Date: Wed, 11 Feb 2004 09:27:32 -0800
From: Russell E Owen
Subject: Re: 2.5m obslog 20040210 (MJD 53046)
At 2:04 PM +0000 2/11/04, Atsuko Kleinman wrote:
>We  found the problem we saw in engCam last night is still with us.  We
>pointed to an fk5 star and then applied the correction as TCC measured
>from its position. The star started to move away from the center of the
>chip instead of putting it in the middle of the chip -- as if the
>offsets had the wrong sign. This was exactly the same behavior we saw
>last night.
It sounds as if the camera is mounted 180 degrees (relative to which
corner is read out) from what the TCC expects.
Note that any time the eng camera is worked on (anything that would
affect the position of the CCD relative to the kinematic blocks) one
should get a new inst block.
Swapping out one camera for another identical version is enough to
justify a new instrument block. The most biggest issue is that a
different corner of the CCD may be read out, leading to exactly the
problem being described. But even without that, the CCD may not be in
a slightly different position, leading to small errors.
Even remounting the same camera is probably enough to justify a new
inst block, unless the repeatability of the mounting is really good.
-- Russell
P.S. I vaguely recall that the eng camera was actually replaced with
an entirely different model (with a bigger CCD). If so, was a new
inst block taken for that?