NOAO Extremely Wide-Field Infrared Imager


Filters Overview

Just the facts, quick!
NEWFIRM Quick Guide for Proposal Preparation
Darks, flatfields, and on-sky images
NEWFIRM Use Policies
NEWFIRM Filter Availability and Policy on Filter Changes
NEWFIRM Scheduling Policy through 2011
The NEWFIRM Instrument
NEWFIRM System Overview
NEWFIRM Optical Design
SDN 1101 Imaging Performance Requirements
SDN 2201 NEWFIRM Warm Lens Optical Prescriptions
SDN 2202 Physical Dimentions of Warm Optics Layout
Optics section of PDR document
NEWFIRM Filter Overview
NEWFIRM Filter Availability and Policy on Filter Changes
NEWFIRM Filter Identification and Properties List
Filter data packs
1056 nm data pack
1060 blocker data pack
1063 nm data pack
1187 nm data pack
1644 blocker data pack
1644 nm data pack
2096 nm data pack
2124-68 blocker data pack
2124 nm data pack
2168 nm data pack
H 127 77K data pack
H+K blocker data pack
HX data pack
J blocker data pack
JX data pack
KX data pack
Lists of Installed Filters
2008B first half
2008B second half
NEWFIRM InSb Array Detectors
ORION SCA Laboratory Test Results Summary
Photon Transfer Curve Reports
Linearity Tests and Characterization
2K x 2K InSb for Astronomy (SPIE 2004)
Observing with NEWFIRM
Infrared Observing Methods Primer
NOCS Starup, Data Taking, and Error Recovery Procedures
Guide to Observing Protocols
NOCS Script Generator Tool
Operation of the NEWFIRM Guider
Data Reduction
NEWFIRM Data Reduction Pipline Handbook
NEWFIRM Technical Publications
2K x 2K InSb for Astronomy (SPIE 2004)

Ron Probst, NEWFIRM Instrument Scientist

August 2008

This overview presents general properties of NEWFIRM's filter set, with pointers to technical details, use history, and policies for filter access and scheduling.

The NEWFIRM camera uses cryogenic filters 124 mm in diameter x 5 mm thick.  These are located in two, 8-position filter wheels very close to the cold pupil image and Lyot stop.  Although NEWFIRM's scientific range is 1-2.4 microns, its InSb arrays in combination with its lens materials and coatings are sensitive out to 3.8 microns.  Thus longwave blocking is necessary. For some filters this is provided by using two pieces of glass, one defining the bandpass and one providing the blocking, with a piece in each filter wheel.  This impacts the total suite of wavelength-defining filter options that can be offered at any one time.  Changing filters is time consuming and impacts instrument availability on-sky.  The broadband J, H, and KS set is permanently installed; installation of other filters is dependent upon scientific merit, scheduling constraints, and technical issues and is at the NOAO Director's discretion.

The optical beam originating from any image point in the input focal plane is collimated at the filter (≈ pupil) location.  However the angle of incidence of this collimated beam changes with its point of origin in the focal plane.  The beam originating from field-of-view center passes through the filters at normal incidence.   Maximum beam tilt is 13.5 degrees for image points at the corners of the field of view.  The optical result is that the filter bandpass is increasingly blueshifted from center to corner of the field of view.  This is negligible for the broadband filters but significant for narrowband (R > 75) filters.  The Galactic emission line filters ( [Fe II] 1.64 mm, H2 2.12 mm, Br g 2.17 mm) are designed to capture the line of interest somewhere within the effective filter bandpass for all points in the field of view, as this bandpass shifts across the line with changing field position.

The NEWFIRM Filter Identification and Properties List compiles identifications and basic bandpass properties for all NEWFIRM filters in NOAO's possession.  This includes PI-provided filters requiring permission for use.  Filter data packs provided under this heading have transmission curves and other technical details for each piece of glass.  Bandpass defining filters and out-of-band blockers are treated separately.

Lists of NEWFIRM filters for [semester] identify what has been installed in the Dewar at various times.  These provide a guide--but not a guarantee--to combinations that may be installed in the future.

NEWFIRM Filter Availability and Policy on Filter Changes presents Observatory policies governing filters available to all users and those for which owner permission must be obtained prior to proposal submission.

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NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation.

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