HET General Observability Calculator

This program allows a PI to determine generally when his or her targets can be observed. It will give the first date that the specified target has its East trajectory midpoint at 18 degree morning twilight, and the last date when its West trajectory midpoint is at 18 degree evening twilight.

More flexible observability criteria, such as the availability of a given threshold of sky darkness, will be handled by an Observability Calendar, in preparation.

In practice the observing Resident Astronomer has slightly more flexibility than implied here, for about half of the sky, in the azimuth quadrants bracketing the North and the South point. To the extent that the sky transits the HET accessiblity locus at a shallow angle, there is often scope to choose an HET azimuth not corresponding to the target's 55 degree elevation transit. This can enable freer choices of acquisition times with negligible or entirely acceptable loss of net pupil compared with the standard track geometry. As there are many parameters involved with this mode, it is not considered in the baseline calculation here. Incidentally a further benefit of this capability is to alleviate some scheduling conflicts when high priority tracks overlap in sidereal time.

Enter the RA and Dec below and hit the submit button. Please use either h:m:s or h m s for RA format below. Please use either d:m:s or d m s for DEC format below.