Re: astronomy/moon accuracy in BCE years, customizing formulas
- From: "Mike Dworetsky" <platinum198@xxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 13 Feb 2008 08:38:14 -0000
"mtnview" <astro.div@xxxxxxxxx> wrote in message news:5b02037a-b602-497b-bb08-d5b82a37d59e@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Greetings -
I hope this is the right place. I'm looking for experts on
astronomical calculations to answer some questions as I develop some
software. I know how to develop software in general, but I only know a
little about astrophysics or astronomy theories. My focus for now
would be on the moon, the planets later.
I'm new to this usenet group thing, so I don't know if it is
appropriate to ask here, but I'm willing to pay someone for ongoing
questions and consultation and/or programming if anyone is interested.
I only bring this up because I don't know where else to look
(freelance type sites and yahoo answers, etc, aren't expert enough
from what I've seen; but if any of you are on those sites, let me
know). If you're willing to share your expertise, I'll gratefully
learn from it, but I may need help beyond what can be given here.
Here are my primary questions:
Is it possible to accurately calculate moon data (phase, age, azimuth,
altitude, rise/set, perigeee, apogee, zenith angle, eclipses, and so
forth) back to say, 5000BC?
Keep in mind "accurate", for my purposes, could be -- as an example --
within 1 minute (by the clock) for the moonrise. Actually, for the BCE
years, 5-10+ minutes would be reasonable. In the present or past/
future centuries I'd want less than 60 seconds for the moon position
or better. Phase/age in BCE years could be off by hours, as long as it
was generally the correct phase.
What type of accuracy is required to properly calculate the times of
eclipses (lunar, solar) in the present or near future (~20 yrs)?
How difficult is it to get accurate calculations in the arctic
regions?
Most formulas I've used allow input of a date, and output object data
for that date. Is it easy to calculate the opposite? ie, at what date
will the moon appear on the horizon at azimuth x?
Do formulas exist for outputting the moon or planet position every x
minutes (ie, every 30 minutes, or every 2 seconds) instead of
recalculating the entire formula at every iteration? (I think this
would help speed up animations)
Finally, I'm toying with the idea of 3-D models of the solar system
where each object can be positioned accurately with respect to each
other at any given date and time. Is this very difficult, or do models
already exist for this that can be plugged into animation-enabled
development software like Flash?
Thanks for your help.
There are many available "planetarium" programs that do this. The main obstacle to accurate calculations going back to 5000BCE is that we don't have precise information on the varying rotational rate of the Earth because the various tidal and moment of inertia effects are not constant. What we do have is interpolation fits based on ancient manuscripts, and in general this material only goes back about 1500-2000 years (and few of those).
The net result is that, as viewed from a particular location, we can't say with any accuracy that a solar eclipse, for example, would have been visible from Athens in 3000BCE. We can calculate the eclipse itself reasonably accurately, but not where it was seen on Earth (in longitude).
--
Mike Dworetsky
(Remove pants sp*mbl*ck to reply)
.
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