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.
CAHA Telescope |
@ T22 RC focus |
@ T35 RC focus |
|
Optics |
Ritchey-Chrétien |
Ritchey-Chrétien |
|
Aperture, Æ S1 |
2.2 m |
3.5 m |
|
Focal ratio |
f/8 |
f/10 |
|
HFOV with no vignneting |
0.275º |
0.245º |
|
Æ Cassegrain focus |
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 |
|
Image Quality, EE80 |
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 (minimum) = 75" |
40" |
|
Filters |
Broad band: ZYJHK Narrow band ~1% |
Idem |