Determining Adjustment of Right Zero Point (20140430)

MODS2 images are mods2r.20140429.00NN.fits

08:00 Preparing to run a 'Slit Scan':

Doug sent preset to AO503

• collimated, but then changed to track preset before taking MODS2 data.

NN=10 gprobe 0 0
updatepointing
NN=11 gprobe 0 30

NN=12 gprobe 0 0 NN=13 offsetxy 0 30 abs NN=14 offsetxy 0 -30 abs NN=15 offsetxy 0 15 abs NN=16 offsetxy 0 -15 abs NN=17 0.6" slit

Sum images 12-16 (slitscan1.fits), and compute star X,Y centroids (starcen.dat)

Use new modsAlign slit-fitting to determine slit center at 9 positions along the slit (slitcen.dat)

Fits Y vs X yield rotations with respect to vertical of (now from my notes):

• -2.595 deg for starcen.dat
• -0.1455 deg for slitcen.dat

So there is a difference of -2.445 deg between the slit and the Y-offsets. The needed offset to the right zeropoint = -2.445

Changed rightzeropoint from -30 to -27.55
restart PCS

iif_preset, AO503, MODS=ACTIVE, GS=0

• stop guiding
• modsCmd agw reset

Take a pair of images

NN=18 first image on axis NN=19 offsetxy 0 60 abs

Slit was still in, repeat:

NN=20 at offsetxy 0 60 position NN=21 at offsetxy 0 0

==> delta zeropoint was wrong sign.

PA helicity: From MODS1 Commissioning report, if delta_PA is positive, stars will rotate clockwise.

From RotatorAngle:

ROTANGLE x LEFTSCALE = POSANGLE - PARANGLE + (180 - LEFTZEROPOINT)
LEFTZEROPOINT=+27.63
LEFTSCALE=-1.0

Change rightzeropoint to -32.45 deg
restart PCS
resend preset
stop guiding and agw reset

NN=22 at offsetxy 0 0 NN=23 at offsetxy 0 60

Good. Rotator zero point is -32.45 deg.

NOTE: We had continued problems with invalid rotator polynomials. These seem to have stopped when John added 360 deg to the zero point, setting the new rotator zero point to 327.55 deg

-- %USERSIG{OlgaKuhn - 2014-05-01}%

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