Re: Re:ATM An Old TMs Simple Query

["Mutalib Abdallah" <omegatroid@hotmail.com>]

>From: "Dwight K. Elvey" <dwightk.elvey@amd.com>
>Reply-To: "Dwight K. Elvey" <dwightk.elvey@amd.com>
>To: atm@shore.net
>Subject: Re: Re:ATM An Old TMs Simple Query
>Date: Wed, 22 Jan 2003 15:02:46 -0800 (PST)
>
>
> >From: "Richard Schwartz" <richas@earthlink.net>
> >
> >OK, I have a few schmidt questions...
> >
> >What is a good way to identify the films, index them, and store them?
>
>  Envelopes.

Actually, envelopes are no good at all.  I know a guy who had THOUSANDS of 
images, and eventually scanned them.   Some of the films had been filed in 
the wrong envelope, so he never was able to identify them.  For the rest, he 
built a database that indexed the films with date, time, RA, and dec (to the 
nearest degree).   He always observes from the same location, so that is 
well known.

>   If a field flattener lens is
> >used, what is a good way to remove distortion from the image, and to 
>correct
> >measurements on the distorted image (assuming the exact center of the 
>image
> >is not located).
>
>  I'm not sure there is a way, inless you also projected a grid into
>your telescope with a small lens that you knew had no distortion,
>when used to project at infinity. This could be done with a LED,
>grid mask and a lens. The grids image on the film could be used
>as a reference. Controlling the brightness of the grid, you should
>be able to keep it from washing out the stars.

If the field is more than a few degrees in diameter, it will contain several 
stars whose position is very accurately known.   If you treat the star 
positions and the image positions as complex variables, you can do some kind 
of conformal mapping of best fit.   But the math involved in doing this is 
not trivial.   Ordinary curve fit methods are limited to one variable at a 
time, and there is an excellent program for this called CURVE EXPERT 
available as shareware on the internet.

> >I think the science value is greatly enhanced when the images can be 
>located
> >in time and space, and stored in a non-destructive way.

There are many who feel uncomfortable with science and prefer to rely on 
supernatural forces.   They WANT to see the data destroyed.  But they 
generally do not rely on supernatural forces to burn libraries and research 
facilities to achieve their level of comfort.

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