G'day,
I have a bintel 2x barlow, and in my reading I have found references where people say placing such a barlow before a diagonal will make it an effective 3x barlow. I just tried it out, with a 45 degree erecting diagonal that came with my skywatcher - doesn't seem to work. I had alpha crux in the middle of field with diagonal -> barlow 25mm, then switched to barlow -> diagonal ->25mm. The latter configuration showed me no light, not even a hint of a star.
And so I conclude that it doesn't work.
So my question is, should it have worked, or is there a specific combination of barlow/diagonal that is required?
Cheers,
Steve