IRTF RC2 Photometer

The IRTF RC2 Photometer ("RC2") is a single-element 1-5 micron InSb detector with passbands defined by a set of discrete filters and a circular variable filter (CVF) segment. The detector and aperture wheel are cooled by solid N2; the filters are cooled by liquid N2. The liquid nitrogen jacket must be filled twice a day. Data is recorded automatically by the IBM PC Data Aquisition System (DAS) computer, which controls filter and aperture changes remotely from the control room.

Filters and Apertures

The discrete filters available for use with RC2, and associated sensitivities, are listed below:

Filter	Lambda (µm)	Delta Lambda (µm)	Limiting Mag	Limiting Flux (µJy)
1	J (1.25)	0.30	20.5	9.6
2	H (1.65)	0.35	20.3	7.4
3	K (2.20)	0.42	19.7	8.2
4	L (3.45)	1.05	15.8	139
5	L' (3.80)	0.67	15.8	115
6	M (4.80)	0.57	12.5	1530

Notes:

• Limiting mags and fluxes are for 1 sigma detections (S/N=1) in a 6 arcsec aperture in 1 hour of integration with good sky conditions.

• The L (3.45 µm) filter has a small short wavelength leak.

• The M filter has a poor beam profile and should not be used for precise photometry.

The circular variable filters available for use with RC2 are listed below:

Wavelength Range (µm)	Resolving Power (R=lambda/dlambda)
1.3 - 2.6	30
1.9 - 3.6	100
2.8 - 5.3	50

The available apertures are circular with diameters (mm) of:

Aperture Diameters (mm)
0.5	1.0	2.0	3.0	4.0	5.0	6.0