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Old AAOmega focus routine


The focus process used to be very complex.  Use Will's Hartmann.cl routine:


in IRAF

task hartmann = home$hartmann.cl

-> here home is ~user/iraf/ from within IRAF



The hartmann routine returns 13 shift measuremnsts.

1) an overall estimate of the focsus shift (piston)

2) a 3x3 grid of shioft measures across the detector

3) averages, per column, of the shifts (a sanity check on each measure)

Blue and Red cameras have the shifts inverted due to the xtra mirror in the blue beam.

We need three shifts:

A = spAtial
E = spEctral
P = Piston


An example of the 3x3 grid is


4 0 8
17 -2 10
12 7 13
/|\
 |
Delta _A
 |
-------> Delta_E -->


From this data grid,

D_A ~ -7  (i.e. the shift is -ve from bottom to top)
D_E ~ 0  (i.e. there is no clear large scale shift across the detector)
D_P ~ +14 (i.e. all of the values seem high, by around 10 units)

The units are "centi-pixels" (i.e. 0.12pix  becomes 12)

We calculate the Shifts to apply to the focus mechanisams using:

Shift A = A * D_A
Shift E = E  * D_E
Shift P = P  * D_P

But note that the multipliers are reveresed for each camera.jet bow shocks


Multiplier Blue Camera Red Camera
A -7 +7
E -12 +12
P +0.4 -0.4

Current thinking is that we apply the shifts if D_A or D_E >  |50| and  for  D_P  >  |1|


Sarah Brough (sb@aao.gov.au)