Optics

The camera optical design is a single optical train that images the sky onto the focal plane at an optical speed of f/3.74, with a plate scale of 0.45"/pix at the T22. Next figure shows the optical unfolded path which is 1890 mm long from the entrance window to the detector, as well the folded solution adopted.

The camera consists of one field lens, L1, close to the RC telescope focus; and two separate groups of lenses, one, from L2 to L5, before the cold stop, and another, from L6 to L9 after the cold stop mask. Due to the mechanical constrains in length and weight we have searched for alternatives to make the system more compact. The packaging solution adopted introduces three folding flat mirrors in the optical path between L1 and L2. From the optical performance point of view this packaging proposed has not effect. The mirrors positions have been fixed for an optimum separation, avoiding interference and vignetting, in order to reduce the cold volume of the system.

 

The next table lists a summary of the characteristics that describe the performance of PANIC in both telescopes. The figures of merit that provides a rough idea about the design quality are also shown.

 

Table: T22 and T35 RC foci General capabilities and Summary of the PANIC general performance.
CAHA Telescope @ T22 RC focus @ T35 RC focus
Optics Ritchey-Chrétien Ritchey-Chrétien
Aperture diameter 2.2 m 3.5 m
Focal ratio f/8 f/10
HFOV with no vignneting 0.275º 0.245º
Cassegrain focus diameter 33’ = 170 mm 29.5’ = 300 mm
Scale at Cass. focus 11.7 ”/mm 5.89 ”/mm
PANIC performance
Direct imaging Over the whole FOV Idem
FOV 31.9’ x 31.9’ 16.4’ x 16.4’
Scale at detector 0.45 ”/px 0.23 ”/px
f/# 3.744 4.674
Pupil image mechanism

Mechanically available,

Optimized for T22

Mechanically available,

Optimized for T35
Pupil image quality < 2% loss in flux all bands Idem
Wavelength range

Optimized: 0.95 – 2.5 mm

Good transmission and IQ from 0.8 mm

 Idem
EE80 diameter

1.5 pix.= 26.4 mm= 0.66" max.

(< 2 pixels=36mm=0.90")

2.0 pix.= 35.5 mm = 0.45" max

(< 3 pixels=54mm=0.69")
Distortion < 1.4 % max. (corner) Idem
Transmission ~ 57.3% (window+9 lenses+3gold mirrors) Idem
IR Detector 4 K x 4 K Idem
Operating temperature 80 K Idem
Gap between detectors 167 pixels, < 75" < 40"
Filters

Broad band: ZYJHK

Narrow band ~1%

 Idem

 

For more details, you can see the Optics FDR document.