User guide to program with celme Python classes¶

This section show how to use celme in a Python code.

1. Context¶

Celestial mechanics allow to compute celestial bodies positions and manage dates, durations, angles, coordinates.

2. Python classes provided by celme¶

Brief descrition of the celme classes:

Angle: Convert angles in complex formats.

Coords: Convert angles in complex formats.

Home: Define a mount location on the Earth surface.

Horizon: Define horizon line to set the limits of telescope pointings.

Atmosphere: Define atmospheric conditions to set the conditions to compute refraction effects.

Site: Define an observation site by merging Home, Horizon, Atmosphere.

Date: Convert dates in complex formats.

Duration: Convert durations in complex formats.

Mechanics: Low level methods for celestial mechanics

Targets: High level methods for celestial mechanics

3. Using the Python module celme for angles¶

3.1. Simple example to convert angles¶

import celme
a = celme.Angle("2h3m27s")
print("angle deg =", a.deg())

angle deg = 30.862499999999994

3.2. Operation with angles¶

We want to compute sum of the angles 2h3m27s and -0d28m12.4s. Display the results in sexagesimal format expressed in degrees:

import celme
a = celme.Angle("2h3m27s")
b = celme.Angle("-0d28m12.4s")
c = a + b
print("{}".format(c.sexagesimal("d")))

‘30d23m32.60s’

4. Using the Python module celme for dates¶

Celme module is located in the folder pyros/src/utils Examples: pyros/src/utils/report/dates.py help(Date)

4.1. Simple example to convert dates¶

import celme
a = celme.Date("now")
print("Date ISO =", a.iso())
Date ISO = 2018-10-11T22:45:44.958
print("Date Julian Day =", a.jd())

Date Julian Day = 2458403.448437011

4.2. Operation with dates¶

We want to compute date corresponding to add 2 days and 28 minutes to the 2018-10-11T22:45:44.958. Display the results in ISO format:

import celme
a = celme.Date("2018-10-11T22:45:44.958")
b = celme.Duration("2d28m")
c = a + b
print("Date ISO =", c.iso())

Date ISO = 2018-10-13T23:13:44.958

5. Using the Python module celme for ephemeris¶

Celme module is located in the folder pyros/src/utils

Examples: pyros/src/utils/report/targets.py

help(Target)

5.1. Simple example to compute Sun coordinates¶

First we compute RA, DEC coordinates of the Sun:

import celme
date = celme.Date("now")
site = celme.Site("GPS 0 E 49 200")
skyobj= {'planet':'Sun'}
target = celme.Target()
target.define(skyobj)
output0s = ['ra','dec']
results = target.ephem(date,site,output0s)
ra = results['RA']
dec = results['DEC']

Second, we inject RA, DEC to compute its local coordinates:

skyobj= {'RA':ra , 'DEC':dec }
outputs = ['elev']
target.define(skyobj)
results = target.ephem(date,site,outputs)
elev = results['ELEV']

6. Angle formats¶

Input accepted formats:

-12.345 : Decimal degrees
-0.3421r : Decimal radians
6h3m2s : Sexagesimal HMS
3mh2s : Sexagesimal MS
2sh : Sexagesimal S
6d3m2s : Sexagesimal dms
3m2s : Sexagesimal ms
2s : Sexagesimal s (i.e. arcsec)
“6 3 2” : Sexagesimal dms
“6:3:2” : Sexagesimal dms
“6h3:2” : Sexagesimal HMS

Sexagesimal formating using uspzad convention rad is an angle in radian Sexagesimal format:

u (unit) = h,H,d,D (default=D). Capital mean module [0:360[, lower case means module [-180:180[

s (separator) = ” “,:,”” (default=”” means letters hms or dms)

p (plus/minus) = +,”” (default=”“)

z (zeros) = 0,”” (default=”“)

a (angle_limits) = “”,90, (+/-limit if unit D,H, default=”” means 360)

d (sec_digits) = “”,”.1”,”.2”,… (default=”“)

Style 1:

To Display a R.A.: “H0.2” => 23h07m42.49s

To Display a Decl.: “d+090.1” => +00d34m22.6s

To Display a H.A.: “h0.2” => -08h43m16.05s

Style 2:

To Display a R.A.: “H 0.2” => 23 07 42.49

To Display a Decl.: “d +090.1” => -00 34 22.6

To Display a H.A.: “h 0.2” => -08 43 16.05

Style 3:

To Display a R.A.: “H:0.2” => 23:07:42.49

To Display a Decl.: “d:+090.1” => -00:34:22.6

To Display a H.A.: “h:0.2” => -08:43:16.05

7. Date formats¶