# [AstroPy] Meteor Methods--Atmospheric Trajectories, PC Book on Astronmy

Wayne Watson sierra_mtnview@sbcglobal....
Thu Dec 17 16:00:54 CST 2009

```Hi, the problem is very complex. I only cited the book as a reference to
give some idea of how what the plate reduction phase is done for an
ordinary camera.

I think the first solution to the more general method was provided by
Ceplecha in his 1989 paper. He goes into multiple station observations,
ground track, atmospheric track, orbit calculation and more.Our
observations are from two video cameras spaced about 35 miles away.

I was hoping to turn up someone who might be familiar with these ideas.
I've begun working with a pro astronomer who has a fairly decent handle
on these matters, and, I'm at the early stages of trying some methods he
proposed. If nothing else, I think some rough estimates of the two
trajectories can be made without months of coding.

What I find odd about this type of meteor work is that I have yet to see
it mentioned in any book on celestial mechanics. There are a number of
papers on the web, but it takes a bit to understand them. Further, no
one seems to have recently written any code to do the calculations.
Ceplecha wrote a 4000 line FORTRAN program for it all, but it is no
longer available.

Paul Barrett wrote:
> Hi Wayne,
>
> Sorry to take so long to respond. I have not been able to look at the
> book that you referred to on Amazon - I will check it out of the
> library tomorrow, but am quite familiar with the algorithms.  What
> exactly are are you trying to do?  Do you have CCD images that you
> would like to get accurate star positions from, or are you trying to
> use known star positions to accurately measure the position of an
> asteroid or similar object?  These are variations on the same problem,
> but the algorithms differ, i.e., can be simplified, depending on the
> question that you are trying to ask.  The latter problem just requires
> accurately estimating the plate parameters in order to measure the
> object's position.  The size of the matrix depends on the number of
> stars that have been measured and the number of plate or image
> parameters. Of course there is freely available software that can do
> much of this for you. Let me know your exact problem and I'll try to
> provide a more explicit response.
>
>  -- Paul
>
> On Mon, Nov 30, 2009 at 1:26 PM, Wayne Watson
> <sierra_mtnview@sbcglobal.net> wrote:
>
>> I sent a follow up msg that would make this easier; however, the
>> moderator is holding on to it. It had attachments.
>>
>> Wayne Watson wrote:
>>
>>> Perhaps the best way is to refer you to the 2009 edition of the book.
>>> You'll be using the Amazon Search Book facility. They've made it a bit
>>> harder to use, perhaps, but the paragraph below will let you piece
>>> together the critical pages in the astrometry section. I have some these
>>> pages copied from a much earlier book, and this section has definitely
>>> been expanded. The ppmcat portion I finally direct you looks like a big
>>> improvement on the tiny catalog they used in an earlier edition.
>>>
>>> <http://www.amazon.com/Astronomy-Personal-Computer-Oliver-Montenbruck/dp/3540672214/ref=sr_1_1?ie=UTF8&s=books&qid=1259111820&sr=1-1>
>>> See the Look Inside icon on the upper left and enter the word astrometry
>>> when the small dialog window opens up. You will then see the first page
>>> that shows that word. Use the right button to go to the next result.
>>> That is the page that's the start of chapter 12. Now use the right arrow
>>> to move through the pages. I can only get through the first three pages,
>>> but you'll begin to see what they are doing. To go further, do this. Go
>>> back to the search dialog and enter "plate reduction" (no quotes). Skip
>>> to the second result and you should be on page 254. Now use the arrow to
>>> doing. If you care to go on, go back to find again and enter squares
>>> adjustment. Move via next button to 256, then move ahead one page at a
>>> time. By then you should have a good idea of what this is about.
>>>
>>> To get a summary of that section use ppmcat for find. Some of the
>>> summary pages are blocked, but at least you'll get some idea what all
>>> this produces.
>>>
>>> Paul Barrett wrote:
>>>
>>>
>>>> Wayne,
>>>>
>>>> I am not familiar with the book, but your comment about astrometry
>>>> caught my eye.  We are currently implementing the plate reduction
>>>> methods as part of our work, actually on a much larger scale, of order
>>>> one million images.  These calculations should be easy to do in Python
>>>> for just a few images.  The important point is to properly set up the
>>>> arrays. You can then use the routines in scipy to do the least squares
>>>>
>>>> I might be able to help if you can describe you problem in more detail.
>>>>
>>>>  -- Paul
>>>>
>>>> On Tue, Nov 24, 2009 at 4:21 PM, Wayne Watson
>>>> <sierra_mtnview@sbcglobal.net> wrote:
>>>>
>>>>
>>>>
>>>>> Is anyone familiar with some of the mathematical methods for calculating
>>>>> atmospheric trajectories for two stations. Have they been implemented in
>>>>> Python?
>>>>>
>>>>> There's a computer book with the title something like PC Computations
>>>>> for Astronomy. (Ah, Astronomy for the Personal Computer) I believe the
>>>>> latest version provides methods for C++, and earlier editions for older
>>>>> languages. In one of the later chapters the authors delve into what I
>>>>> think is called plate reduction. (Ah, the chapter is titled Astrometry.)
>>>>> The idea is that an image of the night sky is provided and a catalog is
>>>>> examined to identify stars on the image. Has anyone implemented the
>>>>> various algorithms used for this in Python?
>>>>>
>>>>> --
>>>>>
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>>>>>
>>>>>
>>>>>
>>>>
>>>
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>
>

--

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Obz Site:  39° 15' 7" N, 121° 2' 32" W, 2700 feet

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```