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I'm enquiring about a suitable sky display program, to help with a
little research project into navigation history.

For that job, I need to display a picture of a small part of the
visible sky, plotted in altitude and azimuth, expandable up to (say) a
couple of degrees across the screen, with sky objects reasonably
precisely positioned for dates around 1700 AD, with errors no more
than 0.1 arc-minutes. I also need to know the coordinates of selected
objects in terms of (geocentric) ecliptic longitude and latitude, to
the same sort of precision, ideally with movable grid lines
corresponding to those coordinates. I need that display to show (from
a chosen geographic position) a precise view of the Moon, at its
correct diameter, and with its shadow-terminator rigorously calculated
according to the actual positions of Sun and Moon at that moment.

I have tried the program Skymap, which seems to fill the bill in every
respect but one. Although it provides alt/az, and RA/dec, it doesn't
display ecliptic lat/long. It provides a grid of ecliptic lat and
long, but only at 1-degree intervals, which is not good enough.

I know that I can calculate ecliptic coordinates from RA/dec, knowing
the obliquity of that date, but for this job it would be far more
convenient to have them displayed on screen.

I wonder if any NavList member has access to a sky-astronomy program
which they can recommend, as fitting those somewhat odd and demanding
requirements?

George.

contact George Huxtable at george@huxtable.u-net.com
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.


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