Originally from ticket #12469.
I would like to observe moon phases as seen from any location in the first century AD, in order to help verify the Biblical lunar calendar.
a. What program version would do this with best results?
b. How would you quantify the time accuracy of your programs (e.g., ±8hrs/millenium)?
c. What time units are used in the program?
d. How are leap years and calendar discrepancies handled?
Hi Randy,
Forgive me for the slow reply to your query.
a. What program version would do this with best results?
All the the program allow you to observe the phases of the Moon during Biblical times.
b. How would you quantify the time accuracy of your programs (e.g., ±8hrs/millenium)?
Accuracy in astronomical calculations is a tricky thing. There are a lot of competing factors and it's often difficult to know how right or wrong you are, because you can't go back in time to test your calculations. We've done our best to be accurate in our calculations, but things in the heavens aren't as clockwork as you might believe.
One major contributor to the accuracy (or lack thereof) of any historical astronomical calculation is the value of "Delta - T" you use. Delta - T is a complicated thing, but to summarize, it's the x-factor that takes into account all of the small things that can speed up and slow down Earth's rotation, and hence change the "time".
The Wikipedia entry is pretty good:
http://en.wikipedia.org/wiki/ΔT
So, the best thing we can do is to try to match up what is displayed in Starry Night with actual recoded astronomical events, like eclipses, which seem pretty good.
Starry Night has been used for "Archeoastronomy" before and has been found by many people to be accurate, matching up with e.g. precisely measured eclipses and other events far into the past. That being said, nothing can be %100 accurate, computers are only as good as the models they use and we're doing our position calculations in "real time" in order to present a smooth, "movie like" quality. If you want extremely precise calculations for a given planet, I'd encourage you to use Starry Night as a primary source, then use NASAs JPL Planetary Ephemerides calculator to get precise positions (and also check USNO). It's more complicated, requiring a better understanding of Astronomy, but you'll get more precise (and perhaps more accurate) results.
See the full answer here:
c. What time units are used in the program?
Attached is a screenshot showing time units. Universal Time is also available in Pro & Pro Plus.
d. How are leap years and calendar discrepancies handled?
Starry Night uses established code calculations that handle these queries. The code is not available for general viewing. (If you wish to expand upon this question in such a way that it can be answered without revealing the code please feel free.)
Does all this help?
Again, I apologize for the slow reply.
