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

Basic assumptions and immediate conclusions Synoptic Network Workshop, Boulder 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

Diameter Synoptic Network Workshop, Boulder  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

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

Counts and SNR Synoptic Network Workshop, Boulder Aperturewavelength  λ = 5 pm Heat loadPhotoelect rons SNR 0.1 m400 nm10 W m400 nm200 W m400 nm1000 W m630 nm10 W m630 nm200 W m630 nm1000 W Diameter should exceed 0,5 m  f/# < f/3.5

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

Image Motion and Noise 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

Time constant Synoptic Network Workshop, Boulder m 1 m

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

Image stabilization? Synoptic Network Workshop, Boulder 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?

Optical Design Options Synoptic Network Workshop, Boulder Design driving parameters: Detector typical exposure time

Refractor Synoptic Network Workshop, Boulder Good performance, limited diameter Example: Chrotel (KIS)

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

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

Summary Synoptic Network Workshop, Boulder 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

Photon electrons Synoptic Network Workshop, Boulder 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