Source elevation

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Description

Calculates source elevation and azimuth in degrees given declination, hour angle, and observatory latitude.

Usage

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elev(dec.sou = "33d 09m 35.0s", ha = 0, lat.obs = "38d 25m 59.2s")

azimuth(dec.sou = "33d 09m 35.0s", ha = 0, lat.obs = "38d 25m 59.2s")

Arguments

dec.sou

Source declination (string)

ha

Hour angle (decimal hours)

lat.obs

Observatory latitude (string)

Details

Enter latitude as s text string with fields separated by characters d, h, m, s, a colon, or a comma, e.g. '38d25m59.2s' or '38, 25, 59.2' or '38:25:59.2' or '38:25.987' for the Green Bank Telescope. Spaces are removed in input conversion. Decimal values for degrees or minutes are allowed. Trailing missing values are taken as zero.

Value

Source elevation or azimuth (E from N) in degrees.

Note

Geometrical calculation only, no corrections for refraction, aberration, precession, etc.

Author(s)

Andrew Harris

References

"Astrophysical Formulae," K.R. Lang, Springer c. 1986, 5-45

See Also

dms2rad, hms2rad for input formats, ut2ha to convert UT to hour angle.

Examples

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# Maximum elevation at Green Bank
elev(dms2rad('-28, 20'))

# Maximum elevation at Mauna Kea
elev(dms2rad('-28, 20'), 0, '19:49')

# Plot elevation and azimugh vs. hour angle
ha <- seq(0, 24, 0.25)
el <- elev('30d 33m 22s', ha)
plot(ha, el, t='l', col=4)
az <- azimuth('30d 33m 22s', ha)
plot(ha, az, t='l', col=4)

# Plot elevation and azimuth vs. UT (using many defaults)
h.ut <-  seq(0, 24, 0.25)
el <- elev(dec.sou='30d 33m 22s', ha=ut2ha(hr=h.ut))
plot(h.ut, el, t='l', col=4)
az <- azimuth(dec.sou='30d 33m 22s', ha=ut2ha(hr=h.ut))
plot(h.ut, az, t='l', col=4)