Re: double checking dates on Disk 18

[Tom Droege <tdroege@veriomail.com>]

One reason for sending out this data was to that problems like this could 
be fixed.  This reminds me that there is still another error.

OK, disk 18a was from a run which started at local date 010412 at 
23:22.  This puts it on the 13th universal time (I think).  So DATE-OBS 
looks right as to date.  Note that I compute DATE-OBS.  There is also DATE 
in the fits header that is computed by Rob.  It differs from my DATE-OBS by 
one hour.  We are yet to settle who is right.  There is also a UT in the 
fits header which I compute so (not surprisingly) it agrees with DATE-OBS.

Rob computes the hiraxxxxxxx.fits label, which I then normally use to write 
the range of files on the CD faces.

So to answer your questions:

The run started at 23:22 local time on April 12, 2001.  Disk 18a was made 
from the second data disk I took that night so it would have started at 
about 01:12 on April 13th.

There is a two day gap before 16b which I have starting on the evening of 
the 15th with no time in the log.

I note that I never write enough things in the log.  One thing we should 
develop is a log sheet with blanks to fill in.  One thing I have been 
trying to do for these runs is to set the computer clock to a few 
seconds.  I do this at least every few days over this run.  It was seldom 
out by more than a few seconds.

I hope that this helps.

Tom Droege


At 05:33 PM 5/25/01 -0400, you wrote:

>   Tom,
>
>     I've been examining the Disk 18 data.  I see an inconsistency
>in the dates.  The FITS header records a UT date and time, for
>example:
>
>        data disk 18a   hira2011752.fits    says
>                        DATE-OBS= '2001-04-13T06:02:55'
>
>     Now, April 13 06:02:55 UT corresponds to Julian Date 2452012.752.
>I've checked this in two different ways.
>
>     But the name of the file, "hira2011752.fits", would indicate
>that it was taken on Julian Date 2452011.752.  That's one day
>earlier than the date indicated by the FITS header values.
>
>     Perhaps this has been noted already.  But could you please
>double-check for me the following:
>
>        data disk 18a   has data which indicate clouds early and
>                        mostly clear skies late in the night.
>                        There is a three-day gap between it and
>                        data disk 18b.
>
>        Could you tell me exactly when you took the data on disk 18a?
>
>
>     If you can say, "the night starting Thursday, April 12,"
>or "the night starting Friday, April 13", it will help me to
>make sure that I'm interpreting things properly.  At the moment,
>I'm using the FITS header values, and ignoring the file name.
>
>                                            Michael
>
>
>