[madbadgalaxyman (Robert)]

I am pleased when I hear that people were able to clearly see the outline of the Horsehead.

It sounds like the H-beta filter actually does work on this object.

I have never tried using this filter myself;
but I can definitely say that even when I was in my prime for visual sensitivity at low light levels (when I was in my 20s) and I was regularly visually observing with a 10inch F4 Newt. under dark skies, the most I could usually see in dark sky conditions was a vague area where the sky looked a little more dark than the dark sky around it.

I could see the dark nebula here, but only as a slightly darker patch of sky than the dark sky around it! Seeing the Horsehead, unfiltered, was like comparing blacks with blacks, rather than seeing grayscale!
In unfiltered visual observations, there was never enough contrast between the Horsehead and the vanishingly faint surrounding nebulosity, to see the dark nebula clearly.

The Horsehead must be an extremely difficult object to see without a filter, because in those days I could easily see the brightest portion of Barnard's Loop in 10x50 binoculars, and I was able to see with the telescope some internal structure within the very-low-surface-brightness Barnard's Galaxy...... so when I was trying to see the Horsehead without a filter, I am quite certain that there was nothing wrong with my visual sensitivity and nothing wrong with my observing technique.

cheers, Robert

I never did try to see the Horsehead when the sky conditions were at their absolutely most perfect (dark and transparent)....because under these perfect conditions I always spent all of my time looking for internal details within galaxies. More exciting to see multiple HII regions and some dark lanes, within another galaxy, than a single small dark nebula in our own Galaxy!