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Re: Astrometry errors

On Fri, 3 Nov 2000 14:07:49 -0500 (EST), Doug Welch <welch@physics.mcmaster.ca> wrote:
*>
*>What is believed to be the main source of astrometry errors
*>in the TASS scans (besides quality of focus)? Is there a 
*>secular drift in a single coordinate or is it a focal length
*>scale change (or both?) Could someone direct me to the
*>best, most recent summary in the archive if this question
*>has already been answered 12 times?!
*>
*>Cheers,
*>Doug

Is this in regards to the results per image, or accumulative results
in some of the TASS-based databases? The Tech NOtes would be the
first place to look in either case, then the email archives as leads
dictate.

My recollection is that astrometry was discussed most often in conjunction
with discussion of the results and review of Michael Richmond's TENXCAT
efforts. YOu might try a word search of the TASS email archives around
the date of that discussion: use the dates on Richmond's Tech Note
on Tenxcat as the email is archived by month. Read his TN for some
information.

Each Mark III site reduced its own data, generally with their own software.
Check those sites' Web pages for some info in that regard; also sections
of the TASS Web site corresponding to those sites or their reduction software.
My Tech Note #57 chronicles Mark III sites and their software, and also
has WEb pointers to the appropriate Web sites (as of last update to that note).
My TN will not include other TASS members who have also written reduction
software but do not have Mark III cameras - Andrew Bennett comes to mind -
but a search on email will find those participants.

Keep in mind that Mark IV is a completely different camera, so it's imaging
and thus its astrometry will be different. Estimates have been discussed.
Also the software for Mark IV
is still early in development: you might use Mark III software methods
as a clue to what will be used on Mark IV, or see what the software
authors have to say.

Herb Johnson

Herbert R. Johnson              http://pluto.njcc.com/~hjohnson
hjohnson@pluto.njcc.com         voice 609-771-1503, New Jersey USA
             amateur astronomer and astro-tour guide
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