Request: archaeo-astronomy features

Bug #518091 reported by ianto
8
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Stellarium
Fix Released
Wishlist
gzotti

Bug Description

Hello there

I use Stellarium for archaeo-astronomy, so I'm using ancient stone circles as a landscape and trying to find out positions of Sun-rises and sunsets etc. in relation to the standing stones within the landscape. Unfortunately, at Sunrise and sunset, the landscape goes dark! This makes it very difficult to see what is going on - great for photo-realism but not great for me. Also, when the atmosphere is turned on it's not easy to see the central disc of the Sun because of all the glare. Can we have toggles to take care of these problems? E.g. a thin circle could be drawn around the disc of the Sun to make it more obvious.

The new compass and angle plug-ins with 0.10.3 are great but I would like to see a feature for "landscape lines", that is, lines centred on the position of the observer that run along the ground to the horizon at a given Azimuth angle. The ability to plot several of these and also to be able to measure the angles (on the ground) between them would be a boon.

In addition to this it would be nice to be able to draw straight lines on the landscape between arbitary ground positions (i.e. not centred on the viewer)

The ability to save all these lines so that they can be loaded up at a later date would be important, obviously.

For archaeo-astronomy it is crucial that the landscape is oriented correctly so that East in the landscape matches with true East etc. However at the moment this either involves a lot of image manipulation or doing calculations to find a value for Rotatez. It would be a lot nicer if it were possible to re-position the landscape by dragging and dropping within Stellarium, which would update the value of Rotatez in the landscape.ini file, and then "locking" it in place once it is positioned correctly. This feature could also be used to get the horizon properly positioned.

Finally would it be possible to have an option for a translucent landscape toggle? This would be a boon because the landscape of today might be very different from the landscape of 4000 years ago. It would also make it easier to see when the Sun is about to rise etc.

That's all I can think of for now.

Ian

Changed in stellarium:
importance: Undecided → Wishlist
Revision history for this message
gzotti (georg-zotti) wrote :

Hi! I am using Stellarium for similar things.

Actually, at least the old_style landscape currently is buggy regarding the altitude position (decor_alt_angle and decor_angle_shift). I sent a partial fix (only landscape, no correction for fog so far) to Fabien, but he wants a cleanup in this landscape type, so it is not yet in 0.10.3, and you should stick to the newer landscape types.

Regarding horizon brightness at sunset, he accepted my simple brightening approach for 0.10.3.

For archaeo-astronomy, please be aware that some issues (deltaT and high-precision precession) are currently only in the "blueprints" wishlist.

Actually, for alignment studies, a plugin allowing a walkthrough in a 3D model would be a splendid addition.

I think Stellarium has high potential here!

Regards,
Georg

Revision history for this message
ianto (ianto09) wrote :

I can now create translucent landscapes by editing the png with GIMP - the effect is a bit strange with the atmosphere on but it looks normal with the atmosphere off. It would be neater as a toggle if that were possible. I still want to be able to see the landscape at the dead of night, so I want a toggle to prevent the landscape going dark, or some kind of "torch" feature.

Another useful feature for archaeo-astronomy would be the capability to annotate landscape features, e.g. "stone #1" "stone #2" and to be able to save and load this text later.

I think 3D is more advanced than I was thinking of. It would require the ability to model not just relative positions of stones but the whole landscape, no easy task. As Paul Deveraux once said stone circles etc. are "embedded in the landscape" it would be a mistake to abstract them from that, IMHO.

regards

Ian

Revision history for this message
Graham (tograhamr) wrote :

Would love if there was a function similar to 'CDC Horizon' to map exact horizon through telescope/finder, that would convert me 100% from Cartes Du Ciel to Stellarium!! :)

Great job with the Artificial Satilites!!!

Many thanks,

Graham

Revision history for this message
ianto (ianto09) wrote :

According to Stellarium, the Vernal Equinox in 2000BC occurred on April the 7th !!! The dates of the solstices etc. have also drifted. Archaeo-astronomers are interested in the Ancient World, the era when the pyramids, Stonehenge, Avebury and the other stone circles were built. It would be great, therefore if Stellarium, or a derrivative version, could handle the dates/times of the equinoxes, solstices etc. with greater accuracy for the period we are interested in.

Thankyou very much for reading this.

Ian

Revision history for this message
gzotti (georg-zotti) wrote :

Hi!

These date shifts are caused by using the Julian calendar for dates before 1582-10-15 in all mainstream astronomy programs I am aware of. It is not the equinoxes that are on wrong dates, it is that the days with the equinoxes etc. carry unexpected names. See the equinox date for 1580, for instance!

The only meaningful solution for archaeoastronomy in those remote times is to work with solar ecliptical longitudes, i.e. lambda=0 at spring equinox, lambda=90 at summer solstice etc. Even the Gregorian calendar is not free from date shifts, although they progress much slower.

For publications for an audience unaware of details in calendrical issues, you could work with a "conventional calendar" that has Spring equinox on March 21, and always say "... date would be ... in our current calendar." Maybe the IAU has a recommendation, but I have not seen it and have no better solution than this.

I (and apparently some other person, see blueprints, but the wish is not clearly enough expressed) would like to have ecliptical longitude displayed in the object data, apparently for this very reason.

A slightly more difficult solution could be a calendar plugin where you could select different calendar systems, including the abovementioned unknown "conventional calendar". Given the potential user base, I would prefer if development energy would concentrate on astronomical issues that matter much more here: precession, lunar rotation, ecliptic of date, ... (the simple solution of ssystem.ini is not enough or not correct for Earth/Moon.)

Also (ceterum censeo...), for visual astronomy (including, but not limited to archaeo-astronomy), extinction and refraction would be very important. (It's in the blueprints already, but not started.)

Kind regards,
Georg

Revision history for this message
ianto (ianto09) wrote :

Hi

Many thanks for the useful feedback on this, to start with.

One of the big problems I have is getting the horizon right. Where the Sun rises over the "natural" (as opposed to flat) horizon can be affected greatly by the relative vertical position of the landscape.png image. Even when it's okay for one zone it can be inaccurate in another. I spend a lot of time in GIMP shunting the main body of the landscape a few pixels up or a few pixels down. Any insights gratefully received.

It would be great to be able to "go to" a vernal/autumnal equinox sunrise for a particular year, or "go to" a midsummer/midwinter Sunrise in an automated way. Same for lunar standstills. Save having to guess what date it should be on!

Many thanks again for a truly great piece of software.

Ian

Revision history for this message
gzotti (georg-zotti) wrote :

Hi!

See my reply of 2010-02-07: The old_style horizon is buggy, the math for the altitudes is simply wrong, no matter how you shift it. Please use the newer types for now. If your pano itself is skewed, you must solve this with your pano stitcher.

Speaking of horizons, it's funny there are a few versions of "Stonehenge" out there, but most are not aligned correctly. What's the point then, dear pano makers?

Maybe the "Goto equinox" or "Goto [<next|previous>] sun at lambda=[0/45/90/135/180/225/270/315]-dropdown" can be solved with a script or simple plugin.

For the lunar standstills, it is far more difficult: You can compute theoretical limits when the lunar orbit is tilted most/least, but when the moon itself will be at (or better: closest to) these positions is another issue. Include lunar parallax for some more arcminutes of variance, .... See the chapters in Astronomical Algorithms on the lunar motions.

It may be great however to see a new time-lapse mode with the moon locked in a certain altitude, kept in center of screen, and shown from day to day or in weekly/monthly/... intervals in whichever phase it is, or even locked to a certain phase (i.e. the rise/set closest to the time of the respective phase). Maybe even only show "Full moon closest to [Winter|Sommer] solstice", going to the next year in each step. - You will be able to see the moon "dance" along the horizon, and you will see the difficulties most archaeologists have when hearing about lunar standstill alignments - those require decades of observations!

Anyway, imagine you could also plan exciting photographs of moonrise/-set with such a tool. So programmers out there, what about a "Moonrise catcher" plugin? Or even generalize it to catch any planet?

Best regards,
Georg

treaves (treaves)
Changed in stellarium:
status: New → Opinion
Revision history for this message
ianto (ianto09) wrote :

In addition to finding equinoxes and solstices, it would be useful to be able to find the cross-quarter days.

Has no-one taken up the gauntlet yet?

If are developing plug-ins etc. for this kind of thing, please let us know.

Ian

tags: added: archaeoastronomy
Revision history for this message
Alexander Wolf (alexwolf) wrote :

Please check version 0.13.66.0

Revision history for this message
ianto (ianto09) wrote : Re: [Bug 518091] Re: Request: archaeo-astronomy features

On 16/08/2015 18:41, Alexander Wolf wrote:
> Please check version 0.13.66.0
>

Many thanks!

Ian

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Revision history for this message
gzotti (georg-zotti) wrote :

Hehe, seeing this old bug report again is funny. Meanwhile we have accurate landscapes, 3D sceneries (sure, use a large patch of landscape around your stone circles!), CDC polygonal landscapes (mixable with photopano!), landscape feature labels, hi-quality precession, DeltaT, and ArchaeoLines.
Interactive (mouse-drag) rotation of landscapes seems not useful for me. It invites to rotate the landscape until it fits your expectation. Rather do an accurate pano and ensure accuracy in your pano stitcher.
There are still a few things on my personal wishlist, but there is always less time than needed...

Revision history for this message
gzotti (georg-zotti) wrote :

I regard this as fulfilled. Landscapes can be done CDC-style, high-accuracy, no problem. We will not have interactive fitting of panoramas, on purpose.

Changed in stellarium:
assignee: nobody → gzotti (georg-zotti)
milestone: none → 0.16.1
status: Opinion → Fix Committed
Changed in stellarium:
status: Fix Committed → Fix Released
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