From: Craig Loomis
Date: Thu, 30 Jun 2011 11:56:22 -0400
Subject: Re: [sdss3-25mlog 187] Re: 2.5m obslog 20110629 (MJD 55742)
  Thanks, I'll apply that change. The behavior on field acquisition
for cart 11 last night was a bit more inconsistent than I'd think a
~20 degree offset would give, but I think a recent change in the
centerUp command might have made things worse. Basically, centerUp
only looks at any enabled big fibers, applies a single ra&dec shift,
then turns on the three axis correction loop. That last bit is the
change, which we made after concluding that the centering shift was
both safe and effective.  In this case the centering correction didn't
really help pull in other stars and left the two acq fibers with large
but inconsistent errors, and when the corrections were turned on the
loop applied a large (~1500") rotation correction. We should clip that
to something smaller than the probe diameter.
  Cart 11 was the first cartridge of the night, so the scale was way
off. For the 1st acquisition of the night I wonder if centerUp should
not enable the regular loop.
 - craig
On Thu, Jun 30, 2011 at 11:24, Dan Long  wrote:
> =C2=A0 The fiber angles of cartridge 11's acquisition fibers were checked=
 against
> the values on file in gcamFiberInfo.par. =C2=A0Fiber 11 was different by =
7
> degrees. =C2=A0This probably isn't enough to be significant. =C2=A0Fiber =
3 is off by
> 20 degrees (220 on file, 240 measured today). =C2=A0This is enough that i=
t might
> start to affect acquisition efficiency, especially if the starting offset
> from fiber center is large. =C2=A0I've gone ahead and updated gcamFiberIn=
fo.par
> with the new acquisition fiber angles for cartridge 11. =C2=A0If it is de=
cided to
> be enough of a problem to warrant a mid-run change, Craig or Paul could c=
ut
> a new version of the guider.
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Cheers,
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Dan
>
>
>> The rotator offsets mentioned were not with the rotator axis; we didn't
>> have any problems acquiring stars tonight, nor with any less efficiency,
>> other than with cartridge 11 and in this case the acquisition-fiber erro=
r
>> vectors appeared rotated relative to the other guide fibers by some angl=
e.
>> It seems that the acquisition fibers may have slipped (French used the
>> term 'de-laminated') and the fiber rotation angle might be different whi=
ch
>> made acquisition of one star during centerUp more difficult for cartridg=
e
>> 11.
>>
>>
>>> =C2=A0One more thing to add:
>>>
>>> =C2=A0Please check the guide acquisition fibers for cartridge 11 since =
we had
>>> =C2=A0large rotator offsets tonight.
>>>
>>> =C2=A0Thank you.
>>>
>>> =C2=A0Audrey and DanO
>>>
>>>>
>>>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0APACHE POINT OBSERVATORY SDSS 2.5M
>>>>
>>>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0OBSERVING LOG
>>>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 Wednesday June 29, 2011
>>>>
>>>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 (MJD 55742)
>>>>
>>>> =C2=A0---- =C2=A0Observing Team ----
>>>>
>>>> =C2=A0Daniel Oravetz
>>
>> =C2=A0>> Audrey Oravetz
>>>>
>