Subject: Re: [sdss3-25mlog 658] 2.5m obslog 20120503 (MJD 56051)
From: paul harding
Date: Fri, 4 May 2012 16:31:31 -0400
I verified that the correct guide probe information for the recently =
update guide fibers us being used, so its not that.
I did however notice that the plates that were observed last night =
covered a large range in "drilled for temperature".
The first plates on cartridges 5,8,6,1,4 were drilled for -2.7 degC
Then Cart 3, plate was drilled for +4C.  This would require a scale =
change of 154 parts per million, so the guider
would have been trying to make a large scale change.
Cart 7 was drilled for +11C, so another large scale change of 160 ppm =
would be required to match the telescope to the new plate.
Then the final plate was drilled for 5C=20
Did you have to make large manual corrections to the scale when setting =
up on the last 3 plates?
Was the problem with the guider scale calculations only for a single =
plate or for more than one plate? Did it happen later
in the night for the last 3 plates?
Did the guide stars (a guide star) have large guiding errors when the =
scale variability problem happened?
Was the astigmatism in the out of focus fibers particularly bad at the =
time of the problem?
The seeing was reported as 1.5 arc sec, but the guider exposure times =
were often 5sec, this is not long enough to average
over image motion in poor seeing.=20
I assume that the guide probe data for the recently replaced cartridges =
is correct, otherwise we would have had problems guiding
on previous nights, however can you run a simple test to verify the new =
rotation angles are correct.
Tonight can you verify that the guide fiber rotation data is correct by =
offseting the telescope 2 arc sec from the nominal guiding position
to check the guiding error vectors all point in the same direction for =
each of the recently updated cartridges.
Paul
On May 4, 2012, at 7:56 AM, gebelke@apo.nmsu.edu wrote:
>=20
>                       APACHE POINT OBSERVATORY SDSS 2.5M
>=20
>                                 OBSERVING LOG
>                          Thursday May 03, 2012
>=20
>                                  (MJD 56051)
>=20
>=20
> Guide Fibers
>=20
> We have noticed a problem with the scale changes on the guide fibers =
tonight.
> With the scale correction turned on, the scale jumps around quite a =
lot. It go
> bad enough that the scale correction needed to be turned off and the =
scale was
> still jumping around a lot more than needed. It doesn't appear that =
there were
> any software changes with the guider.
>=20
>=20
>=20