The F ratio of a SHS should be about F:45. Assume a 2.7 meter f.l.
telescope, a 1.9 meter f.l. spectroscope, a grating 32x30mm ruled
area with 1200 gr/mm, 5000A blazed, slits adjusted to about 0.6A
passband for H alpha. The solar disk will be comfortably bright to
study, all details will be easily seen, even very faint detail.
Eyepiece power will be about 25X. Can use 0.2A passbamd.
A SHS does not show the full diameter of the solar disk to visual
examination. Mechanical and optical factors of the solar image
synthesizer restrict the instrument to about 20 arc/min by about 30
arc/min field of view, maybe less.
The human eye has maximum sensitivity at green-yellow, call it 100%.
In the orange-red for H alpha, about 10% sensitivity. In the violet,
about one percent. Only a redesigned SHS and a young person can see
the solar disk in violet K light. The cornea of the eyes yellow with
age. The main useful wavelength is H alpha light.
For the solar continuum of the sun itself, call it 100%. The yellow
sodium lines and the Mg lines are about 8%. The H alpha line is about
16%.The violet H and K lines are about 6%. Strong telluric lines are
zero per cent.
The grating efficiency of a 5000A (green) blazed wavelength has about
80% of the light at that wavelength. For the same grating, efficiency
at violet will be about 20%. For same grating, efficiency at H alpha
will be about 40%.