Date: Tue, 30 Nov 2004 08:44:58 -0600
From: French Leger
Subject: RE: 2.5m obslog 20041129 (MJD 53339)
Howard:
There is a way of increasing the air pressure on the instrument latches.
In the cone area there lives a pressure regulator that is labeled
latches and one needs only to increase its output pressure. It's
normally set of 110 psi.
French
-----Original Message-----
From: Pete Newman [mailto:prn@apo.nmsu.edu]
Sent: Tuesday, November 30, 2004 8:16 AM
To: hjbrew@apo.nmsu.edu; obs-report-25m@apo.nmsu.edu
Subject: RE: 2.5m obslog 20041129 (MJD 53339)
The problems with the slit-heads is likely caused by a drop in effective
compressed air pressure to the latches plus the mechanisms becoming
stiff,
which we've seen before at these temperatures.
I recall that there is a way to increase the air line pressure at the
telescope (Jon?  French?) in this situations, but in the past this has
just
moved the problem to another cold-related issue.  Note that the
enclosure
guide
  http://sdsshost.apo.nmsu.edu/sdssProcedures/sdss_closure_guide.html
reports the onset of pnuematic and other problems at -10C (+14F) and
recommends no attempts at operations below -12C (+10F).  The weather
system
reported air temperature in this range at the time of failures.
--Pete
Howard wrote in part:
> After I ventilated the enclosure for about an hour, I started the
spectro
> monthly checkout.  Unfortunately, I had a few problems.
 ...
> I also had a problem while putting plate 666 on cart 08 for the
> spectro darks.
> After retracting the slit-head latches and unlatching the cart, the
cart
> seemed to stick on its southside.  So, I reseated the cart to the
> scope and
> lowered it again. This time, all was well.  The temp in the
> enclosure was about
> -9.5 degrees at the time.  After the darks as I removed plate
> 666, cart 08 did it again, i.e., the southside did not release
properly.
And the weather system logged:
>                              Wind
>       Time   Temp F Dewp F  MPH   Direction    Dust  DIMM   Sky
>
>      01:24Z    11     7      5   354  (NNW)    282     -
>      01:57Z    12     4      8   359  (NNW)    218     -
>      02:27Z    12     1      4   346  (NNW)    180     -
>      02:59Z    12     3      6    26  (NNE)    287     -
>      03:29Z    11     1      8     2  (N)      237     -
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