SOFI

Instrument Evolution

This page contains information about the time evolution of various instrumental parameters, such as the RON, the number of bad pixles, the gain, the throughput. If you have data that can be relevant to these issues please e-mail them to us, it will help us to monitor the instrument performance.

Detector Characteristics
Instrument Throughput, Atmospheric Extinction and Filter Transformations
Focus Pyramid
Collimator Focus Positions
Encoder Positions

Detector Characteristics:

Read-out Noise : Last values (Unit : ADU)

Date \ Qaudrant	Lower Left	Lower Right	Upper Left	Upper Right
Nov 16 2002	2.439	2.094	2.097	2.131

Read-out Noise evolution since January 1998

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Gain : Last value (Unit : e-/ADU)

Date	Gain
Nov 22 2002	5.267

Gain evolution since August 1998

Non-Linearity

Month	Gain
Nov 2002	Less than 1.5% between 50 and 10000 ADUs

Bad pixels

Last values :

Date	Dead pixels	Hot pixels	Noisy pixels	Total bad pixels
Nov 1999	170	1406	negligeable	1580

go to the bad pixel image

Instrument Throughput, Atmospheric Extinction and Filter TransformationImaging Modes

Zero Points

Imaging mode and filter J - LF H - LF Ks - LF Z - LF J - SF H - SF Ks - SF J - SO H - SO Ks - SO Ks - HRF J - LF_FE Ks - LF_FE

Zero Point 22.97 22.86 22.31 22.60 23.34 23.03 22.50 22.94 22.86 22.34 22.32 23.14 22.38

Date of last measure Feb 2002 Feb 2002 Feb 2002 Dec 1997 May 1998 May 1998 May 1998 Jan 2002 Jan 2002 Jan 2002 Dec 1997 Jul 1998 Jul 1998

Zero Point evolution in J, H and K bands, since December 1997

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Atmospheric Extinction

Date \ Filter J H K Ks

La Silla Folklore 0.08 0.06 0.11

October 98 0.10 0.04 0.05

March 00 0.08 0.03 0.05

Filter Transformations
In the following, lower case refer to SOFI instrumental magnitudes' corrected for atmospheric extinction and upper case letters refer to tabulated magnitudes in the Persson et al. list of standards. Stars in the J-Ks colour range 0.24 to 1.28 were used to derive the following relationships.

J-j=-0.007(J-K)+23.15, fit residual 0.013 magnitudes

H-h=-0.022(J-K)+22.98, fit residual 0.009 magnitudes

Ks-ks=0.023(J-K)+22.38, fit residual 0.013 magnitudes

K-ks=-0.005(J-K)+22.39, fit residual 0.017 magnitudes

These results are preliminary and a more detailed analysis, including errors, will be listed soon.
Spectroscopic Modes

Counts are in electrons per second per Angstrom for a 15th magnitude A0 star at Zenith.

Date \ Grism-Wavelength Blue 10500 Blue 12000 Blue 13000 Blue 15000 Red 16000 Red 17000 Red 22000 Red 23000 Red 24000

March 1998 4.5 3.8 2.9 1.9 1.7 1.6 1.1 0.83 0.61

Focus Pyramid

The distance "d" between the four outlying images produced by the focus wedge and the central image and the telscope defocus "f" are linearly related by d=a+b*f. Errors in the co-efficients are in brackets.

Date\Co-efficients	a	b
December 1997	35.2	-15.4
March 1998	35.1	-14.4
May 1998	35.1	-16.4
July 1998	34.95 (0.12)	-15.5 (0.5)
August 1998	35.21 (0.09)	-16.8 (0.4)
September 1998	35.11 (0.11)	-14.9 (0.4)
January 1999	35.05 (0.10)	-14.9 (0.3)

Collimator Focus

Imaging mode	Date of last test	Ks	H	J	Z	NB_1.061	NB_1.187	NB_2.090	NB_2.195	NB_HeI_J	NB_1.215	NB_FeII_J	NB_Pbeta	NB_FeII_H	NB_1.71	NB_HeI_K	NB_H2_S1	NB_Brgamma	NB_CO	NB_2.248	NB_2.28
Large_field_imaging	15Apr2000	2944	3293	1849	404	2436	3796	4708	4543	2826	3787	4914	4979	11793	5989	5168	7552	5216	4841	7411	5046
Small_field_imaging	22Jan2000	-2651	-2852	-4733	-1354	-1793	-1902	-1930	-2246	-1740	-1834	-486	-896	1788	-371	-1461	-1121	-1243	-1538	132	-1704
Spectroscopic_Objective	23Jan2000	2537	-295	-2596	-6254	-3190	-1482	2553	2813	-3021	-1098	-129	186	5562	2227	2580	3105	2661	2630	3892	1969

Grisms

The optimal focus for the grisms is determined by using the JG mask. I.e., the focus is determined for the best spatial resolution. In general, the position of the collimator required to obtain the best spectral resolution is different from the collimator position required for the best spatial resolution.

Date\Grism	Blue Grism	Red Grism	HR Z	HR J	HR H	HR Ks
980517	2000	0
990122	-1567	541	1294	2016	3924	5607

Wollaston

Date\Filter	Wollaston Lower (Ks)	Wollaston Upper (Ks)
980630	3883	2976

Encoder Positions

See the relavent SPC file on wsofi.

Send comments to Leonardo Vanzi <lvanzi@eso.org>
Last update: October 2, 1999

Date \ Filter	J	H	K	Ks
La Silla Folklore	0.08	0.06	0.11
October 98	0.10	0.04		0.05
March 00	0.08	0.03		0.05

Date \ Grism-Wavelength	Blue 10500	Blue 12000	Blue 13000	Blue 15000	Red 16000	Red 17000	Red 22000	Red 23000	Red 24000
March 1998	4.5	3.8	2.9	1.9	1.7	1.6	1.1	0.83	0.61