Utilities¶

tom_observations.utils.
get_sidereal_visibility
(target, start_time, end_time, interval, airmass_limit)¶ Uses astroplan to calculate the airmass for a sidereal target for each given interval between the start and end times.
The resulting data omits any airmass above the provided limit (or default, if one is not provided), as well as any airmass calculated during the day (defined as between astronomical twilights).
Important note: only works for sidereal targets! For nonsidereal visibility, see here: https://github.com/TOMToolkit/tom_nonsidereal_airmass
 Parameters
start_time (datetime) – start of the window for which to calculate the airmass
end_time (datetime) – end of the window for which to calculate the airmass
interval (int) – time interval, in minutes, at which to calculate airmass within the given window
airmass_limit (int) – maximum acceptable airmass for the resulting calculations
 Returns
A dictionary containing the airmass data for each site. The dict keys consist of the site name prepended with the observing facility. The values are the airmass data, structured as an array containing two arrays. The first array contains the set of datetimes used in the airmass calculations. The second array contains the corresponding set of airmasses calculated.
 Return type
dict

tom_observations.utils.
get_astroplan_sun_and_time
(start_time, end_time, interval)¶ Uses astroplan’s time_grid_from_range to generate an astropy Time object covering the time range.
Uses astropy’s get_sun to generate sun positions over that time range.
If time range is small and interval is coarse, approximates the sun at a fixed position from the middle of the time range to speed up calculations. Since the sun moves ~4 minutes a day, this approximation happens when the number of days covered by the time range * 4 is less than the interval (in minutes) / 2.
 Parameters
start_time (datetime) – start of the window for which to calculate the airmass
end_time (datetime) – end of the window for which to calculate the airmass
interval (int) – time interval, in minutes, at which to calculate airmass within the given window
 Returns
ra/dec positions of the sun over the time range, time range between start_time and end_time at interval
 Return type
astropy SkyCoord, astropy Time