1. Dirk Soltau Kiepenheuer-Institut für Sonnenphysik Synoptic Network Workshop, Boulder 22.-24.4.2013 1 Some General Considerations on Wide Field Telescopes

2. Basic assumptions and immediate conclusions Synoptic Network Workshop, Boulder 22.-24.4.2013 2 Detector size: 4k x 4 k pixels, 5 µm pixel size Field of view:  0.7°  2500 arcsec  pixelscale = 0.6 arcsec  image scale = 120 arcsec/mm  focal length = 1720 mm

3. Diameter Synoptic Network Workshop, Boulder 22.-24.4.2013 3  resolution according to sampling theorem: 1.2 arcsec = 5.8 µrad  D = 1.22 λ / 5.8E-6  minimum Diameter w.r.t resolution = 0.1 m

4. Bandwidth, SNR Synoptic Network Workshop, Boulder 22.-24.4.2013 4 Assumed bandwidth: 0.005 nm ( 50 mÅ) Assumed Exposure time: 0.005 s Telescope PBS Cam1 Cam2 FRet Sun

5. Counts and SNR Synoptic Network Workshop, Boulder 22.-24.4.2013 5 Aperturewavelength  λ = 5 pm Heat loadPhotoelect rons SNR 0.1 m400 nm10 W450070 0.5 m400 nm200 W110000350 1.0 m400 nm1000 W450000670 0.1 m630 nm10 W9000100 0.5 m630 nm200 W230000480 1.0 m630 nm1000 W900000950 Diameter should exceed 0,5 m  f/# < f/3.5

6. Mounting (common instrument platform) Synoptic Network Workshop, Boulder 22.-24.4.2013 6 May be we need different instruments for different SNR requirements (Polarimetry vs. imaging)  Several instruments on one platform may be a solution

7. Image Motion and Noise 7 0.1 m 1 m Sun = 10 4 isoplanatic patches  Average seeing induced image motion of the whole disk will be around 0.01 pixel 2 pixel 1 pixel

8. Time constant Synoptic Network Workshop, Boulder 22.-24.4.2013 8 0.1 m 1 m

9. Image motion: Effect on image subtraction Synoptic Network Workshop, Boulder 22.-24.4.2013 9 = -  Image stabilization needed, dual beam polarimetry desirable Example: shift by 0.1 pixel  10 -2 noise

10. Image stabilization? Synoptic Network Workshop, Boulder 22.-24.4.2013 10 Main cause probably instrumental: spatial dimensions: 1m  1 arcsec corresp. 5 µm Limb sensor vs. Correlation tracker Tiptilt mirror relay optics? Solar Orbiter (PHI) concept?

11. Optical Design Options Synoptic Network Workshop, Boulder 22.-24.4.2013 11 Design driving parameters: Detector SNR @ typical exposure time

12. Refractor Synoptic Network Workshop, Boulder 22.-24.4.2013 12 Good performance, limited diameter Example: Chrotel (KIS)

13. Example: Maksutov Synoptic Network Workshop, Boulder 22.-24.4.2013 13 + Potential for evacuation - D = 200 mm, FOV = 0.5 deg 10 µm

14. Example: Ritchey-Chretien Cassegrain Synoptic Network Workshop, Boulder 22.-24.4.2013 14 D = 600 mm, FOV = 0.5 deg -Might need a field corrector if larger -needs baffling (daylight blindness)

15. Summary Synoptic Network Workshop, Boulder 22.-24.4.2013 15 Basic requirement: SNR Image stabilization – if necessary – has large impact on the design Diameter not determined by resolution arguments  telescope doesn‘t need to be diffraction limited Evacuation should be considered (catadioptric system?) Ritchey-Chretien promising. But false light counter measures necessary

16. Photon electrons Synoptic Network Workshop, Boulder 22.-24.4.2013 16 Solar Spectral Irradiance from ASTM data in W/^m^2/nm1,700Photon energy / J3,15E-19 wavelength/nm630,000 bandwidth/nm0,005telescope area / m^27,85E-03 Telescope aperture/m0,100input power/W8,59E+00 eff. focal length / m1,800 output power w/o bandwidth e/W5,64E+00 boxwidth FOV/arcsec2000,000 telescope transmission6,56E-01 Number of mirrors0,000 mirror reflectivity0,900image scale in arcsec/mm1,15E+02 pixel scale in arcsec/pixel5,73E-01 FOV / mm1,75E+01 Number of lenses windows4,000Power within bandwidth/W8,76E-06 lens transmission0,900 Number of photons within bandwidth / arcsec^2 /s9,61E+06 Extra transmission0,250 atmospheric transmission0,800 Number of photons within bandwidth / pixel /s3,15E+06 exposure time/s0,005 Pixel size / mm0,005 Number of photon electrons within bandwidth / pixel /s2,21E+06 Quantum efficiency0,700 Number of photoelectrons1,10E+04 SNR1,05E+02