Suggestion to help planet motion demos

[John Cotton]

There are times when a planet motion demonstration would be MUCH more effective if daily motion could be suppressed while time runs. Let everything else move - just with no daily sky motion. You would position the sky as desired, turn off daily motion, then run time so planet motion over time can be clearly shown.

A flag variant (like flag daily_motion on/off) could control it.

John Cotton

[Rob Spearman (rob-digitaliseducation)]

This is what the sidereal time keys and related features are for. Also see, for example, the annual motion script.

Rob

[John Cotton (jcotton)]

Thanks for the quick reply. I looked at the annual motion script. Forgive me for this, but that is the most awkward and clumsy way to do it I can imagine. In Digistar you simply suppress daily motion. Here's what it looks like in a D3 script. This is from my Christmas show.

21:47 scene date -5-04-17 08:00:00 dur 30 # Set Apr 17, 6 BC # Set up the sky.

22:22 eye daily off # Suppress daily motion
                scene date -4-01-31 sunset duration 50 # advance to Jan 1, 5 BC over 50 seconds
               Jupiter trail on # Jupiter leaves trail

That's all there is to it. The first date motion takes 30 seconds with daily motion, then the Jupiter sequence occurs over 50 seconds without daily motion. The first date setting occurs 21:47 into the show and the second at 22:22.

Hppe I'm not too much of a bother.

Jphn Cotton

[Rob Spearman (rob-digitaliseducation)]

Actually, I see the annual motion script was an old version, it should say:

date sidereal 1
...

If that still seems awkward, please explain a bit more on why.

Rob

[John Cotton (jcotton)]

You are right about the old script. It's the one I have with the Community version.

One question - is the date change from date sidereal 1 instantaneous or can the time it takes be specified?
The D3 script allows me to specify how long the change takes. In the example I sent the second date
change takes 50 seconds to run. Time runs smoothly during the change. The Nightshade docs don't
make that clear

Thanks

John Cotton

[Rob Spearman (rob-digitaliseducation)]

You can specify that with the wait between the sidereal date commands
but there is not something like a change duration on the date command.

Rob

[Lionel RUIZ (astro2kpremium)]

The thing is that the movement can be coarse as it's a step of time day after day.
And not as smooth as it can be if it is for example to watch the moon motion through time.

But there's a trick to fix the sky position instead of the horizon in nightshade by selecting a star (choose a zenithal star for example) and centering the view on it.
That way you'll get the sky still and with the command "timerate" you get planets movements smoothly.

Example selecting Vega:

select HP 91262
flag track_object on
flag atmosphere off
flag landscape off
flag cardinal_points off
flag show_tui_datetime off
timerate rate 86400
wait duration 120
script action end

It works perfectly and that way there's no need to create a new command.

Lionel RUIZ

[John Cotton (jcotton)]

Lionel - thanks for the suggestion. I tried it and, after a bit of hacking, got it to work. It works as you said, but I tried reactivating the landscape and cardinal points AFTER the time sequence. I set timerate back to 1. When the landscape and cardinal points reappeared the horizon was all kinds of cockeyed. While the sequence worked, it is still not the equivalent of simply suppressing daily motion and leaving the horizon in place.

I was trying to determine if a sequence from my Digistar Christmas show could be converted to Stratoscript. Last night's tests convinced me that it cannot be done. The granularity of control required is too fine.

I'll shut up for now. Thanks for all the advice.

John Cotton

[Lionel RUIZ (astro2kpremium)]

It's normal that things get cockeyed afterwards as you're linked to the sky and not to the ground.
To go back the feet on earth you have to zoom out with the remote in realtime mode or do it by script:

zoom auto out

I'm pretty convinced that aside the perfect smoothness of the movements of the E&S software you can do whatever with nighshade commands. Even things that the Digistar can't do !
Christmas is not that close, it let you plenty time to do the script. If I can be of some help... (<email address hidden>)

Lionel RUIZ