Abstract

This trade study presents a summary of several COSMO Technical Notes in an effort to evaluate the relative performance of reflecting vs refracting coronagraphs. Both large aperture and very low instrumental scattered light are required to measure Gauss-level line-of-sight integrated magnetic fiel... Show moreThis trade study presents a summary of several COSMO Technical Notes in an effort to evaluate the relative performance of reflecting vs refracting coronagraphs. Both large aperture and very low instrumental scattered light are required to measure Gauss-level line-of-sight integrated magnetic fields with scientifically interesting spatial and temporal resolutions. For example, a 1.5m telescope observing with a few arc second spatial resolution and a 10-minute cadence would require the background light to be approximately 5ppm of the disk-center brightness1. Traditional coronagraphs use refracting objectives up to half a meter in diameter, yet all modern large-aperture telescopes are reflectors. The requirement for a very low level of scattered light, however, strongly favors a large refracting singlet. Our investigations have concluded that a 1.5m refracting coronagraph is feasible with modern glasses and technology. Show less