Issues with accuracy

Asked by Jess Allen Glowacki on 2017-06-11

I'm no expert, but am an Architect and have been wanting to use your software and all the great information gathered to create a planetarium which can teach about the stars and their meaning to different cultures around the world and also incorporate it into design software that I use to create VR experiences and hopefully in the built environment. If anyone is interested in helping me out with these endeavors please contact me as well.

I have found a few issues that I just want some clarification on and wondering if it is just a software issue or what.

1. When looking to the sunrise in Giza from 2005 to 2014 the time of sunrise skips about an hour from the time before and after. Not sure is we had some shift or if this is just a fluke in the programming. Again I am no expert. I noticed there is a 4 year flux in the movement that is normal in the cycle, but the jump is what is not making sense to me.

2. When looking a Sirius on the horizon line setting late in the year it jumps off the horizon and changes position in the sky when I look at it from 2000 years ago to now. Again, this seems to be inaccurate and should be more consistent.

If anyone could please help me understand why this is happening would be much appreciated.

Thank you,

Jess Allen Glowacki
ECOPHI Architecture
231 412 0033
<email address hidden>

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Alexander Wolf (alexwolf) said : #1

Sorry, but without info about version of Stellarium we can guessing about source of "mistakes".

1. Seems like enabling/disabling DST or "problem" with leap year.

2. Coordinates of celestial objects are changed in time from the axial precession and delta T ( andΔT)

gzotti (georg-zotti) said : #2

Since about version 0.11, I have worked to make Stellarium more accurate and usable for this very purpose: historical skyscape simulation including 3D models and allowing virtual walkthroughs.

(1) jump "by 1 hour" looks like Alex is right. Use the latest version and set timezone properly. Use Local Mean Time for antiquity.

(2) is intentional and reflects precessional shift and proper motion of Sirius. This is why only virtual archaeoastronomy can provide pictures of stars rising in their correct places in antiquity. I don't understand what you mean by "jump off the horizon". If "late in the year" means anything like "late december days", forget those date names in the Julian calendar used by the program, they may be two weeks off from the dates we usually know when you simulate Old Kingdom times. Observe solar longitude.

We would very much welcome contributions of royalty free good and accurate architecture/landscape models of relevance for demonstration in Cultural Astronomy, e.g. temples, churches with solar orientation or light-and-shadow effects like window light moving over paintings on particular dates, ... The Guide contains guidelines how to prepare a georeferenced OBJ model with accurate coordinates.

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