Date: Sun, 28 Oct 2007 09:54:50 -0600
From: Dan Long
Subject: Re: 2.5m obslog 20071027 (MJD 54401)
>                        APACHE POINT OBSERVATORY SDSS 2.5M
>
>                                  OBSERVING LOG
>                            Saturday October 27, 2007
>
>                                   (MJD 54401)
>
>---=== OBSERVING TEAM ===---
>
>Shannon Watters
>Dmitry Bizyaev
>
>---=== OBSERVING PLAN ===---
>
>SEGUE
>
>---=== OBSERVING SUMMARY ===---
>
>We reverted back to the ole patched up TCC because of the header problems from
>last night.
>
>Photometric skies for the majority of the night.  We acquired signal on 4
>plates (2305, 2815, 2825, 2682) but don't know if they're finished until we
>hear back from B. Yanny.  We couldn't find guide stars on plate 2632 (same
>problem on MJD 54397).
>
    I took a look at guider frame gimg0446 (which was the first guider
frame after going to the fk5 star) and like on 54397 a few nights
ago, I could see very faint guide stars in about half the fibers.
They were extremely faint in the 10 second exposure.  In fact I had
to blink between two frames (using one of the spiral pattern frames
as the non-star frame) to be absolutely sure they were there.
    Does anyone know what the magnitudes of the guide stars for this
plate should be, and how they compare to that of guide stars on other
plates?  It sure looks like they are much fainter than normal, and
may be so faint as to not be guideable.
   If you do attempt this plate again (and it is probably worth
waiting until you hear from someone on the guide star brightness), I
would recommend very long exposure times for the guider (at least 30
seconds) for this plate.
				Cheers,
				  Dan