TRISPEC Filters

The instrument has three filter wheels for optical channels, two filter wheels for the each infrared channels in the dewar. Currently, four optical board bandpass filters recommended by Bessell (1990), and five infrared broad bandpass filters by the Mauna Kea consortium (See also specification page by A. T. Tokunaga) are installed. And, the order cut filters for the spectroscopic modes are also installed. The available filters are the below table. On the IR1 channel, a BK7 glass is also permanently mounted as a thermal blocking filter. And, on the slit viewer, a R-65 filter is permanently mounted.

IMPORTANT: The transmission curves of the optical filters (glass filters) are somewhat shifted to shorter wavelength (a few ten nanometers), since the optical filters are cooled down to a temparature of 80K similar to the infrared filters. And, the B and I bandpass filters are truncated at the blue end or the red end by the internal first dichroic.Therefore, the colors of these filters are somewhat differ from the colors described by Bessell (1990). If you wish to do high-precision photometry, you should take time to acquire sufficient calibration observations.


Optical Channel

11th August 2000
Slot Wheel 2 Wheel 4 Wheel 5
Fliter 50%
Cut
On
50%
Cut
Off
Filter 50%
Cut
On
50%
Cut
Off
Filter 50%
Cut
On
50%
Cut
Off
1 open - - open - - open - -
2 B 0.38 0.48 B (*) 0.38 0.48 GG455 0.43 -
3 V 0.475 0.58 V (*) 0.475 0.58 GG495 0.475 -
4 R 0.545 0.68 R (*) 0.545 0.68 (none) - -
5 I 0.71 1.02 I (*) 0.71 1.02 (none) - -
6 close - - prism - - (none) - -

(*) These filter have no AR coating, and aren't glued.
Note: B= 2GG385 + 1BG12 + 2BG39, V=2GG495 + 3BG39, R=2OG570 + 3KG3, I=3RG9 (Bessell 1990)


Shorter Infrared (IR1) Channel

11th  August 2000
Slot Wheel 7 Wheel 8
Fliter 50%
Cut
On
50%
Cut
Off
Filter 50%
Cut
On
50%
Cut
Off
1 open - - open - -
2 (none) - - J 1.164 1.326
3 (none) - - H 1.487 1.783
4 (none) - - (none) - -
5 (none) - - 950FH90 0.940 -
6 prism - - close - -


Longer Infrared (IR2) Channel

11th  August 2000
Slot Wheel 10 Wheel 11
Fliter 50%
Cut
On
50%
Cut
Off
Filter 50%
Cut
On
50%
Cut
Off
1 open - - open - -
2 3.3µm (**) 3.226 3.371 Ks (*) 1.991 2.302
3 3.7µm (**) 3.611 3.723 K (*) 2.027 2.362
4 (none) - - (none) - -
5 L' (**) 3.426 4.126 Ge 1.80 -
6 prism - - close - -

(*) The BK7 glass are also mounted on same holder as a thermal blocking filter.
(**) The region longer than 2.5um on the instrument had still NOT been tested.


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Last Modification Date: 2001/03/15
Last Modification Author: Makoto Watanabe <watanabe@z.phys.nagoya-u.ac.jp>