Date: Mon, 27 Oct 2003 13:15:51 -0700
From: Dan Long
Subject: Re: 2.5m obslog 20031026 (MJD 52939)
>                        APACHE POINT OBSERVATORY SDSS 2.5M
>
>                                  OBSERVING LOG
>                             Sunday October 26, 2003
>
>                                   (MJD 52939)
.
.
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>
>The Apache Wheel scans quickly filled the arch tapes, so we put in a
>fresh set.
    I am a little puzzled by this.  It is the second time when doing a
substantial amount of Apache Wheeling in a given night that the tapes
have filled.
    The data rate should actually be less than normal imaging.  The
scan rate is ~7 sidereal, and binned 4x4 the read rate is 1/16.
Multiplying the two gets a data rate about half of normal sidereal
scanning.
    With the frames now made very long to get about the same amount of
data per frame, the archiver should be loafing along.  In fact I
remember seeing it idle significantly more often while taking AW data
than normal imaging (though I haven't looked recently).
    So what is filling up the tapes?  Is there still some  frame or
block size issue in the DA which is apportioning substantial blank
space on the tapes?
				Cheers,
				  Dan