MOSAIC Filters

The Mosaic II imager, used at the Blanco 4-m prime focus, takes filters that are 146x146 mm and 12 mm (nominal) thick. A set of standardized filter names and IDs for both Mosaic I on the KPNO Mayall and Mosaic II on the CTIO Blanco have been developed to ensure proper application of astrometric solutions and real-time display processing (as well as future archive uniformity). These official names are listed in the Mosaic filter list web page.

Focus offsets are referred to the R filter, since this is the filter we use for taking focus frames each night when the Mosaic is installed in order to monitor telescope performance.
Note that the Sloan set (griz) and the Johnson-Cousins BVR (but not I) sets should be near-identical to those at KPNO, see the KPNO Mosaic Filters.

Note: The central wavelength of narrow band filters (actually all filters, but it is very significant for narrow band filters) is shifted  approx. 15A to the BLUE in the f/2.87 beam of the Blanco 4m + PFADC corrector as compared to the transmission measured in parallel light. The central wavelengths quoated below are nominally for when the filters used at PF, with the approx. 15A shift included. Furthermore, the filter transmission curves presented below show the simulated filter tranmission curve for the Blanco 4m + PFADC f/2.87 beam.

Note: The Blanco prime focus corrector has poor response in the UV: 90% (4000A), 85% (3800A), 74% (3650A), 54% (3500A), 31% (3400A), 11% (3350A), 0% (3300A). These are calculations from the glass types and AR coating specifications, and the figures for 3300-3400A are rather uncertain. YOU STRONGLY ENCOURAGED TO USE THE u(SDSS) filter rather than the U filter. Neither of these filters, in combination with the CCDs and optical corrector, match the standard passbands perfectly. The U filter uses a (troublesome!) copper sulphate solution as red blocker, whereas the SDSS u filter is an interference filter.

 

Filter Central
Wavelength
(A)		 FMHM
(A)		 Focus
Offset
(um)		 Status NOAO
Code		   
Transmission Curves
Plot Data File
U 3570 650 -185 Ok c6001 .jpg   .ps . txt
B 4360 990  +10 OK c6002 .jpg   .ps . txt
V 5370 940  -30 From 21 Oct 2000 c6026 .jpg   .ps . txt
R 6440 1510  0 Ok; filter offset ref c6004 .jpg   .ps .txt
I 8050 1500  +10 from 24 May 2003 c6028 .jpg   .ps .txt
VR Stubbs
(aka VR Supermacho)		 6100 2000  0 Ok c6027 .jpg   .ps
old.jpg		 .txt
 
C (Wash) 3850 1075  +260 from 05 Jan 2011 c6029 .jpg   .pdf  
M (Wash) 5115 1375  +260  Ok c6007 .jpg   .ps .txt
D51 (DDO) 5130 154  -55  Ok c6008 .jpg   .ps .txt
 
[OII] 3727 50  ?   c6012 .jpg   .ps .txt
[OIII] 4990 50  +130  Ok c6014 .jpg   .ps .txt
Halpha 6563 80  +65  cwl, FWHM nominal c6009 .jpg   .ps .txt
Halpha+80 6650 80  -35  cwl, FWHM nominal c6011 .jpg   .ps .txt
[SII] 6725 80  +60  cwl, FWHM nominal c6013 .jpg   .ps .txt
 
u (SDSS) 3600 400  +230 cwl, FWHM approx,
replacement for c6021,
NO RED LEAK		 c6022 .jpg   .ps .txt
g (SDSS) 4813 1537  +30 "set #2" (in use 8/2000-) c6017 .jpg   .ps .txt
r (SDSS) 6287 1468  +120 "set #2" (in use 8/2000-) c6018 .jpg   .ps .txt
i (SDSS) 7732 1548  -20 "set #2" (in use 8/2000-) c6019 .jpg   .ps .txt
z (SDSS) 9400 2000  -15 Ok c6020 .jpg   .ps .txt
 
 Bj (Tyson) 4350 1650  ? #3, on loan from A. Tyson c6024 .jpg   .ps .txt
 I (Tyson) 8800 2000  ?  cwl, FWHM approx c6025 .jpg   .ps .txt
               
White 6500 5000   Fused Silica c6016    

 

 

Retired Fillters

Filter Central
Wavelength
(A)		 FMHM
(A)		 Focus
Offset
(um)		 Status NOAO
Code		 Transmission Curves
Plot Data File
g (SDSS) 4825 1380 ? "Set #3", red cut-off
a bit too red
(in use < 8/2000)		 c6015    
C (Wash) 3850 1075 +260  some fine scratches
on the anti reflection coating		 c6006 .jpg   .ps .txt
V 5370 940 115 #1 broken... c6003 .jpg   .ps .txt
Bj 4350 1650 ? #2 broken... --    
Bj 4350 1650 ? Filter damaged Nov 2002
Area covered by CCD-1
(SW corner) unusable.		 --    
Old I 8050 1500 +25   c6005 .jpg   .ps .txt

 

 

Last updated: 2009 Dec 9, ARW

 

Staff Contacts:
Sean Points: spointsATctio.noao.edu
Alistair Walker: awalkerATctio.noao.edu