Troubleshooting guide

V.Taking Spectra with FLAMINGOS

A. Overview

FLAMINGOS may be used for obtaining long slit spectra at the 2.1-m; please see § I. FLAMINGOS + KPNO

2.1-m Overview for resolving powers within selected passbands. Multiobject spectroscopy is currently

supported only at the 4-m telescope. As with imaging, the sky emission is variable and bright, and there is

additional background in the HK mode from the camera dewar window. It is necessary to subtract this

contribution from the target spectrum. This is accomplished by dithering the target up and down the slit. Two

possible techniques are walking up the slit at 5 to 7 different locations, and nodding the telescope back and forth

between two offset positions, A and B, in an ABBA pattern, symmetrically placed about the target's initial

alignment position. Dithering in an ABBA pattern can be done by hand, or automatically with a script.

Walking up or down the slit must be done by hand.

Telescope guiding is required, as the integration times are generally long, and the time to align a long slit or

MOS plate is also significant. The guide camera is an intensified CCD attached to an extension to the

instrument mounting adapter on the North side of FLAMINGOS. It is fed by a folding mirror mounted at the

periphery of the MOS dewar vacuum window. Consequently, the guider field of view is about 160" East and

1500" South of the FLAMINGOS pointing center

. The guider plate scale is ~0.53" pixel

-1

, and the field of

view is about 5.6' in RA × 4.2' in Dec.

The default bias for spectroscopy is 0.75 V, where the array has lower dark current than at the imaging bias of

1.0 V. The current bias value may be obtained by hitting the Update All Items button on the UFSTATUS GUI.

NOTE: the MCE4 array controller automatically sets the bias to 0.776 V on boot, which is not a bias voltage

used in any configuration. The initialization script initflam.pl sets the bias to 1.0 V, and then queries whether

you wish to change the bias. If MCE4 crashes and you have to run initflam.pl, don't forget to reset the bias for

spectroscopy!

The detailed procedures for aligning a long slit appear in the sections immediately following. Operation of the

guider is included in these instructions; references to the relevant figures from the manual FLAMINGOS at the

KPNO 2.1-m: Telescope Console Control Panels and GUIs used for Guiding (hereafter, Guiding GUIs) are

included as an additional aid towards understanding the alignment procedure.

There are two types of slits which may be used for spectroscopy. There are a number of fixed long slits

installed in the MOS wheel, in between the MOS mask locations, with widths of 2, 3, 6, 8, 12, and 20 pixels.

Because of their proximity to the MOS masks, these must be used with the Decker wheel set to the slit position,

and it is necessary to carefully set up the Decker wheel to ensure that the narrow aperture does not vignette the

slit. There are also a number of custom slits which have been machined in MOS masks and can be used with

the much wider MOS decker, which can greatly facilitate acquisition of the target.

Commonly used slits in MOS masks are:

UF 3pix This is a single long slit 3 × 1680 pixels (1.81 × 1020 arcsec at 2.1-m)

NOAO 2 pix The three NOAO slits are 2, 3, 4 pixels (1.21, 1.81, 2.42 arcsec) wide and

NOAO 3 pix consist of two slits each 120 arcsec long centered 120 arcsec on either side

NOAO 4 pix of a 20 arcsec square aperture which is used for acquisition

Unless the long slit length is required for science, the NOAO slit masks are more suitable for compact source

spectroscopy because the acquisition aperture greatly simplifies centering the target on the slit.

6 These may change each time the instrument is mounted onto the telescope, but should be somewhat close to these values.

FLAMINGOS@2.1-m, Ver. 2.39, 2011 May 13 Page 24 of 46