Solar viewing - mask at eyepiece filter?

Assuming a solar Ha filter, could the image of prominences be improved
by taking a clear filter and painting a small black spot at the center.
This second filter would be added to the filter stack. The dot would
then be used to mask the Sun's disk. Would making a such disk mask out
of clear filter improve viewing of solar prominences by masking the
glare of the Sun's disk?

Is this a practical idea or are there other approaches?

- Canopus56

canopus56 wrote:
Assuming a solar Ha filter, could the image of prominences be improved
by taking a clear filter and painting a small black spot at the center.
This second filter would be added to the filter stack. The dot would
then be used to mask the Sun's disk. Would making a such disk mask out
of clear filter improve viewing of solar prominences by masking the
glare of the Sun's disk?

Is this a practical idea or are there other approaches?

- Canopus56


What a *hot* idea!

In fact, this is called the Lyot stop and used in coronagraphs.

However, not only is the image of the sun blocked, but the images of
the spider vanes and central obstruction. Diffraction around these
objects will overpower the corona. A fairly long search through goole
indicates that after comming to focus, the illuminated sun is blocked
like you say (generally with a mirror to a light dump); then the image
is recollimated, passed through the Lyot stop to clean up the rest of
the image (blocks a larger version of the actual aperture), and
refocused to its final observation point.

Mitch