EUROPEAN SOUTHERN OBSERVATORY

La Silla Observatory

SCIENCE OPERATION DEPARTMENT

SciOps Technical Report:
NTT, Aug.2004
SuSI-2 Baffling Status
LSO-TRE-ESO-40200-1105/1.0

Prepared

Olivier Hainaut

2004-08-23

Revision History

0.1	2004-08-22 creation ohainaut
1.0	2004-08-23 released, ohainaut

1.- INTRODUCTION

1.1 SUMMARY

PinHole images obtained with SuSI-2, together with a cardboard baffle at the entrance of the Nasmyth tunel, are analyzed, confirming that the baffling is defficient. The images are compared with those obtained last year without the baffling, cf [1].

A study of the stability of the SuSI-2 flatfield with rotator position was performed, indicating a strong light excess in a direction correlated with the position of the rotator. This study, available in [2], suggested a problem with the baffling of the instrument. In the framework of a general improvement of the baffles of the La Silla Telescopes by LED/OPT, lead by A.Gilliotte, pinhole tests were performed SuSI2.

1.2- STYLISTIC CONVENTION

1.3- ACRONYMS AND DEFINITIONS

SciOp: La Silla Science Operation Department
LED: La Silla Engineering Department
SuSI2: Superb Seeing Imager on the NTT
NTT: New Technology Telecope

1.4- DOCUMENTS AND REFERENCES

[1] LSO-TRE-ESO-40200-1061, SuSI-2 Baffling Status, ohainaut.
[2] LSO-TRE-ESO-40200-1053, 28 Jan - 2 Feb 2002 Technical Time: Technical Report, O.Hainaut

2.- Data

Pinhole images (i.e. mounting a plate with a pinhole in the filter wheel) were obtained on April 27, 2003. The telescope was pointing to the FlatField screen. These images were described and analyzed in [1].

On Aug.22, 2004, more images were obtained using the same pinhole, but this time with an additional black paper baffle installed at the entrance of the Nasmyth tunel.

<>The baffle is a annulus filling the entrance of the tunel (taped on the shutter), with a clear aperture of 26cm diam centered on the axis of the tunel. The frames are
SUSI2.2004-08-22T21:29:50.62.fits
SUSI2.2004-08-22T21:30:23.56.fits
<>SUSI2.2004-08-22T21:30:56.21.fits
<>SUSI2.2004-08-22T21:31:28.84.fits

Figure 1 displays the pinhole image without the cardboard baffle (2003 data), Fig 2 with the baffle. Figure 3 shows the image of Fig.1 with some label. Note that some of the labels in the similar figure of [1] were wrong.

Figure 1: pinhole image obtained without the baffle

Figure 2: pinhole image obtained with the baffle

Figure 3: Image of Fig.1 with some labels.

3. Measurements.

Table 1 lists the counts from the M1 mirror (i.e. the light we want) and the contamination (measured as all the flux in the rectangular adaptor window minus the light from M1).

	M1	Adaptor minus M1	Contamination
Without baffle (from [1])	2.50E9	1.22E9	48%
With baffle	2.86E9	1.03E9	36%

Table1: Flux and contamination measurements, with and without baffle.

Figures 1 and 2 and Table 1 show a dramatic improvement in the structure around the optics, but also shows that the reflections on the sides of the Nasmyth tunel are still very important, shows clearly that the tunel should be modified.

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