Re: date error occurs during April 2004

["Gary W. Billings" <obs681@telusplanet.net>]

Good, and FAST work Michael!  It sounds like you are ahead of us as Tom,
Mike, and I were starting to discuss ways to do this routinely.  I'm very
willing to help, but it seems like you have it well in hand.

g.

P.S.  must attend to errands here soon, so will be off-line.


----- Original Message -----
From: "Stupendous Man" <richmond@stupendous.cis.rit.edu>
To: <tass@listserv.wwa.com>
Cc: <mwrsps@rit.edu>
Sent: Saturday, June 12, 2004 8:03 AM
Subject: date error occurs during April 2004


>
>   Following Gary Billings' idea of using asteroid positions
> to check the date in Mark IV data, and Richard Miles' suggestion
> of 739 Mandeville during April, 2004, I find the following:
>
>         real date and time                  Mark IV date and time
>
>     Apr  2 UT (JD 2453096.86)       Mark IV position matches JPL ephemeris
>
>     Apr 14 UT (JD 2453109.82)       Mark IV position from "JD 2453108.82"
>                                             matches JPL ephemeris
>
>     Apr 15 UT (JD 2453110.83)       Mark IV position from "JD 2453109.83"
>                                             matches JPL ephemeris
>
>
>     Apr 26 UT (JD 2453120.79)       Mark IV position matches JPL ephemeris
>
>
>
>   In all these detections, the Mark IV database showed detections
> at the asteroid's position only on the given date and time; in other
> words, I wasn't confusing ordinary stars for the asteroid.
>
>   So, I conclude that the Mark IV database has an "off-by-one-day"
> error for _part_ of the month of April, 2004.  This suggests to me
> a problem with the clocks on the computers, rather than with the software
> which calculates JD.
>
>   I need to write a script to go through _all_ the Mark IV data
> and search for asteroids in order to see if this is the only
> date-and-time problem in the database.  Michael Sallman's
> database interface will help greatly.
>
>   More later.
>
>                                              Michael Richmond
>
>