Wheel Specifications

PHARO contains 4 wheels that carry slits, pupil masks, filters, and grisms. The elements currently installed in each wheel are listed in the following tables.

Slit Wheel

Lyot Stop Wheel

Filter Wheel

Grism Wheel

Slit Wheel
#	Name	Comment
1	0.41" Spot	coronograph mode
2	0.1" Slit	spectrograph mode
3	0.91" Spot	coronograph mode
4	0.2" Slit	spectrograph mode
5	Pinhole Grid	.
6	0.5" Slit	spectrograph mode
7	40" Field mask	imaging mode
8	2" Slit	spectrograph mode
9	25" Field mask	imaging mode
10	Occulting Bar	.

Lyot Wheel
#	Name	Comment
1	Block	.
2	Open	.
3	Std Cross	.
4	Std Cross - 45	.
5	Med Cross	.
6	Big Cross	.
7	Std Spot	.
8	Spare 2	.
9	Spare 3	.
10	Spare 2	.

Filter Wheel
#	Filter	Central Wavelength* (microns)	Bandpass (microns)	Half Power Wavelengths* (microns)	Transmission	Sensitivity	Manufacturer
1	Open	.	.	.	.	.	.
2	J	1.246	0.162	1.165 - 1.327	87.3%	.	OCLI
3	H	1.635	0.296	1.487 - 1.783	84.9%	.	OCLI
4	K	2.196	0.336	2.028 - 2.364	90.4%	.	OCLI
5	K'	2.121	0.351	1.945 - 2.296	91.8%	.	OCLI
6	K _S	2.145	0.310	1.990 - 2.300	91.8%	.	OCLI
7	Br-gamma	2.166	0.02	2.16 - 2.18	75.0%	.	Barr
8	H₂ 2-1	2.248	0.02	2.24 - 2.26	68.6%	.	Barr
9	CO (2-0 Bandhead)	2.295	0.02	2.29 - 2.31	72.0%	.	Barr
10	K_cont	2.26	0.06	2.23 - 2.29	83.0%	.	Barr

*Note: Wavelength measurements for OCLI filters were made at room temperature, not at operating temperature (77 Kelvin). Wavelengths of narrow-band Barr filters estimated from room temperature measurements shifted to wavelength of line.

Grism Wheel
#	Filter	Central Wavelength* (microns)	Bandpass (microns)	5% Power Wavelengths* (microns)	Transmission	Sensitivity	Manufacturer
1	ND-01	.	.	.	1%	.	JANOS
2	H Grism	See table below for specs on Grisms
3	Open	.	.	.	.	.	.
4	K Grism	See table below for specs on Grisms
5	Fe II	1.648	0.030	1.633 - 1.663	.	.	Barr
6	H Continuum	1.668	0.018	1.659 - 1.677	.	.	Barr
7	Open	.	.	.	.	.	.
8	Pa-beta	1.272	0.024	1.260 - 1.284	.	.	Barr
9	J Grism	See table below for specs on Grisms
10	ND-02	.	.	.	0.1%	.	JANOS

*Note: Wavelength measurements for Barr filters made at room temperature, not at operating temperature (77 Kelvin).

Grisms

# Filter Wavelength
Range*
(microns) Dispersion
(nm/pixel) Comment

2 H Grism 1.49 - 1.78 0.28467 .

4 K Grism 2.03 - 2.37 0.33215 .

9 J Grism 1.17 - 1.33 0.15771 .

Grisms
#	Filter	Wavelength Range* (microns)	Dispersion (nm/pixel)	Comment
2	H Grism	1.49 - 1.78	0.28467	.
4	K Grism	2.03 - 2.37	0.33215	.
9	J Grism	1.17 - 1.33	0.15771	.

For more information about specific manufacturers, visit the OCLI , JANOS , and BARR home pages.