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Nicol�s de Hister wrote-

lately I found Stellarium (http://www.stellarium.org/) and discussed 
its
accuracy on this list [NavList 1793-1802]. As Frank Reed found out
[NavList 1802] it does not yet incorporate proper motion yet.

===========================

response from George.

Yes, I had seen Nicol�s' previous posting about Stellarium with some 
interest, but the lack of proper-motion rules it out. Many of the 
stars I would wish to follow have enough proper motion to make a very 
significant shift in position over 3 centuries, enough to move them 
well outside my precision limit of 0.1 arc minutes.

So I remain interested in discovering details of an alternative that 
may meet my needs. I'm quite prepared to pay hard cash for it (within 
limits...) but of course a free version is preferred, and Stan, at 
SLK1000@aol.com  , has suggested some names, but without details.

And helpfully, Guy Schwartz has added-

>I have Starry Night pro. It might do what you need. I'm willing to 
>try.

If Guy could discover whether it meets my needs, that would indeed be 
welcome.

==================

I'm not asking, however, for specific sky-positions, at certain dates 
and times, to be read out for me. I need a program to provide a 
display that I can play with, because it's the geometric alignments 
between various bodies that are important.

In case it helps, here once again is what I am seeking-

=============================

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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