NEWFIRM Filters

Currently Installed Filters

Filter Availability and Change Policy

There exist more NEWFIRM-specific filters than can be accommodated in the Dewar at one time.  NEWFIRM has two filter wheels, each with 7 slots for filters.  Some of the filters must be used with a blocking filter (i.e., two slots must be used). It takes a minimum of five weeks to change filters (instrument warm-up, change filters, cool-down).  The availability of filters in any given semester will depend on decisions that only can be made after the TAC meets and has provided it raked list of programs.

Changing filters is a time-consuming procedure that removes NEWFIRM from service and does result in some risk to the filters and instrument. Hence, decisions on the filter complement involve balancing scientific rankings of individual proposals, the overall scientific output achievable in any semester, other scheduling concerns, and the health of the instrument.

Filter Identification and Properties List

• This list compiles identifications and basic bandpass properties for all filters produced for NEWFIRM and in our possession.  Prior to recommissioning NEWFIRM on the CTIO 4-m Blanco telescope, some filters required permission of the filters' owners for use by general observers.  As of recommissioning, all NEWFIRM filters can be used by NEWFIRM observers without permission from their owners.  The owners request that general observers using these filters cite their work (details below).
• The term "filter" here means a single piece of glass.  NEWFIRM science bandpasses often require two pieces of stacked glass in series, one in each filter wheel.  One piece defines the bandpass and the second provides longwave out-of-band blocking for the InSb arrays.  Definition of these combinations, and the complement of filters used in NEWFIRM at various times can be found in separate documents.
• Serial numbers: each piece of glass is assigned a unique four digit number according to the following scheme:
  • Filter number XYab
    • X designates the band from 1 to 4
    1. 1 micron band window, shortward of the J window
    2. J window, 1.2-1.4 microns
    3. H window, 1.5-1.8 microns
    4. K window, 2.0-2.4 microns
    • Y designates the spectral resolution R = (λ₀ / Δλ)
    1. broadband, 4 < R < 10
    2. intermediate band, 10 < R < 50
    3. narrow band, 50 < R < 100
    4. ultranarrow band, R > 100
    • ab together are a running number from 01 to 99, generally assigned according to the order of delivery of the filters from vendors. 
• The resolution and order-of-receipt criteria are not strictly applied, in order to group together bandpass-defining filters and out-of-band blockers that form natural sets.
• Filter names: these are logical and convenient identifiers used in the filter wheel GUI.  Alternative names used previously at various times are given for completeness, but future use of these alternatives is discouraged.

* These filters have never been used in NEWFIRM.
¹ There are no restrictions for community use of these filters. If used, please (a) send a brief email to the owners, James Rhoads (james.e.rhoadsATnasa.gov) and Sangeeta Malhotra (Sangeeta.MalhotraATasu.edu) describing the project and (b) cite Coughlin et al. 2018, ApJ, 858, 96 in your publications.
² There are no restrictions for community use of these filters. If used, please cite van Dokkum, P.G, et al. 2009, PASP, 121, 2
in your publications
³ There are no restrictions for community use of these filters.