RFBG Commissioning with Adaptive Secondary - 30 March 2010 UT

Night 11:

Observer: JHeidt, JHill (LBTO)
Telescope Operator: WWack
Software: TEdgin
Instrument Support:: JMorris
Telescope Support: JLittle
Adaptive Support: GBrusa (LBTO)

Summary

Night was hampered by various and varying amounts of cirrus and clouds. One hour not useful at all, half a night seriously hampered. Seeing partly good, but interlaced by short-term periods of bad seeing.

Collimation works at high elevation but does not work at all at elevations below 35deg

Took a set of field aberration measurements (-40" tip), some them are hampered by scattered (moon)light

Took a set of transformation data with varying seeing between 0.6 - 1.4" (on guider)

John's synopsis of current problems

Here's a sleepy attempt to summarize our current list of problems:

1) The biggest problem is that active optics (with both GCSR and IDL) does not converge below elevations of ~35 degrees. At high elevation everything works fine at all field positions. All the flips and rotations are correct (except see problem 3). At 30 degrees, we don't get convergence for on-axis stars. See if you can explain wfsc000050.fits from about midnight.

2) From night to night we find that a variable amount of M2 vertex tip-tilt is needed to get rid of coma. This makes problems for measuring field aberrations, or if we leave M2 fixed and correct coma with M1 we run out of range.

3) The fixed field aberrations still need to be compensated in IDL and GCS. This one is simple once Doug has enough sleep.

4) We still have the obvious scalloping at the edge of shell. It is not known if this is somehow contributing to problem 1) or not.

Preparations

Single frame names refer to: irtc.20100330.xxxxxx.fits

Cube names refer to: irtc.20100330_00xxx_cube.fit

Plan for the night (seeing dependent): Work on collimation issues, collect field aberration measurements (40" tip) and some more transformation data

Details

Open

01:47 Open, lots of cirrus + a few thicker clouds, T_out = 5.7C, T_Mirror = 5.5C, Hum = 4%, no wind

Initial Pointing and Collimation Adjustment

One of the actuators gave bad readings, Guido took care of that. Seems that it is only a problem at EL=90

Each night in this RFBG commissioning run, we go to a bright star (Pollux) at Elevation 80 degrees. Then we adjust the vertex tip-tilt (RX/RY) of the secondary to get rid of the coma that we see in the extrafocal pupil on the IRTC.

02:14 pointto Pollux gs=0, TelM = track, PAMode=no, no star, adjust to yesterday values (CA=-77, IE=-48), EL = 78, do ptspiral, OK, star there, adjust *CA=-68 ,IE=-85*
DX M2 Global X = 2.5, Y = -3.63, Z = 1.77, RX = -360, RY = -120 , coma, adjust to X = 2.3, Y = -3.36, Z = 1.77, RX = -600, RY = -120, CA=-68, IA=-40*

02:31 pointto M5_1210 gs=0, TelM = track , EL = 27, AZ = 170, at very-low elevation to adjust AZ-zeropoint, pointing OK, star found, Adjust IA = -411, keep IE=-40, CA = -68. little big of Coma, hardly any astigmatism, changed Z = 2.35 to be a bit better in focus

Investigating the collimation problem

02:50 pointto M5_1210, GS=4, TelM=active, astigmatism, does not really collimate,

02:56 pointto M5_1210, GS=2, TelM=active, redo with different GS, same (astigmatism, does not really collimate)

03:05 pointto M5_1210, GS=0, telM=Track, adjust global offset , set RX=-760, IE=-25

03:14 pointto M5_1210, GS=4, TelM=active, to see if its collimating now

03:24 cleared C00 + active collimation

03:30 Changed global offsets: RX=-460, RY=50

03:40 started FWS, not converging well at all

03.50 Stopped WFS from GCS, switched to IDL, AGW_collimate_Loop, IDL believes to have converged, star looks still elliptical, WFS-image 5

03:57 pointto Pollux, GS=0, TelM=track, cleared active optics, not star, ptspiral, CA=-38, IE=-75, global offsets are: X=2.5, Y=-2.36, Z=2.3, RX=-500, RY=50

04:11 takeseq t=0.02 seq, for Guido, 041217 cube 97

04:14 BS9143 GS=0, TelM=active, converges pretty well, guider reports 0.8", stop WFS at GCS, switched to IDL, AGW_collimate_Loop, IDL

04:26 BS9143 GS=17, TelM=active, GS looks round from the very beginning, converged quick, guider reports ~0.7", RMS@WFS < 200, stop WFS at GCS, switched to IDL, AGW_collimate_Loop, WFS-image 16

04:40 JHill sends Z9=+500 to the star, starting with WFS-image 24, IDL corrected - 313 at Z9, and none at z10, i.e. fine!

04:43 JHill sends Z10=+500 to the star, starting with WFS-image 29, IDL corrected fine!

04:47 BS9143 GS=17, PA=120 (off the Y-axis by 50degs), TelM=active

04:50 JHill sends Z9=+500 to the star

05:00 JHill sends Z10=+500 to the star

05:03 Collimation via IDL starting with WFS-image 31

05:03 JHill sends Z9=+500 to the star via IDl starting with WFS-image 39

05:03 JHill sends Z10=+500 to the star via IDl starting with WFS-image 42

==> at 60deg elevation collimation works fine

05:16 pointto BS9141, GS=0, TelM=active, GS-image looks ugly, but converges relatively quick even in bad observing conditions (almost full moon and through clouds)!

05:25 pointto BS9141, GS=17, TelM=active, no GS, clouds too thick

05:29 pointto M5_0419, GS=0, TelM=active, low-EL=29, since star is bright adjust Guider-exp-time to 2sec, Ok, than clear C00 to make the star look again ugly...clouds to thick there

05:59 pointto Pollux, GS=0, TelM=active,

06:04 pointto Pollux, GS=0, TelM=track, set RX=-600,

06:14 pointto Arcturus, GS=0, TelM=track,

starts to clear up from the west

06:42 pointto M5_0325, GS=0, TelM=track, CA=-29, IE=-76, EL=-24!, collimates

06:57 JHill sends Z6=+1000

07:01 JHill sends Z9=+300

07:03 Stop WFS with GCSR

07:06 agw_collimate_loop with IDl srarts with WFS-image 49, is WFS getting foolws by moonlight in empty sub-aps?

07:11 JHill sends Z10+300, correcting Z10, but Z9 diverging

07:23 pointto BS9152 GS=0, TelM=active

Field Aberration Measurements on BS9152

Data are in /OldRepository/AGW_Data/20100330 (beware of a second directory 100330)

Lost 1h of WIKI-entries due to network disconnection (and not saving often enough) !!! Most of that time was spent getting our tips and tilts straight, and recovering from bumping into Y-limits on M1.

08:25 pointto BS9152, GS=0, TelM=acquire, PAM=no, center star, IE=-66, CA=-65, tip = -40"

08:40 pointto BS9152 gs=0, TelM=guide, OK centered

M1: Total collimation: *X=1.078, Y=2.264,Z=-0.189, RX=18.958, RY=0.600, RZ=0*
Global offsets: *X-1.331, Y=-0.807, Z=1.0, RX=-11.6, RY=2.5, RZ=0*

M2: Total collimation: *X=2.5, Y=-2.587, Z=1.9, RX=-752.799, RY=-120.0, RZ=0*
Global offsets: *X=2.5, Y=-4.63, Z=1.9, RX=360, RY=-120, RZ=0*

GStar wfscimage#
Sequence 1
0 68 - 73
9 74 - 76
0 77 - 79
17 81 - 83
0 84
18 86 - 88
0 89 - 90
7 91 - 93
0 94 - 95
4 96 - 98
0 99 - 101
1 102 - 104
0 105 - 109
Sequence 2
9 110 - 112
0 113 - 115
17 116 - 118
0 119 - 121
18 122 - 124
0 125 - 126
7 127 - 129
0 130 - 132

image 130 potentially suffers from moonlight (extra photons in the corner)

4 133 - 135

all 3 images have extra photons in the corner

0 136 - 141
1 143 - 145
0 146 - 148
Sequence 3
9 -

Star missed by guider, pretty faint (clouds?)

0 149 - 151
17 152 - 154
0 155 - 157
18 158 - 160

strong additional (scattered) light

0 161 - 163
7 164 - 166

Clouds/scattered light again...stopped

10:33 pointto BS9152 GS=0, TelM=acquire, PAM=no, remove tip

10:41 pointto M5_1396 GS=0, TelM=acquire, PAM=no, centering star, OK

Transformation data

10:51 pointto StoneLagw, GS=0, TelM=active, collimate, seeing on guider ~ 0.8-1

11:00 cl < tran_StoneL_mix1.cl,

PA=0

transtar (35) 110137 cube 98
transtar (31) 110418 cube 989
transtar (21) 110655 cube 100
transtar (19) 110934 cube 101
transtar (15) 111211cube 102

PA=180

transtar (23) 111521 cube 103
transtar (17) 111758 cube 104
transtar (20) 112033 cube 105
transtar (18) 112312 cube 106

PA=45

transtar (35) 112617 cube 107
transtar (31) 112853 cube 108
transtar (13) 113134 cube 109
transtar (24) 113413 cube 110
transtar (30) 113650 cube 111

PA=210

transtar (12) 113957 cube 112
transtar (22) 114236 cube 113
transtar (26) 114514 cube 114
transtar (34) 114750 cube 115

PA=315

transtar (31) 115120 cube 116
transtar (21) 115359 cube 117
transtar (19) 115637 cube 118
transtar (15) 120036 cube 119
transtar (13) 120307 cube 120
transtar (9) 120546 cube 121

PA = 150

transtar (37) 120851 cube 122
transtar (22) 121133 cube 123
transtar (26) 121408 cube 124
transtar (34) 121645 cube 125

12:18 cl < tran_StoneL_mix2.cl

PA = 0

transtar (13) 122004 cube 126
transtar (9) 122240 cube 217
transtar (6) 122518 cube 128
transtar (5) 122754 cube 129

PA = 45

transtar (36) 123038 cube 130
transtar (42) 123321 cube 131
transtar (37) 123604 cube 132
transtar (35) 123843 cube 133

Seeing on guider was between 0.6 and 1.5" throughout the transformation measurements (in general more bad towards the end), not clear to which amount the data are useful. Wind has increased too. Clouds are passing as well.

12:41 Stopped, too bright in the meantime

Close

12:50 Closed, still cirrus, T_out = 2.8, T_Mirror = 3.2, Hum = 23%

Discussion about flattening M2 shell from Guido

Date: Tue, 30 Mar 2010 17:29:34 -0700
Subject: flattening discussion
From: Guido Brusa 
To: John Hill 
Cc: Armando Riccardi 

John,
   this is to summarize the discussions had with you and Armando concerning
the flattening of the adaptive secondary:
1) the shape applied by the shell is dependent on the elevation because of
the variation of the cap sens calibration with the gravity vector.
2) this effect can be mitigated by using the measurement of the differential
pattern of forces applied but only up to a certain (not well defined) level,
in terms of spatial scale. One componenet of forces is required to
compensate a "true" (mechanical) effect on the shell due to change in the
gravity vector, the other is "not true" (electrical) and it is due to
changes to the stray capacitance. To disentangle these two effects is not
trivial.
3) Marco introduced a modal filtering (ho modal offloading) of the forces
that should mitigate the stray capacitance effects but the exact tuning is
still imperfect.
4) The flat is supposed to be 'perfect' only at zenith, this combined with
the fact that we are using the ho modal offloading prevents in principle
from re-flattening the shell at elevation other than zenith (to be verified
may be as early as tonight).

Ciao,
Guido

-- JochenHeidt - 30 Mar 2010
Topic revision: r8 - 27 Apr 2010, JochenHeidt
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