Optical design of a high-spatial-resolution extreme-ultraviolet spectroheliograph for the transition region.
A spectroheliograph dedicated to the observation of the solar disk in the extreme-ultraviolet OV spectral line at 62.97 nm is described. As demonstrated in the Skylab SO-82A spectroheliograph [Appl. Opt. 16, 870 (1977)], this line is uniquely suited to characterize solar plasma in the important 250, 000 K temperature regime. No multilayer coating or suitable filter is yet available to select this wavelength, so an optical design based on a double spectrograph with a spatial filter to remove the unwanted radiation has been developed. Analysis of the optical design shows that this instrument can obtain a 1 arcsec spatial resolution (two pixels) with a relatively high image-acquisition cadence. A preliminary tolerance analysis has been performed. A simple method of instrument alignment in visible light is also described.
Naletto
Giampiero
G
Dipartimento di Ingegneria dell'Informazione, Università di Padova, Via Gradenigo 6/B, I-35131 Padova PD, Italy. naletto@dei.unipd.it
Fineschi
Silvano
S
Antonucci
Ester
E
Da Deppo
Vania
V
Nicolosi
Piergiorgio
P
Zangrilli
Luca
L
Romoli
Marco
M
Malvezzi
Marco
M
Moses
Daniel
D