From rayner@galileo.ifa.hawaii.edu Mon Nov  1 09:54:15 1999
Date: Sun, 31 Oct 1999 23:51:40 -1000 (HST)
From: John Rayner <rayner@galileo.ifa.hawaii.edu>
To: bergknut@jeans.ifa.hawaii.edu, denault@jeans.ifa.hawaii.edu,
    gching@galileo.ifa.hawaii.edu, kuwata@jeans.ifa.hawaii.edu,
    neill@galileo.ifa.hawaii.edu, onaka@jeans.ifa.hawaii.edu,
    rayner@galileo.ifa.hawaii.edu, rayner@galileo.ifa.hawaii.edu,
    toomey@jeans.ifa.hawaii.edu, vern@hokuhele.ifa.hawaii.edu,
    watanabe@jeans.ifa.hawaii.edu

Everything appears to have gone well with the cooldown
and initial cold tests.

We have a slight leak in the epoxy of one of the
cable feedthroughs. This was temporarily plugged
with putty. Cooling went fine. We used a pressure
fill. This seems adequate to get the LN2 can cold
enough to collect LN2 but at no stage did we manage
to fill the can, I had to resort to hand filling to
do this. Vacuum pressure is 1x10-7torr!

With two qualifications all the mechanisms work. I let
things cool for 48hrs before moving anything. We know 
we have problems with the spectrograph focus but it
moves OK cold. I've moved it about twenty times. Two times
the commandered position differed from the actual position
by one step (eg. +200,000 vs +199,000) and the following
move produced an error which was corrected by an init. So
we might be losing the odd step. I also noticed that
although no error was reported, the dichroic open position
was several degrees off in position a couple of times.
Rotator, grating, slit and the two filter wheels are all
working fine.

The guider cold focus looks good - the 2.5 pixel slit is
producing 3 pixel-wide images. The spectrograph focus is
very good although I had to move it from -100,000 steps
to +300,000 steps (4mm), which is 2mm more than predicted.
This puts the focus right at the limit so we'll need to
move the focus stage 2mm closer to the lens to place the
focus closer to the middle of the travel.

There was a 30-pixel shift of all the spectra in the long
wavelength direction after cooling and a 100 pixel shift
along the slit direction. The shift along the slit direction
is corrected by rotating the grating turret very slightly.
These shifts are probably due to a slight tilt on the
grating turret as it cools. (Four of the five spectrograph
modes are installed.)

There was no difference in the warm and cold positions
of the slits on the guide array. The rotator axis did
not change either.

Both muxes are being controlled at 30.00K are are working
fine.

I don't plan to do any further testing until Thursday since
I have to work on MOWG stuff for Bob (who leaves Wednesday 
night). I'll warm up over next weekend. I think we need to
do one more cooldown with the muxes before putting in the
science arrays. Mods:

1) Fix spectrograph focus mechanism
2) Move spectrograph focus 2mm closer to lens
3) Change dichroic software and/or spring
4) Metrology of muxes in array mounts so that we
   know precisely where to put science arrays


Thanks,

John