European Organisation
for Astronomical
Research in the
Southern Hemisphere
Organisation Européenne
pour des Recherches
Astronomiques
dans l’Hémisphère Austral
Europäische Organisation
für astronomische
Forschung in der
südlichen Hemisphäre
VERY LARGE TELESCOPE
Adaptive Optics Facility
HAWKI /GRAAL
Exposure Time Calculator
VLT-SPE-ESO-22200-6100
Issue: 1
Date: 27.01.2015
Function
Author
Name
Ralf Siebenmorgen
Jerome Paufique
Approver
Robin Arsenault
Releaser
Luca Pasquini
Date
Signature
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
HAWKI/GRAAL
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REVIEWERS
Reviewers
Affiliation, Division
IOT: GCA,EVA,HKU,JPA
ESO
Jakob Vinther
ESO
CHANGE RECORD
ISSUE
DATE
0.1
0.2
18.02.14
21.10.2014
0.3
0.9
1
20.01.2015
15.10.2014
27.01.2015
SECTION/PAR
A.
AFFECTED
all
ETC formulae
and comparison
All
Sect. 6
minor updates
REASON/INITIATION
DOCUMENTS/REMARKS
Initial draft, RSI
JPA
for review RSI
Jerome Paufique
RSI
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TABLE OF CONTENTS
1 Introduction ............................................................................................................ 4
1.1 Scope ............................................................................................................. 4
1.2 List of Applicable and Referenced Documents............................................... 4
1.3 List of Abbreviations & Acronyms................................................................... 5
2 Introduction ............................................................................................................ 6
2.1 Instrument overview ....................................................................................... 6
2.2 HAWKI combined with GRAAL ...................................................................... 7
3 Observing modes................................................................................................... 8
4 Performance Improvement for SCIENCE .............................................................. 8
5 The existing HAWKI ETC ...................................................................................... 9
6 Model for AO correction ....................................................................................... 10
7 ETC upgrade: Specifications ............................................................................... 11
8 Appendix .............................................................................................................. 14
8.1 GRAAL performance estimates: ETC versus Octopus ................................. 14
8.2 Octopus simulations ..................................................................................... 14
8.3 Exposure time calculator .............................................................................. 14
Open-loop comparison: ..................................................................................... 15
8.4 Use cases for AO correction ........................................................................ 16
8.5 Further comparisons of AO performance estimates. .................................... 18
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Introduction
1.1 Scope
This document specifies the exposure time calculator to be used for all supported
observing modes for the combined HAWKI/GRAAL instrument at the VLT using the
adaptive optics facility (AOF).
For a description of the HAWKI instrument see the User Manual (R2). The calibration
of HAWKI without AOF/GRAAL is given in the calibration plan R1. This plan was
slightly updated in context of the HAWKI closeout calibration plan (R6). For the
templates to be used see the template design document (R3). It is foreseen that this
plan will be updated after commissioning of GRAAL and the combined
HAWKI/GRAAL instrument. The respective commissioning plans are described in R4
and R5.
1.2 List of Applicable and Referenced Documents
R1
HAWKI Calibration Plan
R2
HAWKI User Manual
R3
HAWKI Template Reference Guide
R4
GRAAL Commissioning Plan
R5
AOF and HAWKI Commissioning
R6
HAWKI Closeout Calibration Plan
Siebenmorgen et al.,
VLT-PLA-ESO-14800-3214
Carraro et al.,
VLT-MAN-ESO-14800-4076_v92
Siebenmorgen et al.,
VLT-SPE-ESO-22000-5949
Paufique et al.,
VLT-PLA-ESO-14850-4889
Siebenmorgen,
VLT-PLA-ESO-22200-4891
Siebenmorgen et al.,
VLT-PLA-ESO-14800-6011
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1.3 List of Abbreviations & Acronyms
This document employs several abbreviations and acronyms to refer concisely to an
item, after it has been introduced. The following list is aimed to help the reader in
recalling the extended meaning of each short expression:
2MASS
Two Micron All Sky Survey
AO
Adaptive Optics
AOF
Adaptive Optics Facility
ETC
Exposure Time Calculator
FoV
Fiedl of View
GRAAL
Ground Layer adaptive optics assisted by Lasers
FWHM
Full Width at Half Maximum
DIT
Detector Integration Time
HAWKI
High Acuity Wide-filed K-band Imager
NDIT
Number of Detector Integration Time
OB
Observing Block
OS
Observation Software
OT
Observation Template
P2PP
Phase 2 Proposal Preparation Tool
S/N
Signal-to-noise ratio
TBC
To Be Clarified
TBD
To Be Defined
TSF
Template Signature File
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Introduction
In the following we give some basic introduction to the HAWKI instrument and
GRAAL. Readers that are knowledgeable in the HAWKI and AOF project can skip
this section.
2.1 Instrument overview
HAWKI is a wide-field (7.5' x 7.5'), NIR (0.9-2.5μm) camera operating only in direct
imaging mode.
The instrument is cryogenic (120 K, detectors at 75 K) and has a full reflective
design.
The light passes four mirrors and two _filter wheels before hitting a mosaic of four
Hawaii 2RG 2048 x 2048 pixels detectors. The F-ratio is F/4.36 (1” on the sky
correspond to 169.4μm).
In the field of view one shall notice the small cross-shaped gap of ~15’’ between the
four detectors). The pixel scale is 0.106’’/pix . The two filter wheels of six positions
each host ten filters: Y, J, H, Ks (identical to the VISTA filters), as well as 6 narrow
band filters (Br α, CH4, H2 and four cosmological filters at 0.984, 1.061, 1.187, and
2.090μm).
Typical limiting magnitudes (S/N=5 in 3600s on source) are around J= 23.9, H= 22.5
and Ks= 22.3 mag (Vega).
For a detailed description see HAWKI User Manual (RD-2). For a complete
description of science exposures the user have to specify ETC input parameters as
detailed at: http://www.eso.org/observing/etc/doc/helphawki.html#version
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Figure 1: HAWKI as a CAD drawing attached to the VLT and as built in the
integration hall in Garching.
2.2 HAWKI combined with GRAAL
The ground layer adaptive optics system assisted by lasers (GRAAL) is a wave-front
sensor module of the AOF, that is designed to provide ground layer adaptive optics
(GLAO) for the HAWKI NIR wide field imager (7.5’x7.5’ FoV with ~0.1” pixels).
GRAAL is a module hosting 4 WFSs four LGS and a tip-tilt sensor for an NGS. The
atmospheric turbulence is sampled in 4 slightly different directions around the
instrument field-of-view to send an average correction, homogeneous over the
scientific field-of-view, to the deformable secondary mirror (DSM) of UT4. The
improvement provided by the AOF can be summarized (see RD2) in saying that it
will allow HAWKI to work most of the time under better than median seeing
conditions (e.g. the FWHM of the PSF will be reduced typically from 0.53” to 0.42” in
K). Even under most conditions (1” seeing in the visible), the 50% encircled energy
diameter will be reduced by 12 % in the Y and 21 % in the Ks filter over the entire
field-of-view.
The system will use the DSM “approximately” conjugated to the ground. The DSM
will have enough stroke and degrees of freedom to correct for the atmospheric
seeing (up to 2” seeing) including the atmospheric tip-tilt and for VLT field
stabilization. Four sodium laser guide stars emitted from four 30cm laser projectors
located on the VLT centrepiece will be sensed by four 40×40 wave-front sensors
(WFS). These wave front sensors must rotate to compensate for the pupil rotation at
the Nasmyth focus and have to acquire and track the focus of the corresponding
laser spots. As a baseline, a visible tip-tilt sensor has been considered.
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Observing modes
The are three observing modes:
1) Non-AOF mode
2) AOF TT-star-free mode
3) AOF mode (standard)
The Non-AOF mode covers the currently available observing modes of HAWKI where
only field centre, instrument orientation, target offset and optionally the VLT guide star
position can be defined. This mode is useful when the user is not interested in any AO
correction but rather desires the shortest possible setup times (e.g. bright star
photometry, transient objects).
The AOF TT-star-free mode allows the setup of the instrument when no suitable
GRAAL TT-star is available but some degree of AO correction is still desired and can
be realized via the Laser Guide Star only. For instruments like SINFONI this is
referred to as “seeing enhancer” mode. Here the field centre, instrument orientation,
target offset and optionally the VLT guide star position can be defined. The telescope
is set into AOF-mode and the necessary preparations for AOF support (e.g. laser) are
started.
The AOF mode allows the full setup of the instrument configuration including the
GRAAL TT-star position.
The default observing mode is the AOF mode.
4
Performance Improvement for SCIENCE
HAWKI with GLAO would constantly reach, for the same integration time, 0.3 mag
fainter point sources at same signal-to-noise than without correction.
The AOF will emphasize HAWKI’s strengths: very deep imaging at high spatial
resolution. Note that HAWKI with GLAO will reach the same magnitude limit as
VISTA about 12 times faster. I.e., even with the significantly smaller FoV, HAWKI
with GLAO would reach 1/2 the survey speed of VISTA but with at least a factor of
two improvement on the spatial resolution.
HAWKI prime science cases include deep multi-color surveys at high z, stellar
population studies in nearby galaxies, investigations of star forming regions in our
galaxy. These programs critically rely on the deepest possible exposures with the
highest possible spatial resolution – both of which will be improved by GRAAL.
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HAWKI with GLAO will typically reach 0.3 mag deeper in J, H and K for a fixed
exposure time. For high z observations, this is equivalent to a gain of 1.14 in
distance (adopting a standard cosmology). This translates in turn into ~25% more
volume probed by the survey in the same time (surveys will reach z ~ 1.2 instead of z
= 1 or z ~ 3.6 instead of z~ 3).
For surveys aiming at studying galaxies at fixed redshift, or stellar populations in a
given nearby galaxy, this translates into vastly increased number statistics, as the
galaxy luminosity function increases exponentially and the stellar initial mass rises
with a power > 2 in the regime of interest.
Proposals addressing forefront science often require the best seeing conditions.
Currently, the natural seeing in the K band is better than 0.4” only 20% of the time.
With GLAO, an image quality in the K band below 0.42” will be achieved and so will
provide 4 times more time for the most challenging proposals.
For HAWKI “the AOF shall reduce by 15% in Y and 21% in Ks band the diameter
collecting 50% EE for 1 arcsec seeing over the entire field of view of 7.5x7.5 arcmin”
(see RD1, TLR1) with a goal to produce images which are limited by the instrumental
(detector) sampling providing an equivalent image quality of 0.2 arcsec” (see RD1,
TLR2).
5
The existing HAWKI ETC
The HAWKI ETC is available at:
-
http://www.eso.org/observing/etc
Over the past observing semesters it is found that the present ETC returns good
estimates of the integration time needed in order to achieve a given S/N.
-
The ETC input parameters follow ESO standards. Please see the online
help that provides a fair description of the ETC input parameters.
-
The input magnitude can be specified for a point source, for an extended
source (in which case we compute an integration over the surface defined
by the input diameter), or as surface brightness (in which case we
compute values per pixel e.g. 106 x 106 mas).
-
Results are given as exposure time to achieve a given S/N or vice versa
as S/N achieved in a given exposure time. In both cases, one is requested
to input a typical DIT, which for broad-band filters is typically 10 to 30s and
for narrow band filters as long as 60 and 300s. For the later choice, the sky
background gives the limit.
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There are many graphical output options available, such as for verification
of line emission from the target or the sky. This is of interest when narrowband filters are used.
The screen output from the ETC includes the input parameters together with the
calculated performance estimates. Here some additional notes about the ETC output
values:
-
The integration time is given on source: depending on the technique to
obtain sky measurements (jitter or off-sets), and accounting for overheads,
the total observing time is much larger.
-
The S/N is computed over various areas as a function of the source
geometry (point source, extended source, surface brightness).
We conclude that the present HAWKI ETC covers the non-AOF mode of the
combined HAWKI /GRAAL system. No changes to the existing ETC are foreseen
for such non-AOF observations.
For a detailed description of the parameter that the user needs to enter into the ETC
front page see http://www.eso.org/observing/etc/doc/helpHAWKI.html#version
This help page will be updated with respect to:
a) "Atmosphere" section; the new ETCs will use a new unified convention for
seeing/image quality and use the new Austria in-kind sky background model.
b) The computation of the FWHM when using the AO correction as described in
the following section.
6
Model for AO correction
The image quality improves once the AO correction is in use. No analytical model
has been developed so far for GLAO, that allows a simple implementation in the
ETC. Such a task is complex and would require to use 𝐶𝑛2 - profiles as a function of
seeing and airmass. We looked for a simpler empirical model and scanned the
parameter space seeing, airmass, wavelength. We then derived a simple fitting
model, allowing a robust estimation of GRAAL performance.
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We define
𝜆 −0.25
𝑡𝑚𝑜𝑑 = (0.67 ∙ 𝜎𝐷𝐼𝑀𝑀 + 0.27) ∙ 𝑎𝑚0.5 ∙ (2)
+ 0.2 ∙ 𝜆−2.
where 𝜎𝐷𝐼𝑀𝑀 is the DIMM seeing in arcsec, 𝑎𝑚 and 𝜆 the airmass and wavelength in
µm for the observation.
𝑡𝑚𝑜𝑑 is equivalent to a turbulence, at the wavelength and airmass of observation. The
sensitivity to airmass and wavelength differs from seeing-limited classical formulae
as expected with an adaptive optics system, and an additional wavelength
dependency term has been added to improve the fitting quality.
The GLAO performance with or without a bright or faint TT star, with error budget,
can be written as:
2
FWHMGLAO = √(max(200, 𝐹𝑊𝐻𝑀𝑜𝑝𝑡 ) + 1172 ) ,
2
𝐹𝑊𝐻𝑀𝑓𝑎𝑖𝑛𝑡 = √(max(200,1.03 ∙ 𝐹𝑊𝐻𝑀𝑜𝑝𝑡 ) + 1172 ) ,
2
𝐹𝑊𝐻𝑀𝑛𝑜𝑇𝑇 = √(max(200,1.15 ∙ 𝐹𝑊𝐻𝑀𝑜𝑝𝑡 ) + 1172 ) ,
where
𝐹𝑊𝐻𝑀𝑜𝑝𝑡 = √(1290 ∙ 𝑡𝑚𝑜𝑑 − 560)2 + 1502 − 30
A value of 117 mas has been considered as an equivalent error budget value for the
instrument and GRAAL, with 100 mas from HAWKI PSF and 60 mas from GRAAL.
7
ETC upgrade: Specifications
From the analysis detailed in the Appendix we set up the following requirements for
the ETC upgrade:
R1 Implement the AO model as described in Section 6.
R2 Implement the ETC front page as defined in Figure 2 and Figure 3.
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Figure 2: Design of the HAWKI ETC front page. The input parameters are
described at http://www.eso.org/observing/etc/doc/helpHAWKI.html#version .
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Figure 3: Zoom in the HAWKI ETC front page concerning the choice of the
offered AO modes.
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Appendix
This work is completed and the section written by J. Paufique.
8.1 GRAAL performance estimates: ETC versus Octopus
The ETC formula has been compared against an AO simulator called Octopus.
Octopus results can be modeled with a limited number of parameters for a non-linear
fit of the performance. After a proper match of the atmospheric and instrumental
parameters used for both cases, the agreement is good. The performance of GRAAL
in Octopus is then checked for consistency in terms of image quality improvement.
Formulae for the ETC calculator including GRAAL are provided.
8.2 Octopus simulations
Octopus simulations have been used for GRAAL performance characterization. The
atmosphere has been set to the best estimates we have of it, using data from both
the Paranal ASM and from the UTs (both instrument imaging and Active optics data).
The extensive studies performed on the topic led to a good agreement between
results and atmospheric derived parameters. We therefore consider these as the
baseline to be used for operation.
References:



Martinez, P. et al., On the Difference between Seeing and Image Quality: When
the Turbulence Outer Scale Enters the Game, 2010Msngr.141....5M
Sarazin, M., et al., Seeing is Believing: New Facts about the Evolution of
Seeing on Paranal, 2008Msngr.132...11S
Kolb, J., Input parameters for the AO facility simulations, VLT-SPE-ESO11250-4110, ESO-048940
8.3 Exposure time calculator
The ESO exposure time calculator (ETC) provides an estimate for the FWHM of an
image delivered by a Unit telescope.
The variable used by the ETC are:
- DIMM seeing (at 500 nm)
-
Airmass of observation
-
Observation wavelength
Besides, it uses the following internal parameters values:
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parameter
Value for the original ETC
DIMMto
UT-seeing
formula (at 500 nm)
Outer scale
Telescope FWHM
Instrument FWHM
σUT = (σDIMM+0.25)/1.5
Value for Octopus and the
recommended
HAWKI
facility ETC (no AO mode)
σUT = 0.71·σDIMM + 0.225
90 m
30 mas
200 mas
23 m
30 mas
200 mas
In the following, the ETC is used exclusively with the recommended values listed in
the table above.
Open-loop comparison:
Adding to the Octopus results the FWHM as for the ETC leads to a reasonable
agreement between simulations and ETC, especially for good and median seeing
with less than 100 mas difference between them, as illustrated on Figure 1. Octopus
results are in this figure including the same error budget as listed in the ETC
(200 mas FWHM for the instrument, 30 mas for the telescope). In this case, the ETC
marginally underestimates the actual PSF at short wavelength, whereas it provides a
somewhat conservative estimate at longer wavelengths.
Figure 4: Example of a comparison case between ETC and Octopus. DIMMseeing of 0.6 arcsec, airmass of 1.3.
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The following table shows the discrepancy in image quality between ETC model and
Octopus simulation results. A positive value corresponds to the ETC overestimating
the PSF FWHM, where this ETC used provides a conservative estimate of the
instrument performance.
The small discrepancies seen for good seeing cases are probably related to the
short Octopus simulation duration, which prevents the tip-tilt from being fully
developed on the PSF in our simulations. Besides, active optics guiding is taken into
account neither in the ETC nor in Octopus simulations, such that results real-life
performances will outperform ETC results.
Discrepancies for larger values of seeing are not fully understood as of today. They
might be linked for instance to corrective factors used within the ETC to optimize the
atmosphere fitting, not meant for fitting large seeing results. Such factors are not
used in Octopus, where the image formation follows a statistical realization of
atmospheric phase screens.
Airmass seeing Min-max
discrepancies (mas)
1.3
0.6
-20/+30
2
0.8
+5/+30
1.3
0.8
+20/+55
1.3
0.4
-5/+70
1.3
1.2
+130/+110
1.3
1.8
+190/+140
1
1.8
+160/+125
Table 1: result comparison (ETC FWHM - Octopus FWHM). A positive value
means that the ETC provides a larger PSF than Octopus simulation, i.e. a
conservative performance estimate.
8.4 Use cases for AO correction
A comparison has been made with these figures, showing the performance of the
system in different cases.
With the exception of very poor seeing, the estimator performs conservatively.
Especially, GLAO operation is always more than 10% conservative for the seeing
cases 0.4”-0.8”: most difficult programs ETC estimations provide a conservative
evaluation of GRAAL’s performance, minimizing the risks of not reaching the
expected performance.
It should be also noted that in one case, the NoTT model performs marginally worse
than the noAO case (case of 0.8”seeing, airmass 2, wavelength of 0.98µm).
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Such non-physical cases should be addressed in the ETC, such that in case the
FWHM in an AO mode exceeds the noAo mode, it should be replaced by the noAO
value.
seeing Airma
ss
1.8
1.3
Wav
elengt
h
(µm)
0.98
GLAO
GLAO
model
(mas)
1.8
0.8
0.4
0.4
0.8
0.8
1.8
1.3
1.3
1.3
1.3
2
2
2
2.16
2.16
2.16
0.98
2.16
0.98
2.16
1.8
2
0.98
1693
1561
0.8
0.8
1.3
2
1.6
1.6
325 / 382
503 / 586
/ Faint
faint
model
(mas)
1235
/
1151
888 / 779
270 / 315
131 / 232
200 / 300
417 / 495
686 / 776
1280
/
1096
/ noTT
noTT
model
(mas)
1241
/
1185
893 / 802
277 / 323
137 / 232
207 / 307
425 / 509
700 / 799
1286
/
1128
/ 1695
1607
332 / 393
517 / 603
/ Ref:
ETC
noAO
1243
/
1321
897 / 894
283 / 356
213 / 232
345 / 338
427 / 565
694 / 890
1287
/
1258
/ 1696
1793
335 / 434
512 / 671
Table 2: comparison Octopus results / model.
Gain GLAO
model
/
noAO
1509
0.76
1156
489
282
353
644
852
1545
0.67
0.65
0.74
0.8
0.75
0.90
0.71
/ 1991
0.78
550
722
0.69
0.81
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8.5 Further comparisons of AO performance estimates.
Octopus full result list is given below.
GLAO:
lambda
airmass
seeing
2.16
2.16
2.16
2.16
2.16
2.16
2.16
2.16
2.16
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
2
2
2
1.3
1.3
1.3
1
1
1
2
2
2
1.3
1.3
1.3
1
1
1
2
2
2
1.3
1.3
1.3
1
1
1
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
fwhm
Oct
175
413
1280
117
264
885
94
203
700
210
503
1434
135
325
1018
106
250
819
308
683
1693
191
457
1234
148
361
1015
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HAWKI/GRAAL
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TT faint:
lambda
2.16
2.16
2.16
2.16
2.16
2.16
2.16
2.16
2.16
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
airmass
2
2
2
1.3
1.3
1.3
1
1
1
2
2
2
1.3
1.3
1.3
1
1
1
2
2
2
1.3
1.3
1.3
1
1
1
seeing
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
fwhm
183
421
1286
123
270
891
100
209
704
216
517
1439
141
332
1024
112
256
826
321
697
1695
198
471
1240
153
373
1019
Doc:
Issue
Date
Page
VLT-SPE-ESO-22200-6100
1
27.01.15
19 of 22
HAWKI/GRAAL
Exposure Time Calculator
No TT:
lambda
2.16
2.16
2.16
2.16
2.16
2.16
2.16
2.16
2.16
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
0.98
2.16
2.16
2.16
1.6
1.6
1.6
0.98
0.98
0.98
2.16
2.16
2.16
airmass
2
2
2
1.3
1.3
1.3
1
1
1
2
2
2
1.3
1.3
1.3
1
1
1
2
2
2
1.3
1.3
1.3
1
1
1
1
1.3
2
1
1.3
2
1
1.3
2
1
1.3
2
seeing
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.4
0.8
1.8
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
1.2
1.2
1.2
fwhm
300
423
1287
204
277
895
159
222
711
368
512
1442
254
335
1028
199
261
828
474
691
1696
340
465
1242
276
370
1022
152
192
284
175
226
348
248
321
507
412
538
796
Doc:
Issue
Date
Page
VLT-SPE-ESO-22200-6100
1
27.01.15
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HAWKI/GRAAL
Exposure Time Calculator
1.6
1.6
1.6
0.98
0.98
0.98
1
1.3
2
1
1.3
2
1.2
1.2
1.2
1.2
1.2
1.2
499
629
907
638
782
1086
airmass
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
seeing
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
1.2
1.2
1.2
1.2
1.2
1.2
fwhm
315.408
211.893
165.873
384.637
267.296
211.057
490.287
357.076
291.539
490.864
337.548
266.369
577.492
408.19
333.208
700.413
521.304
434.594
615.945
431.823
351.454
704.36
510.324
420.66
842.973
628.247
525.006
865.643
636.105
525.989
968.236
717.182
596.328
No AO:
lambda
2.16
2.16
2.16
1.6
1.6
1.6
0.98
0.98
0.98
2.16
2.16
2.16
1.6
1.6
1.6
0.98
0.98
0.98
2.16
2.16
2.16
1.6
1.6
1.6
0.98
0.98
0.98
2.16
2.16
2.16
1.6
1.6
1.6
Doc:
Issue
Date
Page
VLT-SPE-ESO-22200-6100
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HAWKI/GRAAL
Exposure Time Calculator
0.98
0.98
0.98
2.16
2.16
2.16
1.6
1.6
1.6
0.98
0.98
0.98
2
1.3
1
2
1.3
1
2
1.3
1
2
1.3
1
1.2
1.2
1.2
1.8
1.8
1.8
1.8
1.8
1.8
1.8
1.8
1.8
1133.44
851.232
714.081
1372.84
1017.38
846.662
1513.27
1130.94
947.586
1750.87
1318.59
1111.72
Doc:
Issue
Date
Page
VLT-SPE-ESO-22200-6100
1
27.01.15
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