|
```python
from astropy import units as u
from astropy.coordinates import SkyCoord,
EarthLocation, Longitude, Latitude,
CIRS
# Define ICRS coordinates
source = SkyCoord(
'16h 29m 24.45970s',
'−26d 25m 55.2094s',
d = u.AU / 5.89 * u.mas,
pmra = -12.11 * u.mas / u.yr,
pmdec = -23.30 * u.mas / u.yr,
rv = -3.4 * u.km / u.s)
# Observer location
loc = EarthLocation.from_geodetic(
Longitude(50.7374),
Latitude(7.0982),
height=60.0)
# Set time of observation
time = astropy.time.Time(
"2025-02-27T19:57:00.728+0200"
scale='tai')
# Observer frame & system
frame = CIRS(obstime=time, location=loc)
# apparent coordinates
apparent = source.transform_to(frame);
```
|
```c
#include
cat_entry star;
object source;
observer loc;
novas_timespec time;
novas_frame frame;
sky_pos apparent;
// Define ICRS coordinates
make_cat_entry("Antares", "ICRS", 1,
novas_hms_hours("16h 29m 24.45970s"),
novas_dms_degrees("−26d 25m 55.2094s"),
-12.11, -23.30, 5.89, -3.4, &star);
make_cat_object(&star, &source);
// Observer location
make_gps_observer(50.7374, 7.0982, 60.0,
&loc);
// Set time of observation
novas_set_str_time(NOVAS_TAI,
"2025-02-27T19:57:00.728+0200",
LEAP_SECONDS, DUT1, &time);
// Observer frame
novas_make_frame(NOVAS_FULL_ACCURACY,
&loc, &time, DX, DY, &frame);
// apparent coordinates in system
novas_sky_pos(&source, &frame, NOVAS_CIRS,
&apparent);
```
</td>
</tr>
</table>
Yes, __SuperNOVAS__ is a bit more verbose, but not painfully so. OK, it's cheating a little bit, but only to make a
point. If you look closer, you'll see that some details have been glazed over. For example, __astropy__ will
automatically fetch IERS data (leap seconds, and Earth-orientation parameters), whereas in __SuperNOVAS__ you will
have to set these explicitly (hence the placeholder `LEAP_SECONDS`, `DUT1`, `DX` and `DY` constants in the C snippet
above). And, of course, the above comparison ignores error checking also. In Python, you can simply surround the above
code in a `try` block, and then catch errors using `except`. In C, there is no catch-all solution like that. Instead,
you will have to check the return values for each line, and decide if you need to bail early, e.g.:
```c
if(make_cat_object(&star, &source) != 0) {
// oops, the above failed, bail if we must...
return -1;
}
```
Regardless of the slight omissions, the difference is not night and day. If you can handle __astropy__, chances are
you can handle __SuperNOVAS__ too. And the reward for dealing with slightly 'uglier' code, is orders of magnitude gain
in the speed of execution. It is a trade-off that worth considering, at the least.
-----------------------------------------------------------------------------
Copyright (C) 2025 Attila Kovács
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