Orion Ultrablock / Focal reducer

[daryl_lincoln]

Should the ultrablock filter go infront or behind my focal reducer

And does anyone had expereance with the orian ultra block as all my images have gone more to the green and is making it hard to get true colours in my images

[Ben Ritchie]

And does anyone had expereance with the orian ultra block as all my images have gone more to the green and is making it hard to get true colours in my images

The Ultrablock is effectively a narrowband filter - it only passes the H-Beta line and nearby [O III] doublet . Both of these are in the green portion of the spectrum, hence turning your images green - no other light gets through. It's really designed for emission-line nebulae, so you'll lose most of the light from stars and galaxies, only the fraction that falls at wavelengths passed by the Ultrablock will come through.