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Does StarGPS for #497 have updated planetary data?

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#1 Taylor

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Posted 03 January 2020 - 05:07 PM

Does anyone know if the StarGPS updated Autostar 497 files include updated orbital elements for the planets? Meade hasn't updated the Autostar 497 in years, but the StarGPS file was updated in 2019.

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#2 OzAndrewJ

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Posted 03 January 2020 - 05:32 PM

Gday Taylor

 

Nope. We never patched the 497s for planetary calcs, only the ASII.

The 2019 patch update was for the GPS rollover bug

 

Andrew Johansen Melbourne Australia



#3 Piet Le Roux

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Posted 04 January 2020 - 01:03 PM

This is why I never sync on planets, they are "wonders". I also delete all original  satellite and comet data in the controller : they are out of date and will just frustrate you. If you use fresh data  you would be surprised how accurate the Autostar/Audiostar is. I have been playing with BASIC programs on to calculate a comet's position from global elements : it is a very complex thing to calculate accurately! And the Audiostar does it well in a few seconds, not bad for 20 year old software!     



#4 Piet Le Roux

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Posted 04 January 2020 - 01:22 PM

PS Meade did released new software in 2019 to solve GPS problems The Audiostar got A4S4  and the 497 also got a update, but I think they only solved GPS problems.



#5 Taylor

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Posted 04 January 2020 - 01:58 PM

Bummer. 

 

I guess by sticking to a iPad with SkySafari connected to Stella, it should provide more accurate goto than the old data in the Autostar. 



#6 Piet Le Roux

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Posted 04 January 2020 - 03:29 PM

I don't see how because you are still going to use the Autostar do a two star alignment and after that is done procession is nearly eliminated and it is only proper motion that will play a role and that is not going to have any effect, Ok the Ra and Dec that the Autostar is going to display will be out by a minute or two thats all. 

 

I did a test on Canopus, its Ra/Dec according to Stellaruim is 6h24m24.5s and -52 degrees 42 minutes and 28 seconds on this date. Meade has it at 

6h23.9 and -52 degrees 41 minutes. But what ever the display say they will be pointing at the same thing.  



#7 OzAndrewJ

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Posted 04 January 2020 - 04:10 PM

Gday Piet

As you note the 497/Audiostars dont do precession, and whilst this doesnt badly affect stars after 2 star aligning,

it does with planets ;-).

Using skysafari etc to do an accurate planet/moon calc will certainly give better results.

Andrew Johansen Melbourne Australia


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#8 Piet Le Roux

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Posted 04 January 2020 - 05:00 PM

Well the "wanderers" basically do their own thing but its a good point you made. The easy ones are not a problem, you just find the ecliptic and then they are easy to spot and I just manually guide to it with the old green laser. But I think its a good idea to save the present J 2000.0  values under "user objects" for the hard to find ones.  



#9 Piet Le Roux

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Posted 05 January 2020 - 01:07 AM

PS I gave this some thought and wondered if one cannot get TLE (two line elements) data for the sun, moon and planets?  then you could program them into the Autostar as asteroids. The answer is no! Our solar system are changing all the time, scary thought, because all the objects in the solar system are having an effect on each other because of their gravity and because they are revolving all the time this effect is constantly changing. I suppose this happens in the rest of the Galaxy but effects are more subtle.This is why the TLE for satellites have a very limited shelf life and have to be updated every two weeks to be accurate. This gives  an better explanation : 

 

https://celestrak.com/columns/v03n03/


Edited by Piet Le Roux, 05 January 2020 - 01:13 AM.


#10 OzAndrewJ

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Posted 05 January 2020 - 01:53 AM

Gday Piet

 

because all the objects in the solar system are having an effect on each other

Yep. The basic planet calcs in the Autostar are very crude and based on a simple solving for keplers method and then applying an interpolated correction table based on a 2 week spacing to tweak it.

If you really want to look at a next level in how to do the calcs to include other orbiting bodies,

look up the VSOP method.

"Astronomical Algorithms 2nd Ed"  by Jean Meeus gives a good run down on it

and it only takes 40 pages in the book to list the terms for the equations :-)

 

Andrew Johansen Melbourne Australia




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