| |
Main
Date: 31 Aug 2006 01:58:36
From: Terry B
Subject: Calculating orbits
|
Dear All
I was wondering how you calculate orbits. I can put orbital elements on
SkymapPro and generate the position of an asteroid etc but how do you do the
reverse?
i.e. I photograph an object like a comet or asteroid over some time and
reduce the positions. With this info how do you work out the orbital
parameters? How many observations are needed over what range of the orbit?
Thanks all
Terry B
Armidale
Australia
|
|
| |
Date: 31 Aug 2006 15:55:17
From: Llanzlan Klazmon
Subject: Re: Calculating orbits
|
"Terry B" <bohlsen@optusnet.nospam.com.au > wrote in
news:gnrJg.20600$rP1.7341@news-server.bigpond.net.au:
> Dear All
> I was wondering how you calculate orbits. I can put orbital elements on
> SkymapPro and generate the position of an asteroid etc but how do you do
> the reverse?
Karl Gauss figured out a method for doing this way back when. I believe his
method is still commonly used. From memory you need at least three separate
observations to calculate the orbital elements. There is lots of software
around that will do the necessary calculations. Project Pluto have a
program called ORB:
http://www.projectpluto.com/find_orb.htm
Klazmon.
> i.e. I photograph an object like a comet or asteroid over some time and
> reduce the positions. With this info how do you work out the orbital
> parameters? How many observations are needed over what range of the
> orbit? Thanks all
>
> Terry B
> Armidale
> Australia
>
>
>
|
| | |
Date: 31 Aug 2006 09:42:44
From: Paul Schlyter
Subject: Re: Calculating orbits
|
In article <Xns9830A1F5F5AE3Klazmonllurdiaxorbgo@203.97.37.6 >,
Llanzlan Klazmon <Klazmon@llurdiaxorb.govt > wrote:
> "Terry B" <bohlsen@optusnet.nospam.com.au> wrote in
> news:gnrJg.20600$rP1.7341@news-server.bigpond.net.au:
>
>> Dear All
>> I was wondering how you calculate orbits. I can put orbital elements on
>> SkymapPro and generate the position of an asteroid etc but how do you do
>> the reverse?
>
> Karl Gauss figured out a method for doing this way back when. I believe his
> method is still commonly used. From memory you need at least three separate
> observations to calculate the orbital elements. There is lots of software
> around that will do the necessary calculations. Project Pluto have a
> program called ORB:
>
> http://www.projectpluto.com/find_orb.htm
>
> Klazmon.
Gauss' method, using three positions (which he btw invented shortly after the
discovery of Ceres and when it had been lost in the glare of the Sun - thanks
to Gauss new method, Ceres was recovered about one year later), is only
the start. What you really want to do is to use as many positions as you
can, to produce orbital elements as accurate as possible. In practice,
you do like this:
1. Choose 3 positions, as widely spaced as reasonably possible, to
obtain the first preliminary orbital elements using Gauss' method.
2. Use the elements obtained in 1) as a first guess of the orbit.
Then use all available observations and do a least-squares fit of the
orbital elements to these positions.
3. Iterate step 2), using the elements from the previous iteration as start
values, until the orbital elements no longer changes significantly.
>> i.e. I photograph an object like a comet or asteroid over some time and
>> reduce the positions. With this info how do you work out the orbital
>> parameters? How many observations are needed over what range of the
>> orbit? Thanks all
>>
>> Terry B
>> Armidale
>> Australia
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
|
| | |
Date: 31 Aug 2006 05:35:24
From: Terry B
Subject: Re: Calculating orbits
|
"Llanzlan Klazmon" <Klazmon@llurdiaxorb.govt > wrote in message
news:Xns9830A1F5F5AE3Klazmonllurdiaxorbgo@203.97.37.6...
> "Terry B" <bohlsen@optusnet.nospam.com.au> wrote in
> news:gnrJg.20600$rP1.7341@news-server.bigpond.net.au:
>
> > Dear All
> > I was wondering how you calculate orbits. I can put orbital elements on
> > SkymapPro and generate the position of an asteroid etc but how do you do
> > the reverse?
>
> Karl Gauss figured out a method for doing this way back when. I believe
his
> method is still commonly used. From memory you need at least three
separate
> observations to calculate the orbital elements. There is lots of software
> around that will do the necessary calculations. Project Pluto have a
> program called ORB:
>
> http://www.projectpluto.com/find_orb.htm
>
> Klazmon.
Thank you. I haven't stumbled on the project pluto site before. Very
interesting.
Terry B
> > i.e. I photograph an object like a comet or asteroid over some time and
> > reduce the positions. With this info how do you work out the orbital
> > parameters? How many observations are needed over what range of the
> > orbit? Thanks all
> >
> > Terry B
> > Armidale
> > Australia
> >
> >
> >
>
|
| | | |
Date: 31 Aug 2006 07:04:44
From: Chris L Peterson
Subject: Re: Calculating orbits
|
On Thu, 31 Aug 2006 05:35:24 GMT, "Terry B"
<bohlsen@optusnet.nospam.com.au > wrote:
>Thank you. I haven't stumbled on the project pluto site before. Very
>interesting.
Of course, it's only a minor project now <g >.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
|
| | | | |
Date: 31 Aug 2006 07:29:41
From: Eugene Griessel
Subject: Re: Calculating orbits
|
Chris L Peterson <clp@alumni.caltech.edu > wrote:
>On Thu, 31 Aug 2006 05:35:24 GMT, "Terry B"
><bohlsen@optusnet.nospam.com.au> wrote:
>
>>Thank you. I haven't stumbled on the project pluto site before. Very
>>interesting.
>
>Of course, it's only a minor project now <g>.
>
For the moment. I read in today's "Nature" that opposition is rapidly
building up against the IAU's decision. I don't think the last words
have been written on the subject!
Of course Pluto is totally unaware of all the fuss and blithely
continues to be what it always has been despite the machinations of
pesky Homo sapiens. <g >
Eugene L Griessel
If we wish to make a new world, we have the materials ready
the first one too, was made out of chaos.
|
| |
Date: 30 Aug 2006 23:54:40
From: Greg Neill
Subject: Re: Calculating orbits
|
"Terry B" <bohlsen@optusnet.nospam.com.au > wrote in message
news:gnrJg.20600$rP1.7341@news-server.bigpond.net.au...
> Dear All
> I was wondering how you calculate orbits. I can put orbital elements on
> SkymapPro and generate the position of an asteroid etc but how do you do the
> reverse?
> i.e. I photograph an object like a comet or asteroid over some time and
> reduce the positions. With this info how do you work out the orbital
> parameters? How many observations are needed over what range of the orbit?
> Thanks all
Some books you might want to get your hands on:
Fundamentals of Astrodynamics (Bate, Mueller, White)
Methods of Orbit Determination for the Microcomputer
(Dan Boulet).
Theoretically, an orbit can be determined from as
few as three distinct position measurements (or
two if the orbit has a known conic section form
and lies in a known plane such as the ecliptic).
But there is generally too much uncertainty in
so few data points to achieve an accurate orbit
good for position prediction over any significant
time period.
Some things to Google while you wait for the
books :-) :
Orbit determination
method of Gauss
Herget's method
|
| |
Date: 31 Aug 2006 10:14:46
From: oriel36
Subject: Re: Calculating orbits
|
Terry B wrote:
> Dear All
> I was wondering how you calculate orbits. I can put orbital elements on
> SkymapPro and generate the position of an asteroid etc but how do you do the
> reverse?
> i.e. I photograph an object like a comet or asteroid over some time and
> reduce the positions. With this info how do you work out the orbital
> parameters? How many observations are needed over what range of the orbit?
> Thanks all
>
> Terry B
> Armidale
> Australia
The celestial sphere geometers here calculate the orbital displacement
for Earth is a constant .986 degrees -
http://www.pfm.howard.edu/astronomy/Chaisson/AT401/IMAGES/AACHCIR0.JPG
This determination is based on axial rotation to the Sun in 24 hours
and the return of a star to a meridian in 23 hours 56 min 04 sec.
As this system of a given star returning to a terrestial meridian
requires a leap adjustment requiring 3 years of 365 days and 1 year of
366 days you can imagine it is not a good way to consider the Earth's
orbital motion around the Sun over the course of an annual orbit.
Of course you can go along with the bluffing,take up a noisy
'definitional' stance and buy yourself a cool star trek outfit to show
you are a dead serious celestial sphere astrologer.
|
| | |
Date: 02 Sep 2006 12:17:39
From: Terry B
Subject: Re: Calculating orbits
|
"oriel36" <geraldkelleher@yahoo.com > wrote in message
news:1157044486.649478.103160@h48g2000cwc.googlegroups.com...
>
> Terry B wrote:
>
>> Dear All
>> I was wondering how you calculate orbits. I can put orbital elements on
>> SkymapPro and generate the position of an asteroid etc but how do you do
>> the
>> reverse?
>> i.e. I photograph an object like a comet or asteroid over some time and
>> reduce the positions. With this info how do you work out the orbital
>> parameters? How many observations are needed over what range of the
>> orbit?
>> Thanks all
>>
>> Terry B
>> Armidale
>> Australia
>
> The celestial sphere geometers here calculate the orbital displacement
> for Earth is a constant .986 degrees -
>
> http://www.pfm.howard.edu/astronomy/Chaisson/AT401/IMAGES/AACHCIR0.JPG
>
> This determination is based on axial rotation to the Sun in 24 hours
> and the return of a star to a meridian in 23 hours 56 min 04 sec.
>
> As this system of a given star returning to a terrestial meridian
> requires a leap adjustment requiring 3 years of 365 days and 1 year of
> 366 days you can imagine it is not a good way to consider the Earth's
> orbital motion around the Sun over the course of an annual orbit.
>
> Of course you can go along with the bluffing,take up a noisy
> 'definitional' stance and buy yourself a cool star trek outfit to show
> you are a dead serious celestial sphere astrologer.
Sorry, you have lost me there. I think you need to invest in a foil hat!
Terry B
>
|
| |
Date: 02 Sep 2006 05:24:09
From: oriel36
Subject: Re: Calculating orbits
|
Terry B wrote:
> "oriel36" <geraldkelleher@yahoo.com> wrote in message
> news:1157044486.649478.103160@h48g2000cwc.googlegroups.com...
> >
> > Terry B wrote:
> >
> >> Dear All
> >> I was wondering how you calculate orbits. I can put orbital elements on
> >> SkymapPro and generate the position of an asteroid etc but how do you do
> >> the
> >> reverse?
> >> i.e. I photograph an object like a comet or asteroid over some time and
> >> reduce the positions. With this info how do you work out the orbital
> >> parameters? How many observations are needed over what range of the
> >> orbit?
> >> Thanks all
> >>
> >> Terry B
> >> Armidale
> >> Australia
> >
> > The celestial sphere geometers here calculate the orbital displacement
> > for Earth is a constant .986 degrees -
> >
> > http://www.pfm.howard.edu/astronomy/Chaisson/AT401/IMAGES/AACHCIR0.JPG
> >
> > This determination is based on axial rotation to the Sun in 24 hours
> > and the return of a star to a meridian in 23 hours 56 min 04 sec.
> >
> > As this system of a given star returning to a terrestial meridian
> > requires a leap adjustment requiring 3 years of 365 days and 1 year of
> > 366 days you can imagine it is not a good way to consider the Earth's
> > orbital motion around the Sun over the course of an annual orbit.
> >
> > Of course you can go along with the bluffing,take up a noisy
> > 'definitional' stance and buy yourself a cool star trek outfit to show
> > you are a dead serious celestial sphere astrologer.
>
> Sorry, you have lost me there. I think you need to invest in a foil hat!
>
> Terry B
> >
Have a ball trying to fit the .986 degree orbital displacement of the
Earth into an elliptical framework representing Keplerian orbital
geomtery -
http://www.pfm.howard.edu/astronomy/Chaisson/AT401/IMAGES/AACHCIR0.JPG
http://www.mhhe.com/physsci/astronomy/fix/student/images/04f15.jpg
If you had intelligence you would go insane or develop a distinct
antipathy towards the silly celestial sphere justification using the
Earth's axial and orbital motions therefore I do not insult you,you
insult yourselves willingly.
No doubt that your 'sidereal' ideas of the Earth travelling faster
along its orbital circumference the further its position was from the
Sun (due to the constant .986 degree angle) must seem like the
greatest thing ever but I have'nt really credited empirical theorists
with an abundance of intuitive intelligence for many years and I
suspect all this would go right over your simpleminded head.
|
|
