From rayner@galileo.ifa.hawaii.edu Mon Dec 20 08:07:27 1999 Date: Sun, 19 Dec 1999 18:10:54 -1000 (HST) From: John Rayner 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, toomey@jeans.ifa.hawaii.edu, vern@hokuhele.ifa.hawaii.edu, watanabe@jeans.ifa.hawaii.edu Please read and comment. Now that we have longer handles I was able to tilt the cryostat in all the relevant axes: Equiv tel orientation* GT /pixels slit/pixels dx dy dx dy 60 degr towards west -2.0 0.0 -0.5 0.0 +/- 0.25 pixels 60 degr towards east +0.5 0.0 0.0 0.0 " 60 degr towards north -0.5 0.0 0.0 0.0 " 60 degr towards south -0.75 0.0 0.0 0.0 " *SpeX stowed on east MIM mount with electronics box facing east. Three out four within spec! (Note: the north and south GT movements don't change direction as you might expect.) (One way to reduce the effects of flexure, since telescope tracking on an object moves east to west, would be to mount SpeX with the electronics box pointing south. We could do this by mounting on the south MIM port which the day crew want to reserve for visitor instruments. Comments!?) So the axis we've been fixating is also the worst. This is also the only axis we see any measureable slit movement. Tilting towards the west is the only direction which compresses the slit wheel axial spring so this explains the slit movement. It's so not easy to see how this movement can cause a wavelength shift (dx) in the spectrograph but it's probably worth bracing the slit wheel and remeasuring the movement. If this works then it's worth stiffening the slit wheel spring some more. Apart from this potential mod I'm now satisfied with the flexure assuming nothing untoward happens cold. Plan for this 'week' Cryostat Rotate cryostat and remove vacuum cover (Greg) Brace slit remeasure flexure (John and Vern) Possible slit removal and mod (Greg) Reassemble and place on turbo (Greg) Vacuum test (Greg) Cooldown (John) Test dewar Cold test mux to check out new controller boards? (Peter) Cold test science array? (Peter) Thanks, John