The programme observe is designed to allow you to get a quick overview of the observability of a star through the year from the geographical location selected. You will be prompted for the RA and Dec of the star, the telescope (you can also specify arbitrary locations), and the year. On the selected GKS graphics device a plot will be drawn that tells you, for all dates of the year, the star rising and setting times and the times that it is 30 above the horizon, the times of astronomical twilight, the phase and rising and setting times of the Moon as well as its distance from the star in question.
The algorithms used in calculating these times, positions and phases come from the book ‘Practical Astronomy with your calculator’ by P. Duffett-Smith (3 ed. CUP 1988), and are used with permission. These algorithms are not designed for high-precision calculations, a fact which is to some extent conveyed by the programme output. Nevertheless, we have verified that the routines are good for their purpose.
As mentioned above, all standard Starlink graphics devices are supported. However, the graphical output created by observe is sufficiently complicated and the device drivers have sufficiently different effects that plotting to a laser printer is almost certainly the best option. We recommend that the GKS landscape postscript device ps_l is chosen. The following command will then print the output file (% is the shell prompt):
where star_post is the name of the postscript printer. (Subsequent plots to this device produce
filenames gks74.ps.1, etc). You can also look at this output file on an X-terminal using ghostview in
landscape mode.
The programme observe was originally created by Manfred Gottwald, then of the EXOSAT Observatory. We have increased the quantity of information displayed and increased the list of standard observatories, and now take responsibility for this software.