet_visibility_tonight (jd, pl, sunalt, plalt, comp, plvis, plazs, rts, tts, sts, ras, tas, sas, rscwarn)
	Compute when a given planet is visible in a given night.

logical function	comet_invisible (jd, cometid, mlim, minalt)
	Cheap function to determine whether a comet is invisible at a given time, based on a magnitude and altitude limit.

real(double) function	transitalt (lat, dec)
	Compute the transit altitude of an object with given declination for an observer with a given geographic latitude.

subroutine	best_obs_date_ra (year, ra, accuracy, mon, dy)
	Compute the best date in the year to observe an object with a given right ascension.

real(double) function	get_dra_obj (jd)
	Compute the difference between a given right ascension and the RA of the Sun, used privately by best_obs_date_ra()

real(double) function	airmass (alt)
	Compute the airmass for a celestial object with a given TRUE altitude.

real(double) function	airmass_la (alt)
	Compute the airmass for a celestial object with a given apparent altitude; low-accuracy alternative for airmass()

real(double) function	extinction_magpam (ele)
	Compute the extinction in magnitdes per unit airmass for an observer with given elevation.

real(double) function	extinction_mag (alt, ele)
	Compute the extinction in magnitdes for an observer with given elevation and an object with given TRUE altitude.

real(double) function	extinction_fac (alt, ele)
	Compute the extinction factor for an observer with given elevation and an object with given altitude.

real(double) function	limmag_full (year, month, obselev, obslat, sunalt, sunelon, moonphase, moonalt, moonelon, objalt, humid, airtemp, snrat, verbosity)
	Calculate limiting magnitude based on Sun and Moon positions and phase, and on the altitude of the observed object.

subroutine	limmag_extinction (month, obslat, obselev, objalt, relhum, temp, band1, band2, extcoef, extmag)
	Calculate limiting magnitude based on Sun altitude and Moon phase.

subroutine	limmag_skybrightness (year, sunalt, sunelon, moonphase, moonalt, moonelon, objalt, band1, band2, extcoef, skybr)
	Calculate sky brightness based on Sun altitude and Moon phase.

real(double) function	limmag_jd (jd, objra, objdec, objalt, lat, height)
	Calculate limiting magnitude based on JD and object altitude, wrapper for limmag_full()

real(double) function	limmag_zenith_jd (jd, lat, lon, height)
	Calculate limiting magnitude for the local zenith, based on JD and observer's location.

real(double) function	limmag_jd_pl (jd, pl)
	Calculate limiting magnitude based on JD and planet ID, wrapper for limmag_jd()

real(double) function	limmag_sun_airmass (month, sunalt, sunaz, objalt, objaz, lat, height)
	Calculate limiting magnitude based on Sun altitude and object altitude (airmass). Assumes New Moon.

real(double) function	limmag_sun (sunalt)
	Calculate limiting magnitude, based on the altitude of the Sun. Simplified version of limmag_full()

real(double) function	pl_xsmag (jd, pl)
	Compute the excess magnitude for planet pl at JD, considering Sun, Moon and airmass.

real(double) function	pl_xsmag_pl (jd)
	Compute the excess magnitude at JD, wrapper for pl_xsmag() for solvers. The planet ID pl0 is passed through module planetdata.

real(double) function	pl_xsmag_la (jd, pl)
	Compute the excess magnitude for planet pl at JD, considering airmass and Sun alt - low-accuracy version of pl_xsmag()

real(double) function	pl_xsmag_la_pl (jd)
	Compute the excess magnitude at JD, wrapper for pl_xsmag_la() for solvers. The planet ID pl0 is passed through module planetdata.

real(double) function	aperture (xsmag, pupil, tc)
	Aperture diameter in centimetres needed to observe an object with given excess magnitude (0: no instrument needed)

elemental real(double) function	skybrightness_mas2_from_mlim (mlim)
	Convert naked-eye visual limiting magnitude (V) to sky surface brightness in (B) magnitudes per square arcsecond.

elemental real(double) function	skybrightness_mlim_from_mas2 (skybright)
	Convert sky surface brightness in (B) magnitudes per square arcsecond to naked-eye visual limiting magnitude (V)

elemental real(double) function	skybrightness_mlim_from_cdm2 (cdm2)
	Convert sky brightness in candela per square meter to naked-eye visual limiting magnitude (V)

elemental real(double) function	skybrightness_cdm2_from_mlim (mlim)
	Convert limiting visual magnitude to sky brightness in candela per square meter.

elemental real(double) function	skybrightness_cdm2_from_nl (nl)
	Convert sky brightness in nanolambert to candela per square meter.

elemental real(double) function	skybrightness_nl_from_cdm2 (cdm2)
	Convert sky brightness in candela per square meter to nanolambert.

Detailed Description

Procedures to determine the visibility of objects.

Function/Subroutine Documentation

◆ airmass()

real(double) function thesky_visibility::airmass ( real(double), intent(in) alt )

Compute the airmass for a celestial object with a given TRUE altitude.

Parameters

alt	TRUE altitude of object (radians)

Return values

airmass The airmass (-)

Note

Results are 1 <= airmass <~ 38.35; return ~1000 for h<-34'
Maximum supposed error (at the horizon) of 0.0037 air mass

See also: Young (1994); https://en.wikipedia.org/wiki/Air_mass_%28astronomy%29#Interpolative_formulas

Definition at line 539 of file visibility.f90.

References airmass().

Referenced by airmass(), extinction_mag(), thesky_daylight::extinction_sun(), and pl_xsmag_la().

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◆ airmass_la()

real(double) function thesky_visibility::airmass_la ( real(double), intent(in) alt )

Compute the airmass for a celestial object with a given apparent altitude; low-accuracy alternative for airmass()

Parameters

alt	Apparent altitude of object (radians)

Return values

airmass_la The airmass (-)

Note

Results are 1 <= airmass <~ 37.92; return ~1000 for h<0

See also: Kasten and Young (1989); http://en.wikipedia.org/wiki/Airmass_%28astronomy%29#Interpolative_formulas

Definition at line 573 of file visibility.f90.

References airmass_la().

Referenced by airmass_la().

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◆ aperture()

real(double) function thesky_visibility::aperture	(	real(double), intent(in)	xsmag,
		real(double), intent(in), optional	pupil,
		real(double), intent(in), optional	tc )

Aperture diameter in centimetres needed to observe an object with given excess magnitude (0: no instrument needed)

Parameters

xsmag	Excess magnitude: magnitude of an object MINUS limiting magnitude (>0: too weak for naked eye)
pupil	Pupil diameter (mm, default: 6)
tc	Transmission coefficient of the instrument (default: 0.8 = 80%)

Return values

aperture The aperture diameter (cm)

Note: This routine should be used as an indication only - no hard facts...

See also

http://iovs.arvojournals.org/article.aspx?articleid=2161149 - Fig.3a
- average pupil diameter at low light: 7 -> 5mm for 20- -> 80-year olds
- use 6mm as default value
http://www.telescope-optics.net/functions.htm
- default tc for amateur telescopes: ~80%

Definition at line 1341 of file visibility.f90.

References aperture().

Referenced by aperture().

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◆ best_obs_date_ra()

subroutine thesky_visibility::best_obs_date_ra	(	integer, intent(in)	year,
		real(double), intent(in)	ra,
		integer, intent(in)	accuracy,
		integer, intent(out)	mon,
		integer, intent(out)	dy )

Compute the best date in the year to observe an object with a given right ascension.

Parameters

year	Year (CE)
RA	Right ascension of the object
accuracy	Get an accurate (but more expensive) result: 0-no, 1-yes
mon	Month of year (output)
dy	Day of month (output)

Definition at line 462 of file visibility.f90.

References get_dra_obj().

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◆ best_planet_visibility()

real(double) function thesky_visibility::best_planet_visibility	(	real(double), intent(in)	jd,
		integer, intent(in)	pl )

Find a rough indication for the best moment (JD) to observe a planet on a given day (jd). Start out by demanding that Sun alt < -6deg, but relax this if problematic. This often results in the moment where Sun alt is indeed -6deg.

Parameters

jd	Julian day to compute best moment for
pl	Planet to compute visibility for (0-Moon, 1-Mercury, etc.)

Return values

best_planet_visibility Best moment to observe the planet (JD)

Definition at line 125 of file visibility.f90.

References best_planet_visibility(), thesky_planetdata::nplanpos, thesky_planets::planet_position(), thesky_planetdata::planpos, thesky_riset::riset(), and thesky_local::tz.

Referenced by best_planet_visibility().

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◆ best_planet_xsmag()

subroutine thesky_visibility::best_planet_xsmag	(	real(double), intent(in)	jdin,
		integer, intent(in)	plid,
		real(double), intent(out)	jdout,
		real(double), intent(out), optional	xsmag,
		logical, intent(in), optional	rscwarn )

Find the moment (JD) of optimal excess magnitude for a planet, i.e. the lowest mag - lim.mag.

Parameters

jdin	Initial guess for the moment of best excess magnitude (input)
plID	Planet to compute visibility for (0-Moon, 1-Mercury, etc.)
jdout	Moment of best excess magnitude (output)
xsmag	Excess magnitude at that moment (magnitude - limiting magnitude; <0: ~visible to the naked eye) (output, optional)
rsCWarn	Print convergence warnings in riset() (input, optional; default = true)

Definition at line 76 of file visibility.f90.

References thesky_datetime::gettz(), thesky_planetdata::pl0, pl_xsmag_pl(), and planet_visibility_tonight().

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◆ comet_invisible()

logical function thesky_visibility::comet_invisible	(	real(double), intent(in)	jd,
		integer, intent(in)	cometid,
		real(double), intent(in)	mlim,
		real(double), intent(in)	minalt )

Cheap function to determine whether a comet is invisible at a given time, based on a magnitude and altitude limit.

Parameters

jd	Julian day for calculation
cometID	Comet ID
mlim	Maximum magnitude, below which the comet is defined as visible (deg)
minalt	Minimum transit altitude, above which the comet is defined as visible (deg)

Return values

comet_invisible Comet is invisible (true/false)

Note: The comet may still be invisible if comet_invisible=.false., e.g. when it's too close to the Sun

Definition at line 391 of file visibility.f90.

References comet_invisible(), thesky_cometdata::cometdiedatp, thesky_cometdata::cometelems, thesky_comets::cometgc(), thesky_coordinates::ecl_2_eq(), thesky_local::lat0, thesky_planetdata::planpos, and transitalt().

Referenced by comet_invisible().

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◆ extinction_fac()

real(double) function thesky_visibility::extinction_fac	(	real(double), intent(in)	alt,
		real(double), intent(in), optional	ele )

Compute the extinction factor for an observer with given elevation and an object with given altitude.

Parameters

alt	Altitude of object (radians)
ele	Evelation of the observer above sea level (metres; optional)

Return values

extinction_fac Extinction factor (-)

Note

- extinction_fac = 1: no extinction, extinction_fac > 1 extinction.

Hence, the flux, corrected for extinction, should be f' = f / extinction_fac(alt,ele)
Assumed is the response of the rods in the human retina, hence night vision

See also: function extinction_mag()

Definition at line 671 of file visibility.f90.

References extinction_fac(), and extinction_mag().

Referenced by extinction_fac().

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◆ extinction_mag()

real(double) function thesky_visibility::extinction_mag	(	real(double), intent(in)	alt,
		real(double), intent(in), optional	ele )

Compute the extinction in magnitdes for an observer with given elevation and an object with given TRUE altitude.

Parameters

alt	Altitude of object (radians)
ele	Evelation of the observer above sea level (metres; optional)

Return values

extinction_mag Extinction (magnitudes)

Note

- The magnitude of an object corrected for airmass should be m' = m + extinction_mag(alt,ele)

Assumed is the response of the rods in the human retina, hence night vision

See also: Functions extinction_magPam() and airmass()

Definition at line 640 of file visibility.f90.

References airmass(), extinction_mag(), and extinction_magpam().

Referenced by extinction_fac(), and extinction_mag().

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◆ extinction_magpam()

real(double) function thesky_visibility::extinction_magpam ( real(double), intent(in) ele )

Compute the extinction in magnitdes per unit airmass for an observer with given elevation.

Parameters

ele	Evelation of the observer above sea level (metres)

Return values

extinction_magPam Extinction (magnitdes per unit airmass)

Note

The magnitude of an object corrected for airmass should be m' = m + extinction_magPam(ele) * airmass(alt) (see function extinction_mag())
This assumes night vision, using the rods in the human eye's retina. Hence, this will not hold for the Sun! (There is some correspondence when only considering ~420-580 nm, which is roughly the sensitivity band of the rods.)

See also: Green, ICQ 14, 55 (1992), http://www.icq.eps.harvard.edu/ICQExtinct.html, (for lambda=510 nm!), based on Hayes & Latham, ApJ 197, 593 (1975): http://esoads.eso.org/abs/1975ApJ...197..593H (wavelength dependent, for Wega)

Definition at line 610 of file visibility.f90.

References extinction_magpam().

Referenced by extinction_mag(), extinction_magpam(), and pl_xsmag_la().

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◆ get_dra_obj()

real(double) function thesky_visibility::get_dra_obj ( real(double), intent(in) jd )

Compute the difference between a given right ascension and the RA of the Sun, used privately by best_obs_date_ra()

Parameters

jd	Julian day

Return values

get_dRA_obj Difference between a given right ascension and the RA of the Sun (rad)

Note

Get (RA_obj - RA_sun) for object with RA ra, passed via the common block best_obs_RA

Definition at line 507 of file visibility.f90.

References get_dra_obj(), thesky_planets::planet_position(), and thesky_planetdata::planpos.

Referenced by best_obs_date_ra(), and get_dra_obj().

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◆ limmag_extinction()

subroutine thesky_visibility::limmag_extinction	(	integer, intent(in)	month,
		real(double), intent(in)	obslat,
		real(double), intent(in)	obselev,
		real(double), intent(in)	objalt,
		real(double), intent(in)	relhum,
		real(double), intent(in)	temp,
		integer, intent(in)	band1,
		integer, intent(in)	band2,
		real(double), dimension(5), intent(out)	extcoef,
		real(double), dimension(5), intent(out)	extmag )

Calculate limiting magnitude based on Sun altitude and Moon phase.

Parameters

month	Month of observation (for approximate Sun RA)
obsLat	Latitude of the observed (rad)
obsElev	Elevation of the observer (m)
objAlt	Altitude of the observed object (rad)
relHum	Relative humidity
temp	Air temperature
band1	First of UBVRI bands to compute (1-5); compute band1-band2
band2	Last of UBVRI bands to compute (1-5); compute band1-band2
extCoef	Atmospheric extinction for UBVRI (output)
extMag	Delta magnitude due to atmospheric extinction for UBVRI (output)

See also: BASIC program VISLIMIT.BAS by Bradley E. Schaefer, Sky and Telescope, May 1998, p.57, in turn based on Schaefer Sky&Tel 78, 522 (1989).

Definition at line 802 of file visibility.f90.

Referenced by limmag_full().

◆ limmag_full()

real(double) function thesky_visibility::limmag_full	(	integer, intent(in)	year,
		integer, intent(in)	month,
		real(double), intent(in)	obselev,
		real(double), intent(in)	obslat,
		real(double), intent(in)	sunalt,
		real(double), intent(in)	sunelon,
		real(double), intent(in)	moonphase,
		real(double), intent(in)	moonalt,
		real(double), intent(in)	moonelon,
		real(double), intent(in)	objalt,
		real(double), intent(in), optional	humid,
		real(double), intent(in), optional	airtemp,
		real(double), intent(in), optional	snrat,
		integer, intent(in), optional	verbosity )

Calculate limiting magnitude based on Sun and Moon positions and phase, and on the altitude of the observed object.

Parameters

year	Year of observation (for solar cycle)
month	Month of observation (for approximate Sun RA)
obsElev	Elevation of the observer (m)
obsLat	Latitude of the observer (rad)
sunAlt	Altitude of the Sun (rad)
sunElon	Elongation object-Sun (rad)
moonPhase	Phase of the Moon (fraction)
moonAlt	Altitude of the Moon (rad)
moonElon	Elongation object-Moon (rad)
objAlt	Altitude of the observed object (rad)
humid	Relative humidity (%; optional, default: 70)
airTemp	Air temperature (degrees Celsius; optional, default: 10)
snrat	Snellen ratio for vision (optional, default: 1)
verbosity	Verbosity (optional, default: 0=quiet)

Return values

limmag_full Limiting magnitude - return >= 99 if the object is below the horizon

See also: BASIC program VISLIMIT.BAS by Bradley E. Schaefer, Sky and Telescope, May 1998, p.57, in turn based on Schaefer Sky&Tel 78, 522 (1989).

See also: Knoll, Tousey and Hulburt, J.Opt.Soc.Am. 36, 480 (1946); Hecht J.Opt.Soc.Am. 37, 59 (1947), Eq.3; Schaefer PASP 102, 212 (1990), Eq.2

Definition at line 717 of file visibility.f90.

References limmag_extinction(), limmag_full(), and limmag_skybrightness().

Referenced by limmag_full(), limmag_jd(), and limmag_sun_airmass().

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◆ limmag_jd()

real(double) function thesky_visibility::limmag_jd	(	real(double), intent(in), value	jd,
		real(double), intent(in), value	objra,
		real(double), intent(in), value	objdec,
		real(double), intent(in), value	objalt,
		real(double), intent(in), optional	lat,
		real(double), intent(in), optional	height )

Calculate limiting magnitude based on JD and object altitude, wrapper for limmag_full()

Parameters

jd	Julian day
objRA	Right ascension of the observed object (rad)
objDec	Declination of the observed object (rad)
objAlt	Altitude of the observed object (rad)
lat	Latitude of the observer (optional; rad)
height	Height/altitude of the observer above sea level (optional; metres)

Return values

limmag_jd Limiting magnitude

Note: Using observer's location from module TheSky_local; overruled by optional dummy variables lat and height

Definition at line 985 of file visibility.f90.

References thesky_local::day, thesky_local::height, thesky_local::lat0, limmag_full(), limmag_jd(), thesky_local::month, thesky_planetdata::nplanpos, thesky_planets::planet_position_la(), thesky_planetdata::planpos, and thesky_local::year.

Referenced by limmag_jd(), limmag_jd_pl(), limmag_zenith_jd(), and pl_xsmag().

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◆ limmag_jd_pl()

real(double) function thesky_visibility::limmag_jd_pl	(	real(double), intent(in)	jd,
		integer, intent(in)	pl )

Calculate limiting magnitude based on JD and planet ID, wrapper for limmag_jd()

Parameters

jd	Julian day
pl	Planet ID

Return values

limmag_jd_pl Limiting magnitude

Note: Using observer's location from module TheSky_local

Definition at line 1073 of file visibility.f90.

References limmag_jd(), limmag_jd_pl(), thesky_planetdata::nplanpos, thesky_planets::planet_position_la(), and thesky_planetdata::planpos.

Referenced by limmag_jd_pl().

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◆ limmag_skybrightness()

subroutine thesky_visibility::limmag_skybrightness	(	integer, intent(in)	year,
		real(double), intent(in), value	sunalt,
		real(double), intent(in), value	sunelon,
		real(double), intent(in), value	moonphase,
		real(double), intent(in), value	moonalt,
		real(double), intent(in), value	moonelon,
		real(double), intent(in), value	objalt,
		integer, intent(in)	band1,
		integer, intent(in)	band2,
		real(double), dimension(5), intent(in)	extcoef,
		real(double), dimension(5), intent(out)	skybr )

Calculate sky brightness based on Sun altitude and Moon phase.

Parameters

year	Year CE (for the solar cycle)
objAlt	Altitude of the observed object (rad)
moonAlt	Moon altitude (rad)
sunAlt	Sun altitude (rad)
moonPhase	Moon illuminated fraction (0-1)
moonElon	Moon elongation from observed object (rad)
sunElon	Sun elongation from observed object (rad)
band1	First of UBVRI bands to compute (1-5); compute band1-band2
band2	Last of UBVRI bands to compute (1-5); compute band1-band2
extCoef	Extinction for UBVRI
skyBr	Sky brightness for UBVRI in nanoLambert (output)

See also: BASIC program VISLIMIT.BAS by Bradley E. Schaefer, Sky and Telescope, May 1998, p.57, in turn based on Schaefer Sky&Tel 78, 522 (1989).

Definition at line 873 of file visibility.f90.

References thesky_moon::moonmagn().

Referenced by limmag_full().

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◆ limmag_sun()

real(double) function thesky_visibility::limmag_sun ( real(double), intent(in) sunalt )

Calculate limiting magnitude, based on the altitude of the Sun. Simplified version of limmag_full()

Parameters

sunAlt Altitude of the Sun (rad)

Return values

limmag_sun Limiting magnitude

Note

Mag depends only on sunAlt in rad
assume object in zenith, no moon (am=180), humidity 50%, T=10degC, lat=45deg, sn=1

See also: http://www.go.ednet.ns.ca/~larry/astro/vislimit.html, a JavaScript version of a BASIC program by Bradley E. Schaefer, Sky and Telescope, May 1998, p.57

Definition at line 1167 of file visibility.f90.

References limmag_sun().

Referenced by limmag_sun(), and pl_xsmag_la().

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◆ limmag_sun_airmass()

real(double) function thesky_visibility::limmag_sun_airmass	(	integer, intent(in)	month,
		real(double), intent(in), value	sunalt,
		real(double), intent(in), value	sunaz,
		real(double), intent(in), value	objalt,
		real(double), intent(in), value	objaz,
		real(double), intent(in), optional	lat,
		real(double), intent(in), optional	height )

Calculate limiting magnitude based on Sun altitude and object altitude (airmass). Assumes New Moon.

Parameters

month	Month of the year
sunAlt	Altitude of the Sun (rad)
sunAz	Azimuth of the Sun (rad)
objAlt	Altitude of the observed object (rad)
objAz	Azimuth of the observed object (rad)
lat	Latitude of the observer (optional; rad)
height	Height/altitude of the observer above sea level (optional; metres)

Return values

limmag_sun_airmass Limiting magnitude

Note: Using observer's location from module TheSky_local; overruled by optional dummy variables lat and height

Definition at line 1115 of file visibility.f90.

References thesky_local::height, thesky_local::lat0, limmag_full(), limmag_sun_airmass(), thesky_local::month, and thesky_local::year.

Referenced by limmag_sun_airmass().

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◆ limmag_zenith_jd()

real(double) function thesky_visibility::limmag_zenith_jd	(	real(double), intent(in)	jd,
		real(double), intent(in)	lat,
		real(double), intent(in)	lon,
		real(double), intent(in)	height )

Calculate limiting magnitude for the local zenith, based on JD and observer's location.

Parameters

jd	Julian day
lat	Latitude of the observer (rad)
lon	Longitude of the observer (rad)
height	Height/altitude of the observer above sea level (metres)

Return values

limmag_zenith_jd Limiting magnitude

Definition at line 1040 of file visibility.f90.

References thesky_datetime::calc_gmst(), thesky_coordinates::horiz2eq(), limmag_jd(), and limmag_zenith_jd().

Referenced by limmag_zenith_jd().

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◆ pl_xsmag()

real(double) function thesky_visibility::pl_xsmag	(	real(double), intent(in)	jd,
		integer, intent(in)	pl )

Compute the excess magnitude for planet pl at JD, considering Sun, Moon and airmass.

Parameters

jd	Julian day for moment of interest
pl	Planet ID (0-Moon, 1-Mer, 8-Nep, >10-comet

Return values

pl_xsmag The excess magnitude

Note

The excess magnitude is defined as the magnitude of an object MINUS the limiting magnitude
- xsmag < 0 - object is visible (in theory!) with the naked eye
The magnitude is corrected for extinction due to airmass, but for sea level
The limiting magnitude here solely depends on the Sun's altitude, simplified expression (especially, no Moon!)
This routine should be used as an indication only - no hard facts...

Definition at line 1215 of file visibility.f90.

References limmag_jd(), pl_xsmag(), thesky_planets::planet_position_la(), and thesky_planetdata::planpos.

Referenced by pl_xsmag(), and pl_xsmag_pl().

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◆ pl_xsmag_la()

real(double) function thesky_visibility::pl_xsmag_la	(	real(double), intent(in)	jd,
		integer, intent(in)	pl )

Compute the excess magnitude for planet pl at JD, considering airmass and Sun alt - low-accuracy version of pl_xsmag()

Parameters

jd	Julian day for moment of interest
pl	Planet ID (0-Moon, 1-Mer, 8-Nep, >10-comet

Return values

pl_xsmag_la The excess magnitude

Note

The excess magnitude is defined as the magnitude of an object MINUS the limiting magnitude
- xsmag < 0 - object is visible (in theory!) with the naked eye
The magnitude is corrected for extinction due to airmass, but for sea level
The limiting magnitude here solely depends on the Sun's altitude, simplified expression (especially, no Moon!)

Definition at line 1276 of file visibility.f90.

References airmass(), extinction_magpam(), limmag_sun(), pl_xsmag_la(), thesky_planets::planet_position_la(), and thesky_planetdata::planpos.

Referenced by pl_xsmag_la(), and pl_xsmag_la_pl().

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◆ pl_xsmag_la_pl()

real(double) function thesky_visibility::pl_xsmag_la_pl ( real(double), intent(in) jd )

Compute the excess magnitude at JD, wrapper for pl_xsmag_la() for solvers. The planet ID pl0 is passed through module planetdata.

Parameters

jd	Julian day for moment of interest

Return values

pl_xsmag_la_pl The excess magnitude

Definition at line 1309 of file visibility.f90.

References thesky_planetdata::pl0, pl_xsmag_la(), and pl_xsmag_la_pl().

Referenced by pl_xsmag_la_pl().

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◆ pl_xsmag_pl()

real(double) function thesky_visibility::pl_xsmag_pl ( real(double), intent(in) jd )

Compute the excess magnitude at JD, wrapper for pl_xsmag() for solvers. The planet ID pl0 is passed through module planetdata.

Parameters

jd	Julian day for moment of interest

Return values

pl_xsmag_pl The excess magnitude

Definition at line 1248 of file visibility.f90.

References thesky_planetdata::pl0, pl_xsmag(), and pl_xsmag_pl().

Referenced by best_planet_xsmag(), and pl_xsmag_pl().

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◆ planet_visibility_tonight()

subroutine thesky_visibility::planet_visibility_tonight	(	real(double), intent(in)	jd,
		integer, intent(in)	pl,
		real(double), intent(in)	sunalt,
		real(double), intent(in)	plalt,
		integer, intent(in)	comp,
		real(double), dimension(2), intent(out)	plvis,
		real(double), dimension(2), intent(out), optional	plazs,
		real(double), dimension(5), intent(out), optional	rts,
		real(double), dimension(5), intent(out), optional	tts,
		real(double), dimension(5), intent(out), optional	sts,
		real(double), dimension(5), intent(out), optional	ras,
		real(double), dimension(5), intent(out), optional	tas,
		real(double), dimension(5), intent(out), optional	sas,
		logical, intent(in), optional	rscwarn )

Compute when a given planet is visible in a given night.

Parameters

jd	Julian day for calculation
pl	Planet ID (1-2, 4-8 for Mer-Ven, Mar-Nep)
sunAlt	Sun altitude below which planet is visible (deg; e.g. -6.d0)
plalt	Planet altitude above which planet is visible (deg; e.g. 5.d0)
comp	Compute: 1-compute twilight/planet at plalt events only, 2-include actual rise/set times 11, 12 = 1, 2 + compute only for today, not tomorrow
plvis	Planet visibility times (hours): 1-begin, 2-end; plvis(1)*plvis(2) = 0 when invisible (output)
plazs	Planet visibility azimuths (rad): 1-begin of visibility, 2-end of visibility (output)
rts	"Rise times": 1-twilight (Sun at sunAlt), 2-Sun rise/set, 4-planet at plalt, 5-planet rise/set (output)
tts	Transit times: 1-2, of Sun, 4-5 of planet (output)
sts	"Set times": 1-twilight (Sun at sunAlt), 2-Sun rise/set, 4-planet at plalt, 5-planet rise/set (output)
ras	Rise azimuths: 1-2, of Sun, 4-5 of planet (output)
tas	Transit altitudes: 1-2, of Sun, 4-5 of planet (output)
sas	Set azimuths: 1-2, of Sun, 4-5 of planet (output)
rsCWarn	Print convergence warnings in riset() (optional; default = true)

Definition at line 215 of file visibility.f90.

References thesky_riset::riset().

Referenced by best_planet_xsmag().

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◆ skybrightness_cdm2_from_mlim()

elemental real(double) function thesky_visibility::skybrightness_cdm2_from_mlim ( real(double), intent(in) mlim )

Convert limiting visual magnitude to sky brightness in candela per square meter.

Parameters

mlim	Naked-eye visual limiting magnitude (V)

Return values

Sky	brightness in cd/m^2

Note: Inverse of skybrightness_mlim_from_cdm2()

Definition at line 1451 of file visibility.f90.

References skybrightness_cdm2_from_mlim(), and skybrightness_cdm2_from_nl().

Referenced by skybrightness_cdm2_from_mlim().

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◆ skybrightness_cdm2_from_nl()

elemental real(double) function thesky_visibility::skybrightness_cdm2_from_nl ( real(double), intent(in) nl )

Convert sky brightness in nanolambert to candela per square meter.

Parameters

nL	Sky brightness in nanolambert (nL)

Return values

Sky	brightness in candela per square meter (cd/m^2)

Definition at line 1475 of file visibility.f90.

References skybrightness_cdm2_from_nl().

Referenced by skybrightness_cdm2_from_mlim(), and skybrightness_cdm2_from_nl().

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◆ skybrightness_mas2_from_mlim()

elemental real(double) function thesky_visibility::skybrightness_mas2_from_mlim ( real(double), intent(in) mlim )

Convert naked-eye visual limiting magnitude (V) to sky surface brightness in (B) magnitudes per square arcsecond.

Parameters

Mlim	Naked-eye visual limiting magnitude (V)

Return values

skybrightness_mas2_from_mlim Sky surface brightness in (B) magnitudes per square arcsecond

See also: http://adsabs.harvard.edu/abs/1990PASP..102..212S

Note: Sky surface brightness is sometimes referred to as sqm (which is in fact a device to measure it)

Definition at line 1377 of file visibility.f90.

References skybrightness_mas2_from_mlim().

Referenced by skybrightness_mas2_from_mlim().

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◆ skybrightness_mlim_from_cdm2()

elemental real(double) function thesky_visibility::skybrightness_mlim_from_cdm2 ( real(double), intent(in) cdm2 )

Convert sky brightness in candela per square meter to naked-eye visual limiting magnitude (V)

Parameters

cdm2	Sky brightness in cd/m^2

Return values

Naked-eye visual limiting magnitude (V)

Note

Adapted from Weaver (1947) and Garsteng (1986):

shift to match data by Weaver (1947): 7.930 -> 7.706; 4.305 -> 4.115;
use candela per square meter instead of nanolambert.

Definition at line 1426 of file visibility.f90.

References skybrightness_mlim_from_cdm2(), and skybrightness_nl_from_cdm2().

Referenced by skybrightness_mlim_from_cdm2().

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◆ skybrightness_mlim_from_mas2()

elemental real(double) function thesky_visibility::skybrightness_mlim_from_mas2 ( real(double), intent(in) skybright )

Convert sky surface brightness in (B) magnitudes per square arcsecond to naked-eye visual limiting magnitude (V)

Parameters

skyBright Sky surface brightness in (B) magnitudes per square arcsecond

Return values

skybrightness_mlim_from_mas2 Naked-eye visual limiting magnitude (V)

See also: http://adsabs.harvard.edu/abs/1990PASP..102..212S

Note: Sky surface brightness is sometimes referred to as sqm (which is in fact a device to measure it)

Definition at line 1403 of file visibility.f90.

References skybrightness_mlim_from_mas2().

Referenced by skybrightness_mlim_from_mas2().

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◆ skybrightness_nl_from_cdm2()

elemental real(double) function thesky_visibility::skybrightness_nl_from_cdm2 ( real(double), intent(in) cdm2 )

Convert sky brightness in candela per square meter to nanolambert.

Parameters

cdm2	Sky brightness in candela per square meter (cd/m^2)

Return values

Sky	brightness in nanolambert (nL)

Definition at line 1494 of file visibility.f90.

References skybrightness_nl_from_cdm2().

Referenced by skybrightness_mlim_from_cdm2(), and skybrightness_nl_from_cdm2().

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◆ transitalt()

real(double) function thesky_visibility::transitalt	(	real(double), intent(in)	lat,
		real(double), intent(in)	dec )

Compute the transit altitude of an object with given declination for an observer with a given geographic latitude.

Parameters

lat	Geographic latitude of the observer (-pi/2 - pi/2; rad)
dec	Declination of the object (-pi/2 - pi/2; rad)

Return values

transitalt Transit altitude (rad)

Definition at line 441 of file visibility.f90.

References transitalt().

Referenced by comet_invisible(), and transitalt().

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Functions/Subroutines

Detailed Description

Function/Subroutine Documentation

◆ airmass()

◆ airmass_la()

◆ aperture()

◆ best_obs_date_ra()

◆ best_planet_visibility()

◆ best_planet_xsmag()

◆ comet_invisible()

◆ extinction_fac()

◆ extinction_mag()

◆ extinction_magpam()

◆ get_dra_obj()

◆ limmag_extinction()

◆ limmag_full()

◆ limmag_jd()

◆ limmag_jd_pl()

◆ limmag_skybrightness()

◆ limmag_sun()

◆ limmag_sun_airmass()

◆ limmag_zenith_jd()

◆ pl_xsmag()

◆ pl_xsmag_la()

◆ pl_xsmag_la_pl()

◆ pl_xsmag_pl()

◆ planet_visibility_tonight()

◆ skybrightness_cdm2_from_mlim()

◆ skybrightness_cdm2_from_nl()

◆ skybrightness_mas2_from_mlim()

◆ skybrightness_mlim_from_cdm2()

◆ skybrightness_mlim_from_mas2()

◆ skybrightness_nl_from_cdm2()

◆ transitalt()